Hillsborough County
Parks Tree Management
Plan
Risk Mitigation and Strategic Planting
UF/IFAS Extension
ANDREW K. KOESER, GAIL HANSEN, HUNTER THORN, DEBORAH R. HILBERT, CODY ARTZNER,
AND MALLORY LAFERRIER
GULF COAST RESEARCH AND EDUCATION CENTER, UNIVERSITY OF FLORIDA
DEPARTMENT OF ENVIRONMENTAL HORTICULTURE, UNIVERSITY OF FLORIDA
January 31, 2021
Contents
1
Introduction and Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1
Executive Summary
5
1.2
Introduction
6
1.3
How many parks were inventoried?
6
1.4
How many trees were risk assessed?
6
1.5
Who assessed the trees?
6
1.6
How do we relocate trees?
6
1.7
What risk assessment method was used?
7
1.8
What key definitions from the ISA Tree Risk Assessment BMP are needed to
understand this report?
7
1.9
Who created the planting plans?
8
1.10 How were planting spaces identified?
9
1.11 How were species selected?
9
1.12 How do we use the information gathered for guiding future management of
the trees in Hillsborough County’s parks?
9
2
Risk Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1
What tree species are found in Hillsborough County Parks?
13
2.2
What are the diameter distributions of the predominant tree species?
15
2.3
What is overall risk associated with Hillsborough County park trees?
18
4
2.4
What were the common defects observed during the risk assessments? 18
2.5
What are the projected mitigation costs?
19
2.6
How can I prioritize mitigation efforts?
25
2.7
Other threats - What pests or diseases have the potential to impact the trees
which dominate Hillsborough County Parks?
27
3
Strategic Planting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.1
How were the species and planting locations selected?
31
3.2
What are the projected tree costs?
35
3.3
How were the projected costs calculated?
35
4
Canopy Analysis and Grand Oaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.1
What is the canopy Coverage for Hillsborough County Parks?
37
4.2
How is canopy coverage measured?
37
4.3
What are the estimated ecosystem services associated with the trees in the
County Park System?
37
4.4
Where are Grand Oaks located within Hillsborough County Parks?
38
4.5
What care is needed to maintain Grand Oaks?
39
4.6
Were their any cases where Grand Oaks were recommended for removal?
40
4.7
How can we engage the Public with Grand Oaks?
40
5
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction and Executive Summary
1.1 Executive Summary
Key deliverables and findings from this effort include:
• A total of 10,917 trees were inventoried for this risk management and planting plan.
• 144 parks were included in this effort, with trees (in managed areas), structural assets, and
planting areas geolocated and mapped in the associated files included with this report.
• Mitigation budgets (pruning and removal) are included for each park inventoried and risk
assessed. We estimate a total of $197,355 in potential removals and $520,005 in potential
pruning.
• Planting designs were created and developed for 144 parks and are included in the enclosed
GIS data as data layer.
• The current diversity of the trees in the managed areas of the park system is low, with 6 species
(and just 3 genera) representing 81.5% of the trees.
• Hillsborough County Parks has an aging population of trees which is dominated my mature
specimens (with relatively fewer young trees).
• A total of 532 Grand Oaks were identified and geolocated as part of the tree risk assessment
efforts.
• In assessing the 148 parks (including 4 currently in development) provided by the County GIS
team, we calculated current system-wide canopy coverage at 40.7% (with a standard error of
1.1%).
• Given the current canopy coverage and combined acreage of the Hillsborough County Park
System, USDA Forest Service models project the trees under the department’s management
reduce healthcare costs related to respiratory ailments by $138,624, reduce storm water runoff
by nearly 10 million gallons, and sequester enough carbon annually to offset the emissions of
over 1,300 cars or over 700 homes.
• A video tutorial showing how to easily access all of this data for your specific needs is provided
here.
6
Chapter 1. Introduction and Executive Summary
1.2
Introduction
The findings of this work are intended to assist Hillsborough County Parks in the management of its
tree resource. As living infrastructure, trees represent one of the few park assets that appreciates in
value over time. That said, trees (like all structures) require periodic inspections to gauge their safety.
The two largest expenses for most urban forestry programs are removals and planting. Often
effort is taken to balance these activities to prevent annual tree deficit (i.e., a situation where more
trees are removed than are planted as part of resforestation efforts). Our inventory of existing trees
will guide tree removal and planting efforts over the coming years. To balance the loss of mature trees
lost to death and decline, the County is currently undertaking a large-scale planting initiative. We
have included a species selection guide and series of planting plans to facilitate a strategic planting
program.
In funding this effort, Hillsborough County Parks has taken a first critical step towards the
intentional and proactive management of its tree assets. Few land managers within the state have
taken such as step, making the County a leader among its peer institutions in regard to its urban
forest management efforts.
1.3 How many parks were inventoried?
In total, 144 parks and sports complexes were inventoried to assess tree risk and identify planting
spaces. Four parks (i.e., Panther Trace Park, Shadow Run Park, Tanner Road Park, and Valencia
Lakes) were excluded from our efforts as they are still in the process of being developed for use.
1.4 How many trees were risk assessed?
While our database contains records for 10,917 individual trees, many more trees were risk assessed.
All trees in maintained areas near built assets and recreational areas were inventoried if over 4 feet in
height. Trees in more natural settings/dense stands were only recorded in our inventory if they posed
a potential risk to the public.
1.5 Who assessed the trees?
All trees were risk assessed by members of the Urban Tree and Landscape Management Lab at the
University of Florida Gulf Coast Research and Education Center. The three primary risk assessors all
hold the International Society of Arboriculture (ISA) Tree Risk Assessment Qualification (TRAQ)
and have been trained to use the Quantified Tree Risk Assessment methodology. Additional inventory
assistance not related to tree risk was provided by trained lab personnel.
1.6 How do we relocate trees?
Prior to any mitigation work, trees will need to be revisited and marked for pruning or removal by
county staff. To accomplish this, we recommend using the GPS coordinates to get near the tree in
question. Once in the general location, the assessor can switch to the the aerial map to relocate the
tree. If trees are in close proximity to one another in a closed canopy grouping, a combination of
species identification and stem diameter remeasurement should be sufficient to hone in on the correct
1.7 What risk assessment method was used?
7
tree. Relocation of trees in parks is one of most daunting aspects of urban forestry reassessment given
the lack of readily available landmarks common to other site types such as residential streetscapes.
