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Sheltering Your Greenery

2011-07-11
Pecan, mineral, and glass mulch

Plants can't move. Help them out with mulch and more

Over much of the nation, the sun seems intent on breaking all summer temperature records. Because plants can't sidle over to a shady spot, here are some helpful gardening tricks for covering up your tender greenery from Andrea DeLong-Amaya, the Wildflower Center's horticulture director.

  • Mulching: Covering the base of a tree or plant with a layer of mulch helps retain moisture in the soil and keep plant roots cooler during warm weather. From 2 to 4 inches of mulch is best over a plant's root zone (for trees, go out to the "drip line."). Leave a few inches bare right near a plant's stem or a tree's trunk. This "water well" prevents wet mulch from rotting greenery. Check to see that mulch you purchase has been harvested sustainably or consider something like pine needle mulch or pecan shell mulch, which is available in the south (the shells are treated to remove acidic chemicals called tannins).

    If your yard holds water too well, opt for "mineral" mulches such as pea gravel, decomposed granite or recycled glass. Their coarse composition allows moisture to drain away from the base of plants. A middle-of-the road option is pecan mulch, which has rough edges that shed water better than traditional organic mulches, but absorbs moisture as they do. To learn more about mulch options and its benefits.

  • Shade structures: If a plant's leaves lighten or you see brown, yellow or white areas on leaves in direct sun, it may have the equivalent of a sunburn. Consider using tomato cages covered with a material such as burlap or purchased shade cloth. Note that the more shade provided, the less air will pass through to the plant. To avoid creating a moisture trap that encourages fungal growth, create a roof or walls with the cloth rather than enclosing all plant surfaces (plants need sun exposure to make their own food through photosynthesis and to stay healthy). Shade structures help when you're starting new plants or transplants outdoors too, with the shading removed gradually over time.

  • Chemical cover-ups: If you're going on vacation or need added plant protection, check with local gardening centers about products that reduce plant moisture loss or protect them from ultraviolet light. Some are sprayed on the top of plant leaves and stems. The bottom of the leaves contain openings called stomata that can still shed water as part of a natural cooling process called evapotranspiration. Don't spray during full sunlight. Other products soak into the ground to be absorbed by the plant for a similar effect.

  • Potted plants can be moved into shade or the shadow of others. And remember that lighter pots will reflect more heat than darker ones, while clay pots absorb and lose more moisture than plastic ones (unless you use glazed clay pots).

And don't forget to ensure that plants have the right amount of water and nutrient-rich soil so they can grow shade-providing leaves. If you pull out all the stops and still lose some plants this summer, take stock of your garden layout. Review the lighting preferences of the plants that fared the worst to see if they received too much sun. Consider adding a trellis or planting a larger plant nearby for shade or moving the plant at a time when it can handle being transplanted. Relocation might be best fora struggling plant on a hill or in soil that retained moisture poorly. Are these plants locally adapted or native to your area? You could replace them with plants that have evolved to handle the weather in your region. To learn more about native plants appropriate for your area and their moisture, sunlight and other needs, visit: www.wildflower.org/explore.

By Barbra A. Rodriguez

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