Don’t encourage termites: 7 smart gardening practices
By Dan Gill, The Times-Picayune garden columnist
The next several months are a popular time for adding or reworking beds of shrubs, ground covers, and flowers next to your house. As you do so, remember, this work can affect your home’s termite protection.
We often refer to beds located close to the house as “foundation plantings” or “foundation beds” (so named because they are meant to hide the foundation of the home). Beds out in the landscape away from the house are not an issue. But, when landscaping foundation beds, the LSU AgCenter provides a variety of recommendations to avoid affecting your termite protection.
Many houses are protected from subterranean termite damage with chemical barrier-type soil treatments. Native subterranean termites always enter a home through the soil right next to a slab, pier or attached structure. The introduced Formosan termites generally do as well, but there are some exceptions (see later in the column).
To protect the structure, the soil immediately next to the slab or piers is treated with a long-lasting liquid termiticide. Piers also are drilled, and the termiticide injected into the inner void, and termiticides are applied under the slabs of houses during construction. The treated soil next to the slab or piers typically is about 4 inches wide and about 6 inches deep. The presence of this chemical forms a protective shield that prevents termites from tunneling through the soil and entering the structure.
The soil in this area should be considered untouchable. It’s all that stands between your house and an infestation of termites. If anything is done to this soil, the barrier is compromised, and the risk of termites entering the structure is increased.
During bed preparation for foundation plantings, it’s imperative not to dig into the soil at least 8 to 12 inches out from the slab or piers. If new soil is being added to the bed, it should not be allowed to cover the soil within 8 to 12 inches of the slab or piers. Either of these actions reduces or eliminates the effective barrier.
When planting shrubs in beds next to the house, they should be located a minimum of 3 feet from the slab. This distance allows for growth of the shrubs over time. The shrubs will benefit from better light and air circulation that the space behind them provides.
It also keeps them from coming into contact with the house. Woody plants touching a structure may provide a route of entry for subterranean termites. Vines also should not be allowed to grow on your house.
Structures should be inspected for signs of subterranean termites at least once a year. If plants are close to the residence, it may be difficult to get behind them to inspect the slab or piers. This is particularly true of plants with thorns or spines.
I encourage gardeners to use mulches in beds of shrubs, flowers, establishing ground covers and vegetables. They provide numerous benefits. But, when mulches are applied to beds adjacent to your house and other structures, termite prevention needs to be considered.
I often get questions about mulches attracting termites to a house. This is not the case, although termites will feed on the cellulose that makes up plant-based mulches. The mulches most likely to be fed upon by termites are wood products, such as wood chips. Some woods have natural chemicals that make them less palatable to termites (such as redwood, eucalyptus, and cedar), but these chemicals break down, leach out and don’t last indefinitely.
Wood mulches should not be used in beds next to the house. Bark-based mulches are less favorable, but still may be eaten.
Pine straw is the most commonly used mulch that is lowest in cellulose and is a good choice for foundation plantings. Mulches that are not plant-based, such as rubber mulches, gravel, and rocks, are, of course, not in the termites’ diet.
The placement of the mulch is more important than what you use. You should never apply mulch right up to the slab or piers of a house. This forms a bridge over the chemical soil treatment allowing the termites to bypass the barrier and enter the home. Keep mulches pulled back 8 to 12 inches to prevent this from happening. Mulches are not needed close to the structure if beds are planted the proper distance from the house.
Large trees near a house can clog gutters with large amounts of leaves. (Live oaks are shedding leaves now.) Clogged gutters overflow when it rains, wetting the wood of the fascia and roof of the house. Leaky gutters do the same thing.
Although native subterranean termites must enter the house from the soil, Formosan subterranean termites just need damp wood. So, if wood in your roof area stays damp, a colony can get started directly in that location — bypassing the soil barrier.
When possible, plant larger trees farther from your house and prune branches to minimize leaves in gutters. Keep your gutter clear of leaves and in good repair.
More Tips to Minimize Termites
The following tips come from the LSU AgCenter.
Place gutters and grade your landscape so water drains away from your house.
Do not add fill dirt around the foundation or under porches or steps without contacting your termite company for re-treatment.
Promptly remove all scrap wood and wooden debris from the landscape.
Use metal edging, decorative bricks or border plants to edge your beds. Avoid wooden materials that may serve as food for termites.
When watering, avoid frequently spraying water against the foundation of your house. Adjust sprinklers so that they do not wet the sides of your house.
Leave at least 2 inches of space between your house and a deck or other wooden structures outside. Wooden trellises with plants trained on them should be at least 6 to 8 inches away.
Build decks and other structures on concrete pads and treat around the pads and posts. Treat under pads, too, and use pressure-treated wood in outdoor settings.
Dan Gill is a horticulturist with the LSU AgCenter. Email questions to firstname.lastname@example.org or add them to the comment section below. Follow his stories at www.nola.com/homegarden, on Facebook and @nolahomegardenon Instagram.
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