1.7 What risk assessment method was used?
All risk assessments were completed using the ISA Tree Risk Assessment BMP method (i.e., the
TRAQ form). Unless otherwise noted, park users were assumed to be the primary target. Trees near
built assets or in maintained areas were inventoried and risk assessed using a basic (i.e., 360-degree
visual) level of assessment. Trees in more natural areas or in dense stands were assessed using a
limited visual assessment (i.e., a rapid assessment from one vantage point). Only trees with the
potential to fall or drop branches into maintained areas were assessed in this manner. Of these, only
trees with likelihood of failure ratings of "probable" or "imminent" were recorded. For all trees,
only the most pressing defect with regard to safety was recorded. Other lesser risks may be present
and should be considered when pruning or otherwise mitigating the risk of a given tree. A five-year
time frame was used for this project. In the time since we settled on this time frame, the industry
has gravitated toward a narrower two-year inspection window. Future efforts to risk assess trees
may want to revisit this aspect of the scope to ensure compliance with the latest in best management
practices.
1.8 What key definitions from the ISA Tree Risk Assessment BMP are needed to
understand this report?
The ISA Tree Risk BMP has four sets of definitions related to Likelihood of Impact (i.e., will
something be struck by a falling tree or tree part), Likelihood of Failure (i.e., will the tree fall or
break apart given expected weather conditions), and Consequences of Failure (i.e., what damage
or injury would be expected if the failure did impact a target). Following the guidelines for each
of these three inputs, a final risk rating is determined and mitigation measures may or may not be
prescribed. These are listed as follows.
Likelihood of Impact:
• High - The failed tree or tree part is likely to impact the target. This is the case when there is a
constant target, with no protection factors, and the direction of fall is toward the target.
• Medium - The failed tree or tree part could impact the target, but is not expected to do so. This
is the case for people in frequently used areas when the direction of fall may or may not be
toward a target. An example of a medium likelihood of impacting people would be passengers
in a car traveling on an arterial street next to the assessed tree with a large, dead branch over
the street.
• Low - There is a slight chance that the failed tree or tree part will impact the target. This is
the case for people in an occasionally used area with no protection factors and no predictable
direction of fall; a frequently used area that is partially protected; or a constant target that
is well protected from the assessed tree. Examples are vehicles on an occasionally used
service road next to the assessed tree, or a frequently used street that has a large tree providing
protection between vehicles on the street and the assessed tree.
• Very low - The chance of the failed tree or tree part impacting the specified target is remote.
Likelihood of impact could be rated very low if the target is outside the anticipated target zone
or if occupancy is rate is rare. Another example of very low likelihood of impact is people in
8
Chapter 1. Introduction and Executive Summary
an occasionally used areas with protection against being struck by the tree failure due to the
presence of other trees or structures between the tree being assessed and the targets.
Likelihood of Failure:
• Imminent - Failure has started or is most likely to occur in the near future, even if there is no
significant wind or increased load.
• Probable - Failure may be expected under normal weather conditions within the specified time
frame.
• Possible - Failure may be expected in extreme weather conditions, but is unlikely during
normal weather conditions within the specified time frame.
• Improbable - The tree or tree part is not likely to fail during normal weather conditions and
may not fail in extreme weather conditions within the specified time frame.
Consequences of Failure:
• Severe - Consequences that could involve serious personal injury or death, high-value property
damage, or major disruption of important activities.
• Significant - Consequences that involve substantial personal injury, moderate- to high-value
property damage, or considerable disruption of activities.
• Minor - Consequences that involve minor personal injury, low- to moderate-value property
damage, or small disruption of activities.
• Negligible - Consequences that do not result in personal injury, involve low-value property
damage, or disruptions that can be replaced or repaired.
Overall Risk Rating:
• Extreme - This category applies to situations in which failure is imminent, with a high
likelihood impacting the target and having severe consequences. Mitigation measures should
be taken as soon as possible.
• High - This category applies to situations in which consequences are significant and the
likelihood of failure and impact is very likely or likely. Mitigation measures should be
recommended by the assessor.
• Moderate - This category applies to situations in which the consequences are minor and the
likelihood of failure and impact is very likely or likely. Alternatively, this category applies
to situations where the likelihood is somewhat likely and the consequences are significant or
severe. The risk assessor may or may not choose to offer mitigation suggestions.
• Low - This category applies to situations in which the consequences are negligible or minor
and/or the likelihood of failure and impact are unlikely or somewhat likely. Mitigation
measures are not generally required.
1.9 Who created the planting plans?
Planting plans were created by Dr. Gail Hansen’s lab at the University of Florida. She was assisted
by landscape architect students, Cody Artzner and Mallory LaFerrier.
1.10 How were planting spaces identified?
9
1.10 How were planting spaces identified?
Planting spaces within the parks were first identified using aerial imagery. These spaces were marked
in a Geographic Information System (GIS) as polygons (i.e., blocks where trees could be placed).
Once onsite, each planting location was assessed to identify any potential conflicts not visible from
the aerial imagery. All planting locations were then photographed to provide the design team with
additional visual information regarding the surrounding landscape.
1.11 How were species selected?
Species were selected given function, hardiness, soil moisture tolerance, and general availability
in larger sizes (to prevent loss given vandalism or mower damage). Our species list includes both
native and non-invasive introduced species (as determined by IFAS Assessment).
1.12 How do we use the information gathered for guiding future management of
the trees in Hillsborough County’s parks?
This project has generated a great deal of data for managers of the County Park system. As such,
it has the potential to serve as a crucial first step in the creation of a comprehensive management
plan1 (Fig. 1.1). If the county wishes to engage in more proactive and adaptive tree management,
reading through the following report and using the collected data to run other summary statistics of
interest can assist in the next step — identifying management goals and objectives. Examples of
goals include:
• Increasing the genetic diversity of the trees within the park system.
• Maintaining size-class diversity within the population of park trees
• Reducing risk associated with the trees within the park system.
• Maximizing the canopy for appropriate use areas within the park system.
To reach these goals, specific and measurable objectives should be established to allow for the
tracking of progress. The following could be objectives for the four goals listed above:
• In order to increase the genetic diversity of our park trees, we will be strategic in our planting
efforts to make sure that no more than 10% of our trees are of a given species by 2040.
• In an effort to increase size-class diversity and increase the number of younger, small-diameter
trees in our population, we will double the current number of 2" to 6" trees in the park system
by 2030.
