• Topics: Environmental Horticulture  | Landscape Tree Selection -- South Florida  | Landscape Plant Selection -- South Florida  | Black, Robert J 

Landscape Trees for Energy Conservation--South Florida Trees¹

The use of landscape materials to moderate effects of adverse climates is not a new concept, but is receiving considerable attention in view of the current emphasis on energy conservation. Residential utility rates have escalated substantially to warrant adoption of any number of conservation measures. Collectively, measures such as skilled landscaping, increased insulation, solar hot water heaters, adjusted thermostat levels, and others can result in significant savings to the homeowner.

It has been estimated that the potential value of "low energy" landscapes can result in a 20-30% reduction in energy consumption. Presently, residential energy use in Florida accounts for 23% of the total energy budget. Investing in new plantings not only provides pleasure from an aesthetic sense, but will have direct benefits in reducing future energy consumption.

A major benefit of landscaping is to limit solar radiation on windows and exterior walls. In south Florida (see Figure 1) during the five-month period from mid-May to mid-September, temperatures exceed human comfort levels. Trees are the most effective form of plant material for limiting solar radiation. Proper placement should ensure maximum shading. Tree shade can be most effective on the surfaces of east and west sides of residences.

Figure 1. 

Florida regions.

The altitude of the sun is sufficiently high during summer months that solar loads on south-facing walls are minimal. When the sun is directly overhead, trees provide little benefit since most canopies do not extend over the roof. Roof insulation is generally adequate to prevent elevated internal temperatures. Deciduous trees can be used effectively in south Florida during winter months (November-February) when the warming effect of the sun can be beneficial.

Information presented in the tables in this publication should assist the homeowner and designer in selecting trees for south Florida. Trees have been classified and presented according to size, density of shade, rate of growth and whether they are evergreen or deciduous. General information has been included in the notes column on items such as surface roots and flowering character, among others.

• Table 1 . South Florida Trees--Small (Mature tree height shorter than 25 feet)

• Table 2 . South Florida Trees--Medium (Mature tree height 25-40 feet)

• Table 3 . South Florida Trees--Large (Mature tree height taller than 40 feet)

Three size classifications have been used: small less than 25 feet (7.5m), medium - 25-40 feet (7.5m 12.2m), and large - over 40 feet (12.2m). Small trees are best used as patio trees or they can be planted relatively close to the house to block morning and afternoon sun directly. Medium trees, because of their canopy and size, provide extensive shade on lawns and patios. They limit solar radiation by direct blocking or by casting shadows on wall surfaces. Generally, medium trees should be planted 10 to 15 feet (3-4.6m) away from the house. Large trees and those with wide spreading canopies should be restricted to the perimeters of most residential lots.

Tree form is quite variable and accordingly shade patterns vary with each form. The forms used are horizontal spreading, rounded, vase, pyramidal, and oval.

Maximum shading is provided by horizontal spreading forms, but unfortunately, not many small or medium trees exist in this form. Rounded or oval forms can be just as effective if multiple plantings are used. Pyramidal forms are least effective. Remember that the shadow of a broad tree with a low canopy moves much more slowly than the shadow of a tall, slender tree.

Density of tree canopies can have as much effect as tree form on solar reduction. Density of shade is related to the size of the foliage and the general compactness of the crown as influenced by branching habit, number of leaves, and internode length. Trees have been classified according to light, moderate, or heavy shading, but even these are approximations since cultural practices can have a major influence on the density of a tree's growth.

Growth rate and initial planting size will ultimately determine how quickly benefits will be derived from newly installed plantings. Generally, the largest affordable tree available to most homeowners is one with a stem caliper of 2-3 inches (5.0-7.6 cm), an overall height of 8-10 feet (2.4-3.0 m), and a spread of 3-4 feet (0.9-1.2 m). The lowest limbs are usually 3-4 feet (0.9-1.2 m) from the soil surface. A tree with a fast growth rate generally grows more than 3 feet (0.9 m) during one growing season, whereas trees with moderate growth rates grow from 2-3 feet each year (0.6-0.9 m) and slow-growing trees grow less than 2 feet (0.6 m) annually.

Every effort should be made to determine conditions present on your site with regard to light intensity, soil pH, soil drainage, and soil type. Your county agent or local nursery can assist you in selecting trees appropriate for your site conditions. Information contained in Fact Sheet ENH-22 "Ornamental Trees for South Florida," can provide additional cultural information on a number of trees listed in this publication.

Tables

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer, Interim Dean.

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