The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
Guide to "i
acting Existing Vegetation
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences
University of Florida / John T. Woeste, Dean
A GUIDE TO SELECTING EXISTING VEGETATION
FOR LOW-ENERGY LANDSCAPES
Commonly, Florida homeowners overlook the beauty and useful-
ness of the natural landscape. Each year thousands of people move to
Florida and transform a home lot into an exotic garden. The trans-
formation is not only expensive to implement, but a great amount of
energy is expended in maintenance. Additionally, the beauty of the
natural landscape is marred.
The benefits from trees and other native vegetation are not limited
to rural areas. Their importance in urban areas is recognized today
more than ever. Among other benefits, they provide esthetic settings,
cooling shade, and protection from wind, dust, and noise. Landscap-
ing with plants that would grow naturally without energy subsidy
requires a minimum of supplemental care. This practice conserves
energy by limiting the need for pesticides, fertilizers and water, all of
which require fossil fuels for processing and delivery. It also helps
protect the balance of natural systems and living organisms that
depend on a natural environment.
Developers and builders are increasingly aware of protecting and
using much of the natural beauty of the landscape during the de-
velopment and building process. In many instances, using existing
vegetation has increased the value of the site, reduced initial land-
scaping costs, and contributed to low-energy and low-maintenance
In other instances however, homeowners and developers have
found that many native species decline and perish, within a few
years, regardless of noble attempts to select and protect the specimen
native plants during construction.Under these conditions, the own-
ers and the builders have found the trees and associated vegetation to
be liabilities. Trees that appeared to have potential in contributing to
the site have, in fact. become unsightly, unhealthy, and hazardous.
All efforts to increase the site value, reduce landscaping costs and
energy consumption are offset by the high costs of tree removal and
other property damages directly related to the existing native vege-
Leaving too many trees around buildings contributes to mildew,
mold, and moisture problems inside and outside the structure.
Periodic drying by the sun and wind is important, especially in
Florida. A structure densely shaded, year-round, may cause the own-
ers to use more energy! Electric lights, which may not be needed
otherwise during daylight hours, become essential. Maintenance
'D. Mitchell Flinchum is Assistant Professor and Extension Forest Manage-
ment Specialist, School of Forest Resources and Conservation, Institute of
Food and Agricultural Sciences (IFAS), University of Florida, Gainesville,
costs on wooden structures may be higher. The use of air conditioning
to reduce high levels of humidity created by surrounding vegetation
may become more prevalent. All of these energy-consumptive ac-
tivities may be related to the lack of periodic drying by the sun and
Existing vegetation can be helpful to the low-energy, low-
maintenance landscaping concept. It may also be harmful and energy
comsumptive. The key, then, is to use the information that is cur-
rently available to take optimum advantage of the benefits that may
be derived from the natural communities on each site.
Trees in a Natural Setting
Trees and associated vegetation that have grown and developed in
a native community are quite different from trees of the same species
that developed in the open. The mature forest tree is an outstanding
example of the interaction between the hereditary characteristics of
an organism and its environment. The total environment of the tree
is a complex integration of numerous interrelated physical and
Competition for sunlight, nutrients, water, and space between
individuals of the same species and among different species, plays a
large part in the physical appearance of a tree in its natural setting.
When released from this competition, or when the elements of the
competition change, as would be expected during construction and
development, an individual tree may respond in an entirely different
way from what one might expect. Growth rates may increase and the
tree crowns may exhibit unexpected branching habits. The root sys-
tem, which supported the tree in its natural setting, may no longer be
adequate for anchorage; finally, the increased amount of sunlight
may have harmful effects on some species. Along coastal areas
changes in air currents may also have positive or negative affects on
the native species.
The impact of a change in environment seldom can be related
directly to a single measurable factor. Complex and subtle interrela-
tionships between the various factors of the environment usually
preclude any such simple cause-and-effect answer. But it is useful to
know how, in general, a plant may respond to various factors.
Because of the complexity of the total environment and the diffi-
culty with which some factors are measured, complete and exact
quantification of the environment is practically impossible. While
there are exceptions to every rule, the following guidelines should be
considered when selecting trees to be left on new building sites.