• In order to reduce the risk of trees within maintained park areas, we will work through our
mitigation plan ensure no high or extreme risk trees are present in the population by 2025.
• In order to provide a shaded environment for our users, we will match plantings with removals
to ensure that no net canopy loss occurs within the park system within the next five years.
These are just a few examples of a wider range of possible goals and objectives. The examples
listed above may not reflect the desires of the park administration nor the public they represent.
Similarly, the associated objectives may not be feasible given the current state of the urban forest
managed by the County and its resources on hand. We are willing to work with Hillsborough County
1Miller, R.W. (2007) Urban Forestry: Planning and Managing Urban Greenspaces, Waveland Press, Inc., Long Grove,
Illinois, 502pp.
10
Chapter 1. Introduction and Executive Summary
officials to make the most of this data and determine what is needed to achieve the desired future
state of the trees found in the park system.
Figure 1.1: The urban forest management process (Adapted from Miller, 2007)
As shown in the objective examples bulleted above, the time frame for many management
activities is often beyond any given year. Trees are slow growing and long-lived organisms and their
management is often a prolonged endeavor. Adaptive management efforts can be broken down into
smaller milestones in order to better track progress (e.g., checking in every 5 years rather than waiting
for the end of a 30-year objective; Fig. 1.2). Each of these smaller milestones or objectives can then
be further broken down into management efforts that occur within the confines of an annual-budget
driven system (Fig. 1.2).
1.12 How do we use the information gathered for guiding future management of
the trees in Hillsborough County’s parks?
11
Figure 1.2: Breaking down a long-term strategic plan into more manageable milestones and
annual operating plans (Source: Rob Northrop).
2. Risk Management
2.1 What tree species are found in Hillsborough County Parks?
A total of 83 species were identified during our inventory of Hillsborough County’s park system
(Table 5.2 Appendix). The species present within the park system ranged from native oaks (Quercus
spp.) and pines (Pinus spp.) to introduced and invasive species (Table 5.2 Appendix). While the
range of diversity was quite robust, a significant portion of the trees inventoried (37.9%) were live
oak (Quercus virginiana; Fig. 2.1). Moreover, just 6 species (i.e., live oak (Quercus virginiana),
slash pine (Pinus elliottii), laurel oak (Quercus laurifolia), cabbage palm (Sabal palmetto), sand
live oak (Quercus geminata), and loblolly pine (Pinus taeda)) account for 81.5% of the trees in our
inventory (Fig. 2.1). This core contingent of species represents just three genera (i.e., Quercus, Pinus,
and Sabal) and three families (i.e., Fagaceae, Pinaceae and Arecaceae). As as comparative reference,
a commonly-used rule of thumb for maintaining urban tree diversity is to limit a population to no
more than 10% of a given species, 20% of a given genus, and 30% of a given family1. While the
use of the 10/20/30 rule is not without debate (many argue it may not be conservative enough), it
serves as a useful guide and goal for land managers. It is also important to note that these species
represent those found in the more managed park areas. Additional species are likely to exist in the
more natural areas of Hillsborough County’s Park System.
1Santamour, F.S. (1999). Trees for Urban Planting: Diversity, Uniformity, and Common Sense.
14
Chapter 2. Risk Management
Figure 2.1: Distribution of all species comprising more than 1% of those inventoried for the
risk assessment of Hillsborough County’s parks.
2.2 What are the diameter distributions of the predominant tree species?
15
2.2 What are the diameter distributions of the predominant tree species?
While tree diameter is an imperfect means of determining a tree’s age (e.g., the oldest known trees
are stunted bristle cone pines) it can still be a useful means of assessing the what life stages are
represented in a populations of trees. Figure 2.2 show three common scenarios for tree diameter
distributions. Type I is the most common and is an indication that a forest is actively regenerating
given the presence of many small-stemmed trees. In urban and park settings, a Type II distribution
is a sign that natural regeneration is being suppressed (generally through mowing) and planting is
occurring at a lower level than is often observed through natural reforestation.
As can be seen in the the size distributions of the five most common non-palm species, the
Hillsborough County Park System has what is considered a maturing population (Figs. 2.2 and 2.3).
Mowing is keeping natural regeneration from seed from occurring and planting is not sufficient
mimic what is commonly seen in many forest communities. The strategic use of "no mow" areas
could help increase tree cover in aging parks while also reducing maintenance demand.
Whether or not this is a cause for concern is uncertain. Conducting a canopy assessment and
monitoring over time with this method will show if tree planting efforts and existing tree growth
are sufficient to replace any trees lost by storms or removals (if that is a desired management goal).
What can be said from these distributions is that the majority of management need will be centered
on mature tree care (pruning, risk assessment, etc) with a smaller proportion of live oaks in particular
benefiting from young tree pruning to improve structure.
16
Chapter 2. Risk Management
[H]
Figure 2.2: Example of common urban tree distribution types (visual representation and cor-
responding distribution shape).
2.2 What are the diameter distributions of the predominant tree species?
17
Figure 2.3: Diameter distributions for the most common tree species found in Hillsborough
County’s parks (cabbage palm omitted as diameter does not change with age.)
18
Chapter 2. Risk Management
2.3 What is overall risk associated with Hillsborough County park trees?
Within a typical population of trees, the majority of assessed specimens will be low risk, followed by
an ever-decreasing proportion of moderate risk trees, high risk trees, and extreme risk trees. The
trees assessed for Hillsborough County Parks follow this pattern with regard to overall risk ratings.
Of the 10,917 trees given risk ratings, 10,765 trees were considered to be low risk (Table 2.1). We
did not find a single tree located in a high-traffic area that was sufficiently unsound or large enough
to warrant an extreme risk rating.
Table 2.1: Overall risk ratings for the 10,917 trees assessed via Basic Visual Assessment using
the International Society of Arboriculture Tree Risk BMP.
ISA Risk Rating Number of Trees
Extreme
0
High
4
Moderate
147
Low
10,765
This is not to say that tree related failures will not occur. In fact, 860 trees had defects which
were viewed as having an imminent likelihood of failure (Table 2.2). In general, likelihood of failure
ratings limited the overall assessed risk among the trees inventoried. Unless trees were present near
buildings, picnic areas, playgrounds, or bleachers, our likelihood of impact ratings were generally
low (i.e., near pathways) or very low (i.e., away from any asset that would attract users to the site).
