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EES40 Enviroscaping to Conserve Energy: Trees for North Florida1 R.J. Black and A.W. Meerow2 1. This document is Circular EES-40, formerly Landscaping to Conserve Energy: Trees for North Florida, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: July 1993. Reviewed June 2004. Please visit the EDIS website at http://edis.ifas.ufl.edu 2. Robert J. Black, Extension Consumer Horticulturist; Department of Environmental Horticulture, Cooperative Extension Service; Alan W. Meerow, former associate professor, REC-Ft. Lauderdale, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611. The Florida Energy Extension Service receives funding from the Florida Energy Office, Department of Community Affairs and is operated by the University of Florida's Institute of Food and Agricultural Sciences through the Cooperative Extension Service. The information contained herein is the product of the Florida Energy Extension Service and does not necessarily reflect the views of the Florida Energy Office. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity Affirmative Action Employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Larry R. Arrington, Interim Dean Introduction Residential energy use comprises about 26% of all the energy used in the state of Florida (Florida Energy Office, 1992). In north Florida, almost 25% of this annual residential energy expenditure is for cooling the home during the 5to 7-month summer. And about 25% is used for heating in winter (Cook, 1993). As utility rates escalate, so does the cost of staying comfortable in the home. Glass windows and doors can account for between 30 and 60% of a building's total heat gain in the summer (Cook, 1986). As much as 270 Btu (a heat unit called British thermal unit) of direct and diffused solar radiation can enter a home or building through each square foot of glass on the east and west sides. For example, if sunlight strikes only 50 square feet of a clear glass window or a sliding glass door on a west wall, the cooling effect of more than one ton of air conditioning is required to remove the heat gained from this source alone. This is more than eight times the heat gain caused by conduction and infiltration. Even windows facing north or south can gain twice as much heat from indirect radiation as they gain from conduction and infiltration combined. Before central heating and air conditioning, homes were designed, built and landscaped to take advantage of natural cooling and heating. For example, a tree with high branches offers shade in the summer and insulation from cold winter winds. Today, passive methods of climate control are once again of interest because we are now aware of fossil-fuel supply limitations and the environmental effects of fossil-fuel use. New information has substantially improved many passive, energy-saving landscaping concepts (known as enviroscaping) from the past. Landscape plants can improve the appearance of our surroundings and modify the extremes of local climate (microclimate modification). Plants provide shade, insulate the home from heat loss or gain, and cool the air that surrounds their leaves through transpiration (release of water from leaf pores).
Enviroscaping to Conserve Energy: Trees for North Florida 2 Trees are the main type of landscape plants used around the home for passive energy conservation. They provide shade, influence air movement around the house and, once established, require little maintenance. The energy-conserving impact of a particular tree species depends on 1) whether it keeps its leaves during the winter and 2) the shape and density of its foliage. Planting Site Selection House walls are the most practical to shade because new tree plantings take many years to cast an effective shadow on the roof. Heat transmitted through the roof is best reduced by using attic insulation, radiant barriers and ventilation. This is because tree limbs over the roof can present both a nuisance (litter clogging rain gutters) and risk of damage or injury should heavy limbs fall off in a storm. Existing vegetation that can provide roof shade without undue risk, however, should be retained and incorporated into the homesite design. The correct placement of trees shading the home involves consideration of mature tree height, structure height, and the angle of the sun's rays in summer and winter. In general, the target areas for shading during Florida's warm months are the walls on western, eastern and southern exposures, in that order. Though an exposure facing due south receives little direct sun on June 21, by August the sun is low enough in the sky to increase heat loads considerably on south walls. Windows provide the most direct entry for heat into the home. Consequently, special attention may need to be given to walls containing the most windows. The benefits of new shade trees should be felt within 5 years. To