1. Leave as many Undisturbed Natural Areas as You Can.
The chances of your trees surviving will be much higher. A natural
area also contributes to a low maintenance, energy conservation
Figure 1. The natural area In the landscape at the top maintains itself to a large degree on the
energy it captures and recycles.
landscape. It not only maintains itself on the energy it captures and
recycles, but it also provides energy for a complex association of
interacting, inter-related living organisms (Figure 1). Choosing the
energy efficiency and productivity of a native landscape is not only
practical but it requires no sacrifice of beauty and diversity, as is
often suggested. A setting of native trees and shrubs grown formally
can look very neat and appealing without demanding care. A well
designed native landscape, once established, will require limited
maintenance and look the way it is naturally supposed to look. A wide
range of color, plant form and foliage texture is available to the
natural gardener who takes the initiative to learn about native
2. If You Select Individual Trees, Select Those That Live
All trees eventually die, but some die sooner than others. In the
South, live oak (Quercus virginiana Mill.) generally lives longer than
most other species. Live oaks grow on a wide variety of soils, and it is
present in nearly every habitat throughout the state. It is hardy,
strong, and while many diseases and insects may attack the tree, it
nearly always seems to survive. Construction activities appear to
have only minor effects on the growth or survival. Young live oaks,
when released from the competition of the native surrounding, grow
very rapidly. Nutrients from normal turf maintenance generally
promotes additional growth. If, per chance, the tops are killed or
damaged severely during construction, live oak will sprout abun-
dantly from the root collar and roots. Every root that is near the
ground surface ends up with three or four sprouts. These sprouts may
be protected to result in a small community of live oaks that will grow
quickly because of the already established root system. Those stems
that are less desirable may be cut to favor the more vigorous sprouts
which may soon develop into a well formed tree. When all sprouts are
cut or mowed, new ones appear in even greater numbers. The total
effect is that of a shrubby ground cover.
Mature laurel oaks and water oaks should not be selected. Because
of their short lives, relative to the life of a building, the smart owner
would not allow these species to become overmature, and would never
select a mature specimen to leave on the building site. Besides living
only 50-60 years, laurel, water and willow oaks are the three most
susceptible alternate hosts for fusiform rust of southern pines. The
alternate stage of this fungus does not seriously harm these oak
hosts; however, their presence may contribute to the decline of
nearby pines (Figure 2).
Figure 2. Identifiable traits of live oak, water oak, and laurel oak. If the choice exists,
live oak would be the best species to leave on the building site.
3. Don't Leave Unhealthy Trees.
Fusiform rust is a common disease on southern pines in north
Florida. Occurrence of the disease may be recognized by gall forma-
tions on the limbs and trunk (Figure 3). Generally, limb galls will
pose no major problems, unless the gall is within one foot of the main
stem. If the limb gall is less than one foot from the main stem, the
chance is great that the disease will move into the trunk. Limb galls
may be pruned to arrest the individual infection areas, but little can
be done for trunk galls. Large galls on the trunk may weaken or even
kill the tree. Even if the trunk-infested trees survive the stress of
construction activities, they are susceptible to breakage.
', *, > J.-.y
Figure 3. Fusiform rust galls on pines and heartrot symptoms on hardwoods indicate po-
tential problem trees.
4. Select Trees That Have Good Form, or at Least Those That
The symmetry of the crown depends greatly upon the evenness of
exposure to light. Most trees, if heavily shaded on one side, will tend
to grow poorly on that side. Live oak will respond favorably to a
release from shade and generally will develop a symmetrical, full
crown. Turkey oak, on the other hand, tends to develop new lateral
branches along the majority of the trunk. The crown form exhibited
by a mature turkey or southern red oak at the time of selection is the
best form it will ever exhibit. Don't expect these species to respond by
developing a symmetrical crown (Figure 4 ).
Figure 4. Turkey oak (Quercus laevis Walter) develops foliage along the trunk when it is
released from competition of its native surroundings.
5. Leave as Much Natural Duff as Possible Around the Base of
Removal of native duff and litter not only disturbs the natural
nutrient cycling which is important for tree growth and survival, but
the activity itself may severely damage roots that are near the
ground surface. Additionally, litter removal contributes to a rise in
the temperature of exposed soil, which may have lethal effects on the
tree (Figure 5). Very little research has been conducted on this topic,
but it is believed that soil temperatures above 95 F retards root
growth and development of loblolly pine.
On some sandy sites in Florida, soils that were partially shaded by
native vegetation have reached temperatures exceeding 165 F. It is
highly probable that soils exposed, due to duff and litter removal may
reach temperatures that are lethal to many species.
Figure 5. A combination of effects resulting from litter and duff removal activities may
prove lethal to many species.