Additionally, many of trees with imminent likelihood of failure ratings had dead branches. In some
cases these were large, but often they were of a size where minor or negligible consequences of
failure were anticipated.
Table 2.2: Likelihood of Failure ratings for the 10,917 trees assessed via Basic Visual Assess-
ment using the International Society of Arboriculture Tree Risk BMP.
ISA LoF Rating Number of Trees
Imminent
860
Probable
1,571
Possible
2,995
Improbable
5,490
2.4 What were the common defects observed during the risk assessments?
Given the scale of the project, we collected data solely on the most significant defect with regard to
overall risk. It is our experience with analyzing and assessing tree risk data collected prior to recent
hurricanes, that trees can have multiple defects with the vast majority of them of them being of little
concern. Table 2.3 shows the most prominent defects given this method of assessment.
2.5 What are the projected mitigation costs?
19
Dead branches were the most common defect of concern encountered (Table 2.3). Branches
must grow and sustain themselves via photosynthesis in order to maintain stability and stave of decay
through compartmentalization. As such, dead branches are generally rated as having an imminent or
probable likelihood of failure. Decay, cavities, and leans are also defects which tend to have higher
likelihood of failure ratings.
In contrast, codominant stems and multiple branches emerging from a given point on the trunk,
while defects, are less likely to fail unless combined with decay or included bark. They appear in our
data set primarily because they tend to be the worst defect present in younger trees that have not
been structurally pruned (Table 2.3). Trees found in our database with these two defect types and
"structural pruning" as a suggested mitigation measure would be good candidates for young tree
training to prevent more pressing issues later on.
Table 2.3: List of the most common defects observed when risk assessing the Hillsborough
County Park System
Defect Type
Number of Trees
Dead (tree or branches)
3,883
Codominant stems
1,116
Decay or cavity
716
Multiple branches
486
Lean
301
Broken or hanging Branch
137
Included bark
107
Infrastructure conflict
81
Excess epicormics
74
Deeply planted
56
Overextended branches
15
Cracks
3
None
3940
2.5 What are the projected mitigation costs?
Each of the 144 inventoried parks has its own pruning and removal budget (Fig. 2.5). In our
assessments of risk in the parks system, we prescribed tree removal a total of 407 times. Generally
these were standing dead trees, trees in severe decline, or significantly decayed trees. Most often
these trees, while generally of low risk given likelihood of impact, had consequences of failure
that were deemed "severe" or "significant" by the assessors. A graphical depiction of prescribed
removals across the inventoried parks is shown in Figure 2.4. In general, removal demand was driven
primarily by the size of the parks with the larger sports complexes generally having the highest counts.
20
Chapter 2. Risk Management
In Table 2.4, we break down these 407 trees by consequences of failure rating and stem diameter
to show the projected removal costs based on tree size. The total cost to remove all trees is estimated
at $197,335. Prices are computed using existing contract values from Pete and Ron’s Tree Service
and include stump grinding. A copy of the template spreadsheet for quickly tabulating pruning costs
and removal costs is included with the deliverables of this project (Fig. 2.6).
Figure 2.4: Spatial depiction of removal demand within the Hillsborough County Park Dis-
trict. Point size relates to the number of trees requiring pruning within a park.
2.5 What are the projected mitigation costs?
21
Figure 2.5: Example of summary of recommended pruning and removal (including grinding)
activities and projected costs for an example park (West Park)
Figure 2.6: Spreadsheet template developed to quickly estimate pruning and removal activi-
ties (using prices from existing County contractor).
22
Chapter 2. Risk Management
Table 2.4: Projected costs for the entire 144 inventoried parks, separated by potential conse-
quences to target and tree stem diameter class.
CoF Rating Diameter Class Tree Count
Cost
Severe
2" to 6"
18
$450
Severe
6" to 12"
84
$2,940
Severe
12" to 18"
96
$48,480
Severe
18" to 24"
44
$45,980
Severe
24" to 36"
26
$39,650
Severe
36" to 60"
12
$22,380
Severe
60"+
0
$0
Subtotal
$159,880
Significant
2" to 6"
18
$450
Significant
6" to 12"
36
$1,260
Significant
12" to 18"
22
$11,110
Significant
18" to 24"
6
$6,270
Significant
24" to 36"
6
$9,150
Significant
36" to 60"
1
$1,865
Significant
60"+
0
$0
Subtotal
$30,105
Minor
2" to 6"
15
$375
Minor
6" to 12"
8
$280
Minor
12" to 18"
8
$4,040
Minor
18" to 24"
1
$1,045
Minor
24" to 36"
0
$0
Minor
36" to 60"
0
$0
Minor
60"+
0
$0
Subtotal
$5,740
Negligible
2" to 6"
1
$25
Negligible
6" to 12"
2
$70
Negligible
12" to 18"
3
$1,515
Negligible
18" to 24"
0
$0
Negligible
24" to 36"
0
$0
Negligible
36" to 60"
0
$0
Negligible
60"+
0
$0
Subtotal
$1,610
Total
$197,335
2.5 What are the projected mitigation costs?
23
Pruning was a much more common prescribed mitigation measure. Approximately half of the
trees in the inventory could benefit from either structural pruning or crown cleaning. This comes at
an estimated cost of $520,005. We recommend looking at each individual park for more detail on
this as approaching pruning from a system-wide scale may not be feasible.
Figure 2.7: Spatial depiction of pruning demand within the Hillsborough County Park Dis-
trict. Point size relates to the number of trees requiring pruning within a park.
24
Chapter 2. Risk Management
As with the removals, we generated a park system-wide summary of projected pruning costs
separated out by consequences of failure and tree size (Table 2.5). All estimates were computed
using the contracted rates supplied by Hillsborough County.
Table 2.5: Projected costs for the entire 144 inventoried parks, separated by potential conse-
quences to target and tree stem diameter class.
