University of Florida

Enviroscaping


Shade trees and groundcovers can reduce cooling costs and make your home more environmentally friendly.

Introduction

Historically, landscaping has played an important role in modifying the home environment. Until the invention of mechanical heating and cooling systems, humans had to depend on their ability to change or modify their surroundings.

To encourage air flow in Florida's moist, hot climate, people designed open homes and used trees and other landscape materials to channel tropical winds. These cooling coastal breezes offered a welcome relief from uncomfortably warm temperatures.

Florida Climate

Sunlight

Florida's consistently warm temperatures--generated by sunlight--can be a mixed blessing. Between April and November, sunlight intensities can elevate air temperatures far above the human comfort zone.

Humidity

Being a peninsular state, Florida is exposed to moist ocean breezes. Tropical air sweeping off the Gulf of Mexico is heated by the sun, resulting in a hot, humid climate. Florida also receives an average of fifty-four inches of rain per year, increasing the already-high humidity levels. This moisture-laden air fluctuates little in temperature, with the annual average between 67°F and 78°F. For Florida's permanent residents, living comfortably in this tropical climate can be challenging.

Winds

For much of the year and across most of Florida, winds provide natural ventilation. Coastal areas can depend on daily breezes for relief, but inland areas must rely on other factors to direct and enhance modest wind flow.

Getting Started

Florida offers an enticing atmosphere without the wide temperature fluctuations or arid conditions that trouble many other states. From the hilly regions in the North to the tropical Keys, Florida provides many unique opportunities for using landscape materials to control the home environment, creating a more comfortable home environment and reducing utility bills.

In response to intense Florida temperatures, residents continually look for ways to keep out the heat and lower inside humidity. Numerous effective planting methods will limit the amount of heat or moisture that enters your home. Trees, shrubs, grasses and other groundcovers can be highly effective in controlling these elements when combined with planting strategies specific to Florida's hot humid climate.

As a homeowner, you should begin by making a list of specific problems you would like to correct. Ask yourself the following questions so that your landscape design can be tailored to meet your specific needs.

  • Does your house have particular windows that need to be shaded?
  • Is humidity a problem on one side of your home? Encouraging wind movement could make that area of your yard more usable.
  • Is your home passively cooled (no air conditioning)? Houses that are passively cooled will require different landscape techniques than a home that uses air conditioning.

While you can't actually control the weather, you can channel winds, cast shade, and reduce moisture near our homes. Modifying these forces creates more comfortable living conditions and can lower your utility costs as much as thirty percent.

Using Shade to Reduce Temperatures

Research indicates that shade has a dramatic effect on ground temperatures. When shaded, ground temperatures were found to drop an average of 3 - 6°F in only five minutes. Studies have also shown that temperatures on a forest floor can be as much as 25°F cooler than those recorded at the tree tops.

Home comfort levels and energy costs can be also dramatically affected by shade. Creative landscape planning with trees, shrubs and vines will help alter the climate outside your home and modify indoor temperatures.

Trees

Determine the best places to plant shade trees by observing which of your windows receive the most sun. Your top priority should be providing shade for east and west windows and walls, since these surfaces receive about fifty percent more sunshine during the warmer months than those facing north and south.

When planning your design, keep in mind that trees are more effective at shading when planted close to the home. A tree planted ten feet from the west wall will shade an area four times longer than a tree planted twenty feet. A tree's shape also influences the duration of the shade. Spreading, round, and vase-shaped tree canopies will provide shade for the longest time.

Mature tree height should also be considered when selecting plants. In general, small- or medium-sized trees (26 - 30 feet) are preferred for shading sidewalls. Taller trees should be planted farther away from the home because they can become a safety hazard when canopies begin to overhang the roof.

During the summer months, deciduous trees have a full canopy of leaves that provide shade. In the winter months, they drop their leaves, allowing the warming effect of the sun to filter through. In general, the south and southeast sides of your home are the best locations for deciduous vines, shrubs and trees. Northern Florida is known to have winters with temperatures well below freezing, and having deciduous plants near you house can reduce how much you'll need to run the heater.

Shrubs & Vines

Shrubs are also useful for shading your home. When planted a few feet away from the house, they can provide extra shade and control humidity without obstructing air currents. Trellised vines can be used to shade windows where space is limited, since they can grow in more confined spaces than trees or shrubs. Evergreen vines are a good choice for providing shade along the east and west sides of the house. To take advantage of the winter sun, deciduous vines--such as wisteria--should be planted on southern exposures.

Air Conditioning Units

To keep air conditioning costs to a minimum, shade the outside condensing unit. Be careful to allow sufficient room for air to move around the condenser so that it can operate at peak efficiency.

Channeling Wind to Your Advantage

Wind channeling is perhaps the most talked-about but least understood landscaping technique for saving energy. Using landscaping to manage breezes is a very effective means of controlling indoor home temperatures during both winter and summer. By using trees, shrubs, vines, and other vegetation, you can alter the direction of wind near your home.

Mechanically cooled homes need windbreaks to the south to control summer breezes, keeping utility costs low. In contrast, passively cooled houses should be landscaped to direct breezes into the home.

Passively Cooled Homes

Cooling breezes are a precious commodity for Florida's passively cooled homes. Houses that use minimal or no air conditioning should concentrate on directing breezes toward windows and screened doors. To use these winds effectively, allow for cross ventilation. Operable windows should be positioned opposite each other on the north and south walls.

Make sure to place shade plants far enough away from the house so that they do not restrict air flow. Because they interfere with wind motion, avoid using low-branching trees (or remove the low branches) on the southeastern and or southwestern exposures.