accomplish this goal, a distance of 7 to 20 feet from tree to wall is recommended. Lot size and mature tree height directly influence this distance. The closer a tree is to the house, the longer its shading effects last during the day. The shadow of a tree planted 10 feet from the home moves across the shaded surface four times more slowly than a tree planted 20 feet away. If winter windbreak effects are desired, trees should be planted on the north and northwestern exposures of the home. This is the prevailing direction of blustery, winter winds in most of Florida (See EES-5 "Florida Climate Data"). The effects of summer breezes, which usually prevail from the southeast and southwest in Florida, are often desirable during mild, transitional times of the year. Where air conditioning exclusively cools the home for most of the hot season, summer winds can reduce cooling efficiency by increasing hot, humid air infiltration around window and door fittings or cracks in siding and masonry. In this case, a tree windbreak located on the southeast exposure of the house deflects the energy-robbing winds from the home. Tree Selection The chart at the end of this circular provides information that will help you choose one or more species best suited to your house and landscape. The trees are alphabetized by scientific name. The size category specifies the mature height of the tree (small, small-medium, medium, medium-large, and large). If shade requirements are immediate, give careful attention to the growth-rate designation in the chart. A fast-growing tree increases in height by 3 or more feet per year and provides shade benefits within 5 years. Most fast-growing trees, however, are both short lived and weak wooded, two undesirable characteristics. In such cases, it may be desirable to plant both a small, rapidly growing tree and a moderate or slow-growing species nearby. The fast-growing tree could then be removed once the other species provides shade benefits. Site conditions directly influence the establishment and life of a landscape tree. Coastal residents should heed the salt-tolerance ratings of the listed species. "General Comments" on the chart give specific tolerances (or intolerances) of a particular species. Tailor your choices to match the conditions on your site. For instance, a tree requiring well-drained soils does not prosper where standing water accumulates after a heavy rain. If this condition applies to your homesite, choose trees for wet-soil tolerance as indicated (e.g., red maple, Acer rubrum; sweetbay, Magnolia virginiana; and loblolly bay, Gordonia lasianthus).
Enviroscaping to Conserve Energy: Trees for North Florida 3 Relative drought tolerance is also indicated for each species. These ratings refer to Florida conditions only and should be interpreted as follows: High survives without supplemental irrigation after establishment; Moderate requires supplemental irrigation during very dry periods to maintain satisfactory appearance and health; and Low little or no drought tolerance. Drought tolerance also varies with soil and other environmental conditions. Whether a tree is evergreen or deciduous ("Leaf Persistence" on the chart) affects its performance. Deciduous trees, which drop their leaves in winter, are recommended for use on south, southeast and southwest exposures. In summer, they provide desired shade. In winter, their bare canopy allows the sun's rays to warm the home, creating additional energy savings. On the other hand, evergreen trees, which have leaves all year, on the north and northwest exposures provide the most effective barrier to cold, winter winds. The shape of a tree influences how long shade lasts. Spreading, round and vase-shaped canopies provide the longest periods of shade during the day. With attention to both this category and the shade-density rating, home-shading needs can be fine tuned to meet individual needs and desires. Interest in native plant materials has increased greatly in the state, so all native species are marked with an asterisk (*) on the chart. In some cases, native plants may be better adapted than exotic species to local soil and weather conditions. Planting and Maintenance All new tree plantings benefit from soil preparation, regular irrigation, and, in some cases, protection from insects, disease, or weather extremes. Young trees require a period of regular aftercare to ensure proper establishment. Knowledgeable nursery employees and county extension agents are good sources of answers to individual problems. Detailed information on proper tree placement, shading patterns, and microclimate modification are in the following publications available at your county extension office: EES 43 "Enviroscaping to Conserve Energy: Microclimate Modification" EES 49 "Enviroscaping to Conserve Energy: Determining Shade Patterns for North Florida" EES 50 "Enviroscaping to Conserve Energy: Determining Shade Patterns for Central Florida" EES 48 "Enviroscaping to Conserve Energy: Determining Shade Patterns for South Florida" References Cook, Gary. 1986. "A Guide to Selecting Window and Glazing Options for Florida Buildings." IFAS/Florida Energy Extension Service EES-36. Gainesville, FL. Cook, Gary. 1993. Personal communication. Gainesville, FL. Florida Energy Office. 