CoF Rating Diameter Class Tree Count
Cost
Severe
0.1" to 1.5"
0
$0
Severe
1.6" to 2.0"
0
$0
Severe
2.1" to 2.9"
0
$0
Severe
3.0" to 3.9"
0
$0
Severe
4.0" to 5.9"
1
$25
Severe
6.0" to 8.9"
25
$1,080
Severe
9.0" to 11.9"
71
$4,907
Severe
12" to 17.9"
344
$27,440
Severe
18" to 23.9"
314
$29,066
Severe
24" to 29.9"
205
$23,101
Severe
30" to 35.9"
133
$18,633
Severe
36" to 47.9"
113
$21,696
Severe
48"+
38
$11,588
Subtotal
$137,536
Significant
0.1" to 1.5"
0
$0
Significant
1.6" to 2.0"
0
$0
Significant
2.1" to 2.9"
1
$5
Significant
3.0" to 3.9"
6
$52
Significant
4.0" to 5.9"
13
$321
Significant
6.0" to 8.9"
80
$3,455
Significant
9.0" to 11.9"
227
$15,688
Significant
12" to 17.9"
843
$67,245
Significant
18" to 23.9"
601
$55,633
Significant
24" to 29.9"
417
$46,991
Significant
30" to 35.9"
238
$33,343
Significant
36" to 47.9"
204
$39,168
Significant
48"+
44
$13,418
Subtotal
$275,319
Minor
0.1" to 1.5"
2
$6
Minor
1.6" to 2.0"
11
$41
Minor
2.1" to 2.9"
58
$301
Minor
3.0" to 3.9"
69
$597
Minor
4.0" to 5.9"
82
$2,024
Minor
6.0" to 8.9"
147
$6,349
Minor
9.0" to 11.9"
235
$16,241
Minor
12" to 17.9"
380
$30,312
Minor
18" to 23.9"
209
$19,346
Minor
24" to 29.9"
115
$12,959
2.6 How can I prioritize mitigation efforts?
25
Minor
30" to 35.9"
53
$7,425
Minor
36" to 47.9"
29
$5,568
Minor
60"+
7
$2,134
Subtotal
$103,303
Negligible
0.1" to 1.5"
3
$9
Negligible
1.6" to 2.0"
2
$7
Negligible
2.1" to 2.9"
18
$93
Negligible
3.0" to 3.9"
23
$199
Negligible
4.0" to 5.9"
20
$494
Negligible
6.0" to 8.9"
12
$518
Negligible
9.0" to 11.9"
7
$484
Negligible
12" to 17.9"
13
$1,037
Negligible
18" to 23.9"
6
$555
Negligible
24" to 29.9"
4
$451
Negligible
30" to 35.9"
0
$0
Negligible
36" to 47.9"
0
$0
Negligible
60"+
0
$0
Subtotal
$3,847
Total
$520,005
2.6 How can I prioritize mitigation efforts?
This inventory provides a large amount of data and information regarding the current risk posed by
the trees in the Hillsborough County Park district. We have identified a number of trees that are
likely to fail in the coming years. However, our overall risk ratings remain relatively low given the
perceived likelihood of impact among the assessors. That said, our assessments are influenced by
the timing of the inventories (i.e., during business hours, on weekdays, during a pandemic). As
managers of the park system, you may have a fuller appreciation of events and activities that increase
site occupancy during the evening hours, on weekends, and throughout the year.
If this is the case, prioritization of mitigation may benefit from drilling down beyond the overall
risk ratings. While Likelihood of Impact did change for some locations (e.g., main entrances,
bleachers, etc.), this factor was largely static for the majority of trees. As such, prioritization of risk
management activities may be most effective if focused primarily on the Likelihood of Failure and
Consequences of Failure Ratings. Table 3.1 shows how a potential breakdown of trees by these two
factors.
26
Chapter 2. Risk Management
Table 2.6: Breakdown of the most severe ratings of Likelihood of Failure and Consequences
of Failure.
Probable
Imminent
Signficant
819
449
Severe
379
273
Recognizing that it may be more efficient to tackle mitigation park by park, we have provided
pruning and removal budgets in this manner (Fig. 2.5). Prioritization of parks could be conducted
any number of ways (e.g. geographically, by number of trees to mitigate, by park usage, etc.),
filtering the master tree list as appropriate (Fig. 2.8).
2.7 Other threats - What pests or diseases have the potential to impact the trees
which dominate Hillsborough County Parks?
27
Figure 2.8: Base data used to estimate mitigation demand and pruning/removal costs).
2.7 Other threats - What pests or diseases have the potential to impact the trees
which dominate Hillsborough County Parks?
While tree risk is often framed as the potential threats trees pose to nearby targets (i.e. people,
property, and structures), urban tree risk management includes preparing for potential biotic agents
such as insects and disease. Many of the most virulent pests are host specific, attacking trees of a
specific genus of family. Examples of this include emerald ash borer and, more locally, bay wilt.
Other biotic agents are more general such as Asian longhorn beetle or lethal bronzing. Looking at
the most common species inventoried, the following are potential threats (Source: IFAS/UF IFAS
Southern Tree Factsheet series).
Pinus palustris – Longleaf pine can be afflicted by wood borers, sawflies, pine-shoot moth, and
pine weevils. Pine bark beetles can be found attacking old stressed trees.
Pinus elliottii – Slash pine can be afflicted by numerous pests. These include bark beetles and
wood borers such as the IPS beetle, turpentine beetle, and southern pine beetle. Pine tip moths also
attack this species. Sawflies can cause rapid defoliation of branches when present in large numbers
without intervention. Pine needle miner, pine needle scale, pine tortoise scale and spruce mites
28
Chapter 2. Risk Management
are all pests that target the foliage of this tree. Pine spittle bug also attack the species and can be
identified by self-created masses of foam created by nymphs.
Slash pine is susceptible to fusiform rust and prone to pitch cankers. The latter is more significant
when trees are located in managed landscaped that are fertilized with nitrogen. Needle cast can occur,
and while not necessary a problem in its own right, the disease can make a tree more vulnerable to
other infections. Finally, the species is susceptible to diplodia.
Pinus taeda – Loblolly pine can be afflicted by pine bark beetle, wood borers, pine tip moth, and
sawflies. With regard to diseases, loblolly pine is susceptible to fusiform rust.
Quercus geminata – Sand live oak is generally free of serious pests. Mites, scales and aphids
can affect foliage. Boring insects can be found stressed and weakened specimens. Cosmetic galls
may affect various parts of the tree. Sand live oak can be susceptible oak wilt (a lethal disease)
however this disease is not common in Florida at this time. Similarly, Shoestring root rot can afflict
this species from the roots eventually killing the tree’s cambium. The species can suffer from woody
cankers, but these can be pruned out. Leaf spots and powdery mildew can appear on leaves.
