Few homeowners give their central air system consideration when landscaping. That’s really too bad, because the right plants, carefully situated in relation to the outdoor component of the air conditioner, can contribute in a positive way to the operation of your system. Not only can planting well-chosen plants in a strategic location improve efficiency, but a carefully thought-out landscaping scheme can also protect your system. Let’s look at a few of the ways trees and your HVAC system can work together.

How Shade Trees Contribute to Efficiency

You know that shade trees keep your home cooler, just as you feel cooler when you stand under a sheltering tree out of the hot sun. But you may not understand exactly how this works in a home’s interior.

It’s a fact that planting trees so their shading canopies deflect the sun will keep your home from heating up as much as homes without tree canopies do. The Environmental Protection Agency reports that a strategically planned landscape can reduce air conditioning expenses by anywhere from 15 to 50 percent.

But that’s not all trees do. In addition to blocking the sunlight from heating the roof, trees also create a cool aura around the home. Trees pull moisture from the ground, which transpires through the leaves, slowly evaporating and cooling the air around them. This mist-laden air is sometimes six degrees or so cooler than the air further away from the trees. As you can see, you can create something of a cool zone around your home by planting trees.

Some homeowners also plant smaller shade trees to shade the condenser (that’s the outdoor component of your air conditioner). While you don’t want leaf debris and twigs falling into the unit and impairing its performance, some shade will contribute modestly to keeping the condenser cooler as it works hard on hot days.

And don’t forget shrubbery. While you’ll likely keep them trimmed below the roof line, shrubs can help keep sun from penetrating the home through windows.

Choosing The Right Plant Material

It’s important that you choose the right kinds of trees and shrubs for your landscape. If you’re a novice in these matters, you can consult with horticultural professionals from the local extension office, a botanical garden or a good plant nursery about selections for your yard. Better yet, hire a landscaping professional to help you choose and situate your trees to best advantage.

Often, native plants are the best choice. They usually thrive better, with fewer disease and pest problems, than exotic species. Whenever possible, choose drought-tolerant species so that your water bill isn’t out of sight.

Speaking of water, you will have to water generously until your new plants are established, but generally, after a couple of years, you can cut back as the roots grow deeper and can find moisture in the water table.

Here are some points to consider as you select shade trees for your home.

  1. Avoid fast-growing trees such as silver maple, mulberry, chinaberry or members of the poplar family. While you’ll get shade faster with fast-growing trees, they are usually brittle and break easily. Silver maple and cottonwood also need a lot of water.
  2. Rule out trees that shed. You don’t want fibers such as that from cottonwoods clogging the condenser and preventing your air conditioner from exhausting warm air properly. You may also want to avoid trees such as mulberries that could drop fruit through the protective grating over the condenser.
  3. Avoid coniferous trees. Coniferous trees have leaves all year long; deciduous trees drop their leaves in the fall. You’ll want leaves gone so sunlight can reach the house in the winter when it’s colder.

It’s also important to think about how large the plants will grow. Most of us have made the mistake of underestimating the mature size of plants, in terms of how close we plant to the house or in proximity to each other.

Deciding Where Trees Or Shrubs Should Go

Once you’ve determined which trees and shrubs you want to use in your landscape, you’ll need to decide where to plant them. Here are a few key rules to adhere to:

  1. Don’t plant too close to the house or condenser. Trees planted next to a house can cause problems with the roof. If tree limbs start touching the roof, you’ll need to keep them trimmed back. Also, the roots of trees planted too close to the home may be a problem, undermining the home’s foundation or growing into the plumbing pipes and clogging them. A good rule of thumb is to maintain about 10 to 20 feet between the tree and the home’s exterior.
  2. Shrubs obviously can be closer to the house, but do plant them so you can get into the space between the shrubs and the home to trim them. You might want to avoid planting shrubs with thorns or prickly leaves against walls or around the condenser, as you will need to clean windows, and the HVAC tech will need access to the unit.
  3. When you plant shade for the condenser, make sure you allow for at least a 2-foot space between the shrubs and the unit. Plants shouldn’t interfere with airflow.

Miscellaneous Considerations

Garden structures.

Aside from plants, you should also create a plan for garden structures, such as walls, tool sheds, entertainment areas, furniture and the like. It’s always best, whenever possible, to locate these structures away from the HVAC system so as not to affect air flow. If you want to erect a structure to provide some shade to the condenser or to conceal it, you might consider a trellis or arbor, where you can grow vines or climbing roses. These plants will allow air flow while concealing the presence of the condenser in an attractive way.


If you’re into xeriscaping (the type of landscaping that uses minimal water or irrigation), you may have planned to eliminate grass and put down plastic weed barriers with gravel or pebbles on top of them. If you have these pebble- or stone-strewn landscape areas near the condenser, be sure to weed or cut any grass that grows there by hand. Using a weed whacker can propel pebbles into the condenser and may harm it.

Mowing grass.

If grass grows next to the condenser, it should be dispersed away from the condenser during mowing. Grass can clog the unit and affect air intake.


Adding trees and shrubs to your landscape in a pleasing, well-thought-out design is a great way to enhance your property values, while also boosting the efficiency of your home by making it cooler and more comfortable. Your air conditioner will also last longer since the parts won’t need to work so hard to reach temperature set points in the hot, hot summertime.

Furthermore, trees help reduce your carbon footprint, as large, mature trees actually help remove a significant amount of greenhouse gases: as leaves breathe, they draw the gases into the tree and deposit them into the ground through the roots.

So get going and start planting, and those trees and shrubs will be enhancing your comfort and efficiency before you know it.