6. Think About How the Construction Disturbances May
Modify Air Currents.
This is particularly important along the coast where salt spray
contributes heavily to the species composition and form of the native
plant community. In many maritime communities the live oak is the
dominant species, intermingled with laurel oak. Although more salt
tolerant than other species, the "pruned" umbrella form of the live
oak results from salt-spray dieback of young tender growth that is not
protected by the mature, salt-tolerant foliage. The umbrella-like
form protects the less vigorous laurel oak from being killed by salt
spray (Figure 6).
Primary Dune Secondary Dune Maritime Forest
Figure 6. Salt concentrations and wind patterns play a large role in the species composi-
tion and form of coastal communities.
Many developers have recognized the beauty of the maritime com-
munity and attempts have been made to incorporate the com-
munities into the development design. In one coastal development
project, high rise condominiums were built behind the sloping canopy
of the maritime forest. The presence of the building modified the
salt-spray patterns. As a result, the "salt-pruned" umbrella form was
changed. Rapid vertical growth obstructed the ocean view of the first
floor occupants (Figure 7). The sudden growth of the live oak
branches, stimlulated by normal lawn maintenance activities and
the modified salt-spray pattern, has caused considerable energy-
consumptive maintenance problems.
Figure 7. Crown forms altered as a result of modified salt-spray patterns.
7. Constructing a Concrete or Brick Tree Well to Protect Indi-
vidual Trees is Risky and Costly.
The wells also require energy consumptive maintenance as long as
they exist. In many cases it is necessary to construct tree-wells to
protect and save individual trees from modifications in grade and
drainage. Permanent wells, constructed of concrete or brick, will
always comsume time and energy in maintenance.
Tree wells can be constructed of non-treated, naturally durable
wood that will last for several years, and at the same time eventually
decrease the maintenance that would be required for permanent
wells. During the initial stages the maintenance requirements would
be similar to the concrete or brick wells. Over time, however, the slow
decay of the wooden well will encourage a gradual fill. The gradual
fill, which in many cases would imitate natural processes, allows the
tree to adjust to the changing environment (Figure 8). The decaying
organic matter would increase the moisture retention and nutrient-
holding capacities of the soil around the tree. Eventually the well
would fill to grade level, eliminating the need for time and energy
S ^ -Wood
Figure 8. Over time, tree wells constructed from untreated wood will reduce mainte-
nance and energy consumption.
Landscaping with plants that would grow naturally without
energy subsidy requires a minimum of supplemental care. This prac-
tice conserves energy by limiting the need for pesticides, fertilizers
and water, all of which require fossil fuels for processing and delivery.
Existing vegetation can be helpful to the low-energy, low-
maintenance landscaping concept. It may also be harmful and energy
consumptive. The key is to use the information that is available to
take advantage of the benefits that may be derived from the natural
communities on each site. While the use of existing vegetation for
low-energy landscaping may not be right for all sites, the concept
should be evaluated before construction activities begin.
Florida Division of Forestry. Tree Protection During Construction.
Florida Division of Forestry. Tree Protection Manual for Builders
and Developers. 1979.
Workman, Richard W. Growing Native. The Sanibel-Captiva Con-
servation Foundation, Inc. Sanibel, Florida 33957. 1980.
Bush, C. S. and J. F. Morton. Native Trees and Plants for Florida
Landscaping. (no date) Florida Division of Forestry.
Black, R.Landscaping to Conserve Energy. IFAS Fact Sheet EI-17.
F. A. Bartlett Tree Expert Company. Street Tree Study for the
District of Columbia. Stamford, Conn. 1968.
This publication was promulgated at a cost of $1,080.68, or
10.8 cents per copy, to inform Florida residents about choos-
ing existing native plants to leave in home landscapes that
contribute to low energy use. 9-10M-80
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLOR-
IDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES,
K. R. Tefertller, director, In cooperation with the United States
Department of Agriculture, publishes this information to further the
purpose of the May 8 and June 30, 1914 Acts of Congress; and Is
authorized to provide research, educational information and other
services only to Individuals and institutions that function without regard to race, color,
sex or national origin. Single copies of Extension publications (excluding 4-H and Youth
publications) are available free to Florida residents from County Extension Offices.
Information on bulk rates or copies for out-of-state purchasers Is available from C. M.
Hinton, Publications Distribution Center, IFAS Building 664, University of Florida,
Gainesvllle, Florida 32611. Before publicizing this publication, editors should contact
this address to determine availability.