Quercus laurifolia – Laurel oak has few serious pests. Mites, scales, aphids, boring insects, and
caterpillars can all attack the species. The tree may produce galls Gall wasps, twig pruners, spider
mites, lace bugs, and leaf miners can afflict this species as well. With regard to diseases, root rot and
leaf blister may affect the species, particularly during wet seasons. Shoestring root rot can kill parts
of the cambium or the entire tree. Prevention is the only effective strategy. Canker diseases attack
woody parts of the tree, but can be managed by pruning. Numerous fungi can affect leaves such as
Tubakia spp. leafspot and powdery mildew. Chlorosis can occur in leaves due to low iron in high pH
soils.
Quercus virginiana – Live oak can be host to mites, scales, aphids and boring insects. However,
few of these pests are ever problematic. Galls are common on oaks but are harmless and pruned off
if desired. Live oak is susceptible to the lethal oak wilt disease. Luckily, oak wilt is not common in
Florida at this time, but this is something the county should be aware of given its abundance of oak.
Other diseases that can afflict live oak include powdery mildew and the lethal shoestring root rot.
Cankers may affect branches but can be controlled through pruning.
Sabal palmetto – Cabbage palm is susceptible to palmetto weevil, particularly after transplanting.
With regard to diseases, ganoderma butt rot can spread in the lower trunk, eventually producing
brown and white shelf-like conks. Thielaviopsis trunk rot can result from a fungal infection, espe-
cially at planting as it required a wound to enter the trunk. It is usually not detected until causing
collapse in the crown. Lethal Bronzing Disease is a relatively recent and lethal disease of cabbage
palm. The disease is spread through phloem-feeding insects and results in a rapid decline in tree
health.
2.7 Other threats - What pests or diseases have the potential to impact the trees
which dominate Hillsborough County Parks?
29
Taxodium distichum – While relatively pest free, baldcypress can be attacked by bagworms and
mites. The species is also host to the Cypress twig gall midge which creates white galls throughout
the canopy. With regard to diseases, baldcypress can suffer from twig blight and other fungi that
attack stressed or dead branch tips. Pruning and removal of diseased foliage reduce or eliminate
infection.
Ulmus alata – Winged elm can suffer from mite damage to foliage. Scale insects may be found
along twigs and branches. The greatest potential threat to Winged elm is Dutch elm disease (a lethal
affliction) and, although cases remain rare in Florida, care should be taken to avoid over planting
(10/20/30 rule). Additionally, powdery mildew can affect the leaves, but is largely cosmetic.
3. Strategic Planting
3.1 How were the species and planting locations selected?
A tree planting plan was created for each Hillsborough County park that was assessed for risk
management (Fig. 3.1) using ArcGIS/ArcMap v.10.6.1 (Esri, 2018). A tree selection guide was
developed to make the selection process more efficacious. In creating this plan, 10 location-based
categories were established:
• Buildings and Structure: character
• Open Spaces: shade
• Parking Lots: shade
• Playgrounds: sensory stimuli
• Playgrounds: shade
• Sports Fields: shade
• Sports Fields: buffer
• Walkways: character
• Walkways: shade
• Wetlands: habitat
For each category, we provides details on general characteristics, desirable attributes, negative
attributes, areas for use, and areas to avoid. Three species are suggested for use and four companion
species are offered as supplementation (Fig. 3.1). When appropriate, categories are suggested if
associated plant suggestions are applicable (i.e., “Sports Fields: buffer,” which suggests two wetland
species, is recommended for a water detention basin area).
32
Chapter 3. Strategic Planting
Figure 3.1: Extracted page from the tree selection guide.
3.1 How were the species and planting locations selected?
33
Map points were placed within GIS software to mark the proposed location of each recommended
tree (Fig. 3.2). Parks were assessed using the GIS software, making use of field notes, as well as
previously recommended planting points and planting areas provided by the field team. Supplemental
pictures, taken by the field team, were reviewed for recommended areas and points, and point
placement was modified at the discretion of landscape designers. Additional points were placed
in areas where designers determined trees might be beneficial. Each tree point is associated with
multiple fields of data within the GIS layer’s attribute table. This data includes GPS coordinates,
park identification information, tree selection guide recommendations, and a single letter identifier
(A-J), which corresponds to a specific selection guide category. Upon the completed placement of
tree points for numerous parks, all digital modifications were saved, and the layer data exported as
a shapefile (.shp). All shapefiles are included with the supplemental materials accompanying this
report.
34
Chapter 3. Strategic Planting
Figure 3.2: Example of a completed park; each pink, circular point represents one recom-
mended tree to be planted.
3.2 What are the projected tree costs?
35
3.2 What are the projected tree costs?
Total projected tree costs are listed in the Table below. A complete, park-by-park breakdown is
included in the final data (omitted here given size).
Table 3.1: Breakdown of projected tree costs across the Hillsborough County Park system
(plant material cost only, refer to existing contracts for installation and early care rates).
Tree Type
Min Cost ($) Mid Cost ($) Max Cost ($)
Buildings and Structure: character
$14,170
$19,983
$25,796
Open Spaces: shade
$22,923
$48,050
$73,178
Parking Lots: shade
$12,000
$26,667
$53,600
Playgrounds: sensory stimuli
$6,458
$20,449
$34,440
Playgrounds: shade
$14,403
$27,365
$40,327
Sports Fields: buffer
$28,386
$77,677
$126,969
Sports Fields: shade
$37,605
$87,383
$137,161
Walkways: character
$23,280
$38,315
$65,475
Walkways: shade
$51,160
$130,032
$208,903
Wetlands: habitat
$21,708
$29,705
$37,703
Total
$232,093
$505,626
$803,552
3.3 How were the projected costs calculated?
There are many factors that ultimately determine the price of a tree. These include the species
selected, the source nursery, the size, and the method of production. As such, pinning down an exact
cost to plant each park was not possible. Rather, we provide a range of costs to assist the County in
its budgeting efforts.
All prices come from stock currently available through the wholesale database, PlantAnt. We
limited our search to Florida nurseries and priced for 30 gallon or 2-inch trees whenever possible.
For some species, smaller stock were included (e.g. 15 gallon or 1-inch) if no larger alternatives
were available. When available, three different prices were included for each species (e.g., highest
price, lowest price, mid-range price) and combined to create an range for each group.
We have included a spreadsheet with the tallies of all the trees specified for planting (Fig. 3.3).