1992. Florida energy data report: 1970-1990. Dept. of Community Affairs, Florida Energy Office, Tallahassee, FL. Key to North Florida Trees See the following chart for keys to north Florida trees. Leaf Persistence: D = Deciduous, E = Evergreen, S = Semi-Evergreen Form: C = Columnar, O = Oval, P = Pyramidal, R = Round, S = Spreading, V = Vase-Shaped Growth Rate: S = Slow, M = Moderate, F = Fast Shade Density: L = Light, M = Medium, H = Heavy Size: S = Small (up to 25 feet), M = Medium (25 40 feet), L = Large (more than 40 feet) Drought Toler.: L = Low, M = Moderate, H = High Salt Tolerance: N = None, L = Low, M = Moderate, H = High
Enviroscaping to Conserve Energy: Trees for North Florida 4 Table 1. Tree selection for north Florida. Scientific Name Common Name = native Leaf Persistence Form Growth Rate Shade Density Size Drought Tol. Salt Tol. General Comments *Acer negundo Box elder D S F M L M N Many cultivars. Low branching. Subject to aphids. *Acer rubrum Red maple D S F M M-L L L Tolerates wet soils. Red flowers. Fruits in late winter/early spring. *Acer saccharum / A. barbatum Sugar maple / Florida maple D O F M M-L M N Dead leaves hang on through the winter. *Betula nigra River birch D O F M L L N Attractive bark. Tolerates wet soils. Few pests. *Carpinus caroliniana American hornbeam D R S M M L N Interesting "sinewy" limb shape. Tolerates wet soils. *Carya glabra Pignut hickory D O S M L H N Subject to bag worms. Nut crop may cause objectionable litter. Carya illinoensis Pecan D O S M L M N Moist, fertile soil. Two varieties needed to set good pecan crop. *Celtis laevigata Hackberry / Sugarberry D R M M L H N Prefers moist soils. Tolerant of urban conditions. *Cercis canadensis Redbud D R M M S-M M N Showy, early spring flower display. Attractive foliage. *Chionanthus virginicus Fringe tree D R S M S L N Prefers rich soil; airy spring flowers in mass display before leaves emerge. *Cornus florida Dogwood D R M M S M L Beautiful spring flowers. Red fruits and fall color. Attractive tiered branching pattern. *Crataegus spp. Hawthorn D V M L S H N Irregular shape. Thorny branches. Spring flowers; fruits in late summer to fall. Eriobotrya deflexa Bronze loquat E R M H S H M New growth attractive bronze or red color. Eriobotrya japonica Loquat E R F H S H M Fragrant flowers in the fall. Edible fruit. Tolerant of most soils. Host of Caribbean fruit fly. *Fraxinus pennsylvanica Green ash D R F M L M N Fruitless cultivars available. Ginkgo biloba Maidenhair tree D V S M L M N Separate sexes. Female trees' fruit has foul smell. Several cultivars. Tolerates poor conditions.
Enviroscaping to Conserve Energy: Trees for North Florida 5 Table 1. Tree selection for north Florida. Scientific Name Common Name = native Leaf Persistence Form Growth Rate Shade Density Size Drought Tol. Salt Tol. General Comments *Gordonia lasianthus Loblolly bay E O M M M L N Fragrant, white flowers from summer to fall. Tolerates wet soils. *Halesia diptera Silver-bell D R F M S L N Dainty white flowers in spring. Best in partial shade. *Ilex cassine Dahoon E O M L M M M Salt tolerant. Best in moist soils. Attractive red fruits on female plants. Ilex latifolia Luster-leaf holly E P M H M M N Difficult to propagate. Generally pest free. *Ilex opaca American holly E P S M M-L H L Attractive foliage. Red berries on female plants. Ilex rotunda Round holly E R S H M M N Attractive specimen tree. Several cultivars. *Juniperus silicicola Southern red cedar E P S M M H H Salt tolerant. Tolerates neglect. Difficult to transplant. Good windbreak species. Juniperus virginiana Eastern red cedar E C M M M-L H M Tolerant of salt and poor soil. Good windbreak tree. Lagerstroemia indica Crape myrtle D V M L S H N Many cultivars with different flower colors, size or habit. Flowers for long period in summer. Ligustrum japonicum Japanese privet E V F M S M L High salt tolerance. More commonly used as shrub. *Liquidambar styraciflua Sweet gum D R F M L H N Fall color. Spiny fruit a problem in some situations. *Liriodendron tulipifera Tulip tree D O F M L L N Few pests. Very straight trunk. Needs space. *Magnolia grandiflora Southern magnolia E O S H L H M Long-lived. Salt tolerant. Fallen leaves do not readily decompose. Large, fragrant white flowers. *Magnolia virginiana Sweetbay E S M M M-L L N Attractive, silvery leaf color. Tolerates wet soils. Magnolia X soulangiana Saucer magnolia D R S M S M N Outstanding spring flower display. Prefers fertile soil and good care. *Malus angustifolia Crab apple D V F L S M N Spring flowers. Prefers fertile soil.
