Gardening: Sunscreen for Plants

It looks as if we are in for a dry and sunny season. Water issues aside, many established garden plants are simply not acclimated to increased solar radiation in addition to the stress of less moisture. There are some temporary, or even permanent, solutions to give them some relief.

There are some remarkably effective fabrics to help grow healthier, more productive, and better-looking plants. One of the newest on the scene is not really a woven fabric, but rather a thin layer of spun polyester. These floating row covers, as they are called, are also advertised as protection from insect pests. The fabric comes in one or two widths (6 feet is common) and in lengths from 20 feet to 250 feet.

This fabric is easily cut to fit a particular need, whether it is shading one prize rose or a long row of cabbages that need protection from the cabbage moth. They can just be laid gently over the tops of plants or draped over simple frames constructed from PVC pipe or other stakes. To keep out insect pests, be sure to secure the bottom edge with soil staples (U-shaped pieces of steel wire), old timber, or rocks. Sprinklers (and rain, should that arrive) will still filter through to water the garden, as will light and air. The lightest weight fabric transmits at least 90 percent of the sunlight striking them, providing a 10 percent shade factor. Heavier weight products are also sold, so consult the packaging for information. One potential drawback: Poly row covers will also keep out any insects that might pollinate the flowers and vegetables they cover.

More well-known, probably, is shade cloth. The sole purpose of this fabric is to cut down on the solar radiation reaching the ground. The choices for this particular cloth are pretty wide. They are rated to provide as little as 15 percent to as much as 80 percent shade. Usually, the fibers of the fabric are black, although green shade cloth is also fairly common. Lay it over a permanent structure, stretch it between posts on the southern side of a vulnerable young plant, or prop it up temporarily over a small patch of newly planted veggies. Even bird netting, with its more open mesh, will provide some shade, especially if it is doubled over.

Somewhat controversial is spraying sensitive plants with an antitranspirant such as the products Cloud Cover or Wilt Pruf. These can help in extreme cases. They don’t actually shade plants, but they form a thin, transparent layer of a polymer that reduces the water lost through transpiration (the process by which leaves release water through their stomata). They should be used carefully, if at all, and only according to directions on the product.

To cool and protect trunks of woody trees (and perhaps large shrubs), paint or spray on a coat of whitewash. There are products specifically formulated for this purpose, but a very dilute solution of white latex paint can do the trick, as well.

Container plants are a little easier to deal with. Simply move them to a shadier, cooler spot. Keeping plants a little cooler will help reduce their water requirements, so give a thought to some extra shade during hot, dry weather.