The rows of this spreadsheet correspond to each of the parks included in this project. The tallies are
further divided vertically by the various location/use categories noted above.
Below our tally of trees is a detailed price list for each park. The prices used to generate these
projected costs are listed above this table. They can be easily adjusted if needed to reflect changes in
costs over time or to match prices specific to existing suppliers.
36
Chapter 3. Strategic Planting
Figure 3.3: Summary of trees specified for each park (separated by tree group).
Figure 3.4: Projected planting costs (expressed as a range from minimum, midpoint, and
maximum price seen on PlantAnt) tallied by park and by tree group.
4. Canopy Analysis and Grand Oaks
4.1 What is the canopy Coverage for Hillsborough County Parks?
Canopy coverage is the proportion of a property, city, or other defined area that is under tree cover.
We determined that Hillsborough County has 40.7% canopy coverage averaged across all 2577 acres
of its parks included in this project (see Appendix 5.1). The standard error for our estimate of canopy
coverage was 1.1%
4.2 How is canopy coverage measured?
A total of 2000 random points were placed on aerial imagery (2019 Orthostatic NAIP imagery)
within the park boundaries. A trained interpreter moved point by point to see if a tree was present at
each randomized location. Once all points had been assessed, the total that landed on trees (814)
were divided by the total in the sample (2000) to calculate percent canopy coverage.
4.3 What are the estimated ecosystem services associated with the trees in the
County Park System?
Trees provide a range of environmental, social, and economic benefits to the the public. These
are broadly classified as ecosystem services and are often directly related to the amount of canopy
coverage found at a location. Using the methods developed by the USDA Forest Service for it i-Tree
Canopy model, we estimate that the trees managed by the Hillsborough County Park System:
• Reduce healthcare costs related to respiratory ailments by $138,624 given the filtration of
air pollutants (i.e., carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, and airborne
particulates).
• Reduce storm water runoff by nearly 10 million gallons - the equivalent of 15 Olympic
swimming pools.
• Sequester enough carbon annually to offset the emissions of over 1,300 cars or over 700
homes.
38
Chapter 4. Canopy Analysis and Grand Oaks
4.4 Where are Grand Oaks located within Hillsborough County Parks?
In assessing the Hillsborough County parks system, we encountered 532 grand oaks. Grand oaks are
defined as such given their genus (i.e., Quercus spp.), size (i.e., stem diameter and crown spread),
and condition (i.e., health and structural integrity). Within our main tree data set, one can filter out a
complete list of grand oaks by selecting all records in the GrandTree column which have a "Yes" entry.
Grand oaks are located throughout the county parks system (Fig. 4.1), with individual parks
having as many 28 of these large specimens within their boundaries. The top 10 parks where one
can appreciate multiple specimens of these aged trees are:
• Antioch Sports Complex
• Bealsville Community Center and Sports Complex
• Bloomingdale Sports Complex
• Brandon Community Center and Sports Complex
• Country Run Park
• Davis Park
• Evans Park Community Center and Sports Complex
• Limona Park
• Palm River Park and Community Center
• Thonotosassa Park and Community Center
4.5 What care is needed to maintain Grand Oaks?
39
Figure 4.1: Distribution of Grand Oaks (n=532) within the Hillsborough County Park System.
Larger circles represent parks with a greater number of Grand Oaks. The top 10 parks with
regard to number of Grand Oaks are labeled.
4.5 What care is needed to maintain Grand Oaks?
As mature trees, the care that is needed to maintain these large specimens is limited. Pruning should
largely be limited to crown cleaning to maintain safety within the fall zone of the tree. Cutting of live
branches should be minimal and limited to small diameter branches at the edges of the tree’s canopy.
In some cases, reduction pruning may be advisable for trees with a compromised trunk or root system.
Several of the trees have "monitor" as the prescribed mitigation. These may be trees with
declining health or with defects where the severity has yet to be determined (e.g., the tree could grow
to the point where the risks are negligible or continue on a spiral of decline). With time, the correct
course of mitigation action may become more readily apparent.
In cases where decline is visible, reducing stress through mulching may reduce issues related to
mower damage and soil compaction. Big trees can be a draw for visitors who may "love trees to
40
Chapter 4. Canopy Analysis and Grand Oaks
death" as they walk around them in admiration. In some cases, application of the growth regulator
paclobutrazol help reduce tree decline by slowing crown growth, enhancing root growth, and
promoting certain pest resistances. While success is never guaranteed, this plant growth regulator is
among the most researched and the cost of treatment is a fraction of the cost of the loss and removal
of a large tree.
4.6 Were their any cases where Grand Oaks were recommended for removal?
Of the 532 grand oaks identified, 5 were ultimately recommended for removal. As with all removals,
we recommend that someone within the park system first inspect the trees and make sure they
agree with the prescribed mitigation before making a final decision on the fate of these trees.
In all five cases, the oaks in questions were large, hollow laurel oak (Quercus laurifolia) that must
have been sufficiently healthy to overcome the points lost given their compromised structural integrity.
These five trees are located at four parks:
• Brandon Community Center and Sports Complex
• Evans Park Community Center and Sports Complex
• Limona Park
• Skyway Sports Complex
4.7 How can we engage the Public with Grand Oaks?
The park system’s grand oaks are a treasure. These trees are the genetic lottery winners of their kind.
They survived as acorns when millions of others were eaten, fell on poor soil, or failed to germinate
given inherent defect. They survived as seedlings and saplings when they were most susceptible
to shading and mechanical damage. As mature specimens they were spared from lethal lightning
strikes and the march of development.
We feel there is significant potential to engage the public with these trees in a concerted public
relations campaign. As discussed, the owl project proposed by the County could pair well with
efforts to highlight these amazing trees. Similarly, a public naming campaign (where the County
exerts control over the candidate names prior to voting), could raise awareness and appreciation for
both the parks and the trees that inhabit them.
4.7 How can we engage the Public with Grand Oaks?
41
Figure 4.2: The named and plaqued "Elf Tree" of Safety Harbor, Florida.
5. Appendix
Table 5.1: Complete list of inventoried parks for this project.