Enviroscaping to Conserve Energy: Trees for North Florida 6 Table 1. Tree selection for north Florida. Scientific Name Common Name = native Leaf Persistence Form Growth Rate Shade Density Size Drought Tol. Salt Tol. General Comments *Morus rubra Red mulberry D S F M M M N Messy in fruit, but fruitless cultivars available. *Myrica cerifera Wax myrtle E R M M S H H Tolerates salt and unfavorable soils. Aromatic foliage. *Nyssa sylvatica Tupelo / Sour gum D O M M L L N Tolerates wet soils. Good foliage with fall color. *Ostrya virginiana American hophornbeam D O M M M M N Pleasing, irregular branching pattern. Tolerates dry soils. Parkinsonia aculeata Jerusalem thorn D S F L S H L Unusual green branches and picturesque form. Good late spring flower show. Very drought tolerant. Thorny. *Pinus clausa Sand pine E O F L M H L Persistent cones. Picturesque leaning or twisted habit when old. Very tolerant of poor, dry soils. *Pinus elliottii Slash pine E R F L L H M Straight trunk. *Pinus glabra Spruce pine E O M L M H L Tolerates moist sites. Attractive form and texture. *Pinus palustris Longleaf pine E R M L L H N Excellent background plant. Straight trunk, long needles. *Pinus taeda Loblolly pine E R M L L H N Irregular crown. Good screen or windbreak. Pistacia chinensis Chinese pistache D O F H M-L M N Drought and heat tolerant. Fruit can be messy. *Platanus occidentalis Sycamore D R F M L L M Attractive exfoliating bark. Prefers moist, fertile soil. Platycladus / Thuja orientalis Oriental arborvitae E C M H S-M M N Good windbreak tree. Many cultivars. Tolerant of most conditions except salt. Podocarpus macrophyllus Podocarpus E C M H S-M M M Low branching. *Prunus angustifolia Chickasaw plum D R M M S M N Spring flower display. Fruit edible, but variable in quality. *Prunus caroliniana Cherry laurel E R F H S-M M N Low maintenance. Tolerates most soils. Fruit attract birds. Will naturalize.
Enviroscaping to Conserve Energy: Trees for North Florida 7 Table 1. Tree selection for north Florida. Scientific Name Common Name = native Leaf Persistence Form Growth Rate Shade Density Size Drought Tol. Salt Tol. General Comments *Prunus umbellata Flatwoods plum D R M M S M N Spring flower display. Fruit edible, but variable in quality. Pyrus calleryana Bradford pear D R M M S-M M N Fireblight resistant. Spring flowers. Fall color. *Quercus falcata Southern red oak D R M M L H N Tolerates dry soil. *Quercus laevis Turkey oak D O M L M-L H N Short-lived. Can be difficult in cultivation. Best in native landscape. *Quercus laurifolia Laurel oak S O F H L H L Height greater than spread. Lives only 30-50 years. *Quercus nigra Water oak S V F H L H L Short-lived (20-30 years). Tolerates moist soils. *Quercus shumardii Shumard oak D R M M L H N Handsome form. Good fall color. *Quercus virginiana Live oak S S M H L H H Old trees very picturesque. Spread greater than height. Long-lived. Salt tolerant. Salix babylonica Weeping willow D S F H L L N Generally lives for only 20-30 years. *Sapindus saponaria Soapberry D R M M M H M Soap-like compound prepared from fruit. Fruit can be messy. *Styrax grandifolia Styrax D R M M S L N Attractive spring flowers. *Taxodium distichum Bald cypress D P M L L H N No serious pests. Very tolerant of both wet or dry soils. *Ulmus alata Winged elm D R M M M H N Interesting, corky branches. Ulmus parvifolia Chinese elm D S F M M-L H M Tolerates dry soils and salt. Very attractive, exfoliating bark. Ulmus pumila Siberian elm D R F M S M M Short-lived. Several cultivars. Viburnum odoratissimum Sweet viburnum E R F H S M N Very fragrant flowers in spring. X Cupressocyparis leylandii Leyland cypress E P F H M-L M L Several cultivars differing in size, shape, and foliage color.