Winter wind barriers on the north and northwest sides of the home can help push breezes from the south back toward the house during the summer. Shrubs placed near the windows can also be effective in directing air into the house. Full evergreens with low branches provide the greatest protection from the chilling northern winds common to north Florida winters.

Homes Designed for Mechanical Cooling

During Florida's long, hot summers, most residents find it impossible to stay cool without air conditioning. In order to keep your air conditioning costs to a minimum, consider outside air infiltration. Steady wind movement around the home during warm weather may actually increase your energy costs by allowing warm, humid air into your home. This air enters around windows, doors and through any structural cracks. Plants can be used to slow and redirect wind movement, helping you to keep your home cooler while you save energy.

Position shrubs and trees around your air conditioned home to steer the summer southern breezes away from the home. You can also use shrubs to slow wind movement and reduce the amount of warm air entering the home. The more dense and closed a shrub is, the more the wind is slowed. To determine where you should place vegetation on your lot, observe a wind sock or another similar device over a period of several days in winter and in summer. Once prevailing winds are determined, landscape planning will be a breeze.

Cooling with Groundcovers

Heat waves rippling over a sunbaked parking lot is a familiar sight during the summer. Paved surfaces absorb the sun's heat and radiate it back into the immediate environment. Research has shown that temperatures may be 15°F to 25°F hotter over asphalt or concrete. Paved areas also store heat, radiating warmth long after sundown. Paved surfaces around the home can contribute substantially to summertime heat loads. Planting groundcovers around paved areas can help reduce these temperatures.

Groundcovers are low-growing plants that can be used to cover an area in the landscape. Turfgrass is undoubtedly the most commonly used groundcover. No other plant material can withstand as much foot traffic as turfgrass. While turf makes an excellent choice for recreational areas, it does not grow well in dense shade and is difficult to establish in extremely wet or dry areas. Evidence indicates that taller groundcovers--with their larger leaf surface--can provide even more cooling than shorter groundcovers such as mowed grass.

There are several alternative groundcovers that adapt well to conditions unsuitable for turf. Lily turf (Liriope muscari) and mondo grass (Ophiopogon japonicus) are low maintenance groundcovers that tolerate dense shade. If damp soils are a problem, try planting day lillies. For seaside plantings, consider beach sunflower, which is both highly salt- and drought-tolerant.

All plants are capable of modifying their environment through a process called evaporative cooling. Plants release water through pores in their leaves. When warm winds pass over the leaf surface, surface water absorbs the heat. The warmed water then evaporates into the atmosphere, leaving behind a cooler environment. The resulting lower air temperatures around the home will reduce air conditioning costs.

In addition to saving time and energy, groundcovers can provide a more beautiful and comfortable home environment. Through a profusion of color and texture, groundcovers create interesting contrasts and provide an unifying element in a total landscape planting.

Low-energy Landscape Practices

Most residents delight in compliment their homes with a lush landscape bordered by a carpet of green lawn. In the process of creating an attractive home landscape, homeowners often overuse fertilizers, pesticides, and water, resulting in accelerated plant growth and requiring more frequent pruning, mowing, and general cleanup.

Fertilizers & Pesticides

A healthy, attractive landscape can be created without causing excessive plant growth or requiring extensive pest control. To achieve a good quality landscape, you must follow a planned maintenance program. Moderate applications of fertilizer can improve the appearance and condition of plants, making them more resistant to diseases and insects. Excessive fertilization requires more human effort, contributes to ground water contamination, and wastes valuable energy.

Besides the potential for ground water pollution associated with some pesticides, the manufacturing process requires large amounts of energy. Increased environmental awareness has caused many pesticides users to look for safer and more energy-efficient ways to manage disease and pests in the landscape. Moderate fertilizer and watering practices can help reduce the need for frequent pesticide use.

Water & Irrigation

A plant's growth rate is also affected by the amount of water it receives. Excessive watering--coupled with high fertilization rates--results in a rapid flush of growth and contributes to insect and disease problems. With Florida's limited potable water and mandatory water restrictions, you should implement sensible irrigation practices. Consider using micro-irrigation and drought-tolerant plant varieties wherever possible.

Yard Waste

You can conserve energy by carefully planning your landscape maintenance practices. Grass clippings are a valuable energy resource that many homeowners are throwing away. When mowing the lawn, simply let your grass clippings remain on the grass and allow them to decompose. Your lawn will recycle the clippings naturally, saving you time, money, and energy.

Each bag of grass clippings contains as much as one-fourth of a pound of organic nitrogen. Nitrogen is necessary to ensure healthy, attractive landscape plants. By using this free nitrogen, you can decrease your fertilizer needs, saving the energy required to produce these products.

Filling plastic bags with grass clippings and other yard debris is hard work and wastes valuable space at landfills. When you leave clippings on the lawn, you will reduce these negative effects and recycle important nutrients for free. Get in the habit of leaving your grass clippings where they fall. You will be rewarded with a green healthy lawn and more leisure time to enjoy it.

Recycling yard wastes conserves energy. Disposing of leaves, grass clippings, and other garden refuse is often a problem for gardeners, particularly in an urban area. Garden and landscape byproducts can easily be turned into useful compost. Returning these organic materials to the land perpetuates the natural biological cycle.

Adapted from:

Enviroscaping (EES101)--(pdf) by Joan Bradshaw and Linda Tozer. Published by: Environmental Horticulture Department (rev. 10/2003).

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