Alexander Park
All People’s Life Center
All Person’s Rotary Park
Antioch Sports Complex
Apollo Beach Park and Community Center
Audrey Lane Park
Balm Park and Community Center
Beacon Meadows Park
Bealsville Community Center and Sports Complex
Bethune Park and Community Center
Bloomingdale East Park
Bloomingdale Hills Park
Bloomingdale Sports Complex
Bloomingdale West Park and Community Center
Boyette Springs Park
Branchton Park
Brandon Community Center and Sports Complex
Buckthorn Park
Bullard Park
Burnett Sports Complex
Bypass Canal Park
Cacciatore Park
Calusa Trace Park
Carolyn Meeker Dog Park
Carrollwood Cultural Center
Carrollwood Meadows Park and Community Center
Carrollwood Community Park
Causeway Park
Chandler Park
Church Park
Citrus Park Sports Complex
Clayton Lake Sports Complex
Country Place Park and Community Center
Country Place Park East
Country Place Park West
Country Run Park
Cross Creek Park
Davis Park
Deerfield Park
Don Hardy park
Dover Community Center and Sports Complex
E.L. Bing Sports Complex and Airport
Earl Simmons Park and Community Center
Eber Sports Complex
Ed Radice Sports Complex
Egypt Lake Park and Community Center
Emanuel P. Johnson Community Center
Evans Park Community Center and Sports Complex
Fawn Ridge Park
FishHawk Sports Complex
Front Street Park
Gardenville Park and Community Center
George Russell Park
Hamilton Park
Hamner Tower Park
Hampton Park
Heather Lakes Sports Complex
Jackson Springs Park and Community Center
44
Chapter 5. Appendix
J.B. Gibson Park and Community Center
J.C. Handley Sports Complex
Jean Street Park
Kenly Park and Community Center
Keystone Park and Community Center
Keysville Park and Community Center
Keith Waller Sports Complex
King’s Forest Park and Community Center
Lakeview Village Park
Lakewood Park
Larry Sanders Sports Complex
Limona Park
Lucy Dell Community Pond
Lucy Dell Park
Lutz Civic Center
Lutz School House
Mango Park and Community Center
Mann-Wagnon Memorial Park
Monterey Lakeside Park
Morgan woods Community Center
Morgan Woods Community Center
Mort Park and Community Center
Mosaic Park
New Tampa Sports Complex
North Brandon Sports Complex
Northdale Park and Community Center
Northdale Sports Complex
Northlakes Community Center and Sports Complex
Northwest County Dog Park
Nuccio Park and Community Center
Nye Park and Community Center
Orange Grove Sports Complex
Oscar Cooler Sports Complex
Palm River Park and Community Center
Paul Sanders Park
Perrone Park and Community Center
Peterson Road Park
Pinecrest Sports Complex
Progress Village Community Center and Sports Complex
Providence East Sports Complex
Providence West Community Center and Sports Complex
Riverview Civic Center and Boat Ramp
Riverview Park and Community Center
Rodney Colson Sports Complex
Roy Haynes Park and Community Center
Roy Henley Park
Rubin Padgett Sports Complex
Ruskin Park and Community Center
Saladino Park
Seffner Park and Community Civic Center
Seffner-Mango Park
Shimberg Sports Complex
Simmons Bowers Park
Skyway Sports Complex
South Pointe Park
Springhead Park and Community Center
Stearns Road Park
Stephen J. Wotham Park
Sterling Height Park and Community Center
Sterling Ranch Park
Summerfield Sports Complex
Sun City Heritage Park
Sweetwater Park
Temple Park and Community Center
Thatcher Park and Community Center
Thonotosassa Main Street Park
Thonotosassa Park and Community Center
Thonotosassa School Park
Timberlan Park
Timberlane Park and Community Center
Town ’n Country Park and Community Center
Turkey Creek Sports Complex
University Area Park and Community Center
Valrico Community Center and Sports Complex
Vance Vogel Sports Complex
Villa Rosa Park
Vista Gardens Park
West Park Sports Complex and Dog Park
Westchase Community Center
Westgate Park
Westwood Lakes Park
William Owens Pass Sports Complex
Wimauma Park and Community Center
Winston Park and Community Center
Woodlake Park
45
Table 5.2: Complete list of species identified during the inventory and risk assessment of
managed areas within the Hillsborough County Park System.
Acacia spp.
Acer floridanum*
Acer rubrum*
Araucaria heterophylla
Betula nigra*
Bismarckia nobilis
Broussonetia papyrifera
Callistemon viminalis**
Carya glabra*
Carya illinoensis*
Casuarina equisetifolia**
Casuarina sp.**
Celtis laevigata*
Cinnamomum camphora**
Citrus spp.
Corymbia torelliana
Dalbergia sissoo
Elaeocarpus decipiens
Enterolobium cyclocarpum
Eriobotrya japonica
Eucalyptus spp.
Ficus aurea*
Ficus spp.
Fraxinus pennsylvanica*
Grevillea robusta
Ilex cassine*
Ilex vomitoria*
Ilex x attenuata*
Juniperus virginiana*
Koelreuteria elegans
Lagerstroemia indica
Leucaena leucocephala**
Ligustrum japonicum
Liquidambar styraciflua*
Livistona chinensis
Magnolia grandiflora*
Magnolia virginiana*
Melaleuca quinquenervia**
Melia azedarach**
Moringa oliefera
Morus alba*
Myrcianthes fragrans*
Myrica cerifera*
Nolina recurvata
Peltophorum pterocarpum
Phoenix canariensis
Phoenix dactylifera
Phoenix sylvestris
Pinus clausa*
Pinus elliottii*
Pinus palustris*
Pinus taeda*
Platanus occidentalis*
Platycladus orientalis
Podocarpus macrophyllus
Pouteria sapota
Prunus angustifolia*
Prunus caroliniana*
Prunus serotina*
Pyrus calleryana**
Quercus geminata*
Quercus laevis
Quercus laurifolia*
Quercus michauxii*
Quercus myrtilfolia*
Quercus nigra*
Quercus shumardii*
Quercus virginiana*
Rhus copallinum*
Sabal palmetto*
Schefflera actinophylla**
Syagrus romanzoffiana
Tabebuia chrysantha
Tabebuia heterophylla
Tabebuia spp.
Taxodium ascendens*
Taxodium distichum*
Triadica sebifera**
Ulmus alata*
Ulmus americana*
Ulmus parvifolia
Viburnum obovatum*
Washingtonia robusta
Species followed by "*" are Florida native species. Species followed by "**" are listed as "invasive" or "prohibited" by
UF/IFAS Assessment.