An Idea That Just Might Hold Water : Consumers: Polymers may prove to be lifesavers for drought-threatened gardens. When mixed with water, they swell up and retain moisture near a plant’s roots.
Trying to save water and still preserve your plants and yard? Tiny white crystals that look like rock salt, but that can absorb up to 40 times their weight in water, might help.
The synthetic crystals, called polymers, are selling fast in garden stores and nurseries, and at least one tree service is field-testing them in California.
“A lot of researchers are looking at polymers. We’re still doing field trials here at our lab farm,” says Roger Funk, plant physiologist and polymer researcher at Davey Tree’s national headquarters in Canton, Ohio.
“Theoretically, they do work. They do hold water, but we can’t necessarily substantiate the claims of the manufacturers yet,” he says of Davey’s three years of testing. “But we felt the situation is critical enough (in California) that we should do field trials there.”
Polymers are mixed with fertilizer and, when combined with water, swell up like a gel to retain the water near the shrub or tree roots.
Funk says polymers didn’t work when Davey researchers first tried them five or six years ago. Those polymers were natural starch derivatives and lasted only two months to a year at most, he says. The newer polymers are poly acrylamide synthetics and will last from two to four years in soil.
“They absorb water, and in doing that, swell up just like Jell-O and hold water against the pull of gravity,” Funk says.
Most garden centers sell nontoxic polymers that can be placed around plants, shrubs and trees--indoors and out. They cost from $13 to $17 for a one-pound box and should be used with water-soluble fertilizers.
A one-pound box of Agrosoke, a Texas-manufactured polymer, will treat 100 square feet of soil, according to Joseph Ward, manager of Armstrong Garden Center in North Hollywood. Ward says he recommends Agrosoke because, unlike other polymers, it does not pull water from the plant. Agrosoke manufacturers say their product, which absorbs up to 40 times its weight in water, allows the roots to attach to, and take water from, the crystals.
“People are concerned and they’re trying to do something,” says Ward. “We’ve sold so much of the polymers within the last two months. I wouldn’t put in a brand new lawn, either seed or sod, without polymers. The initial expense will be more, but the lawn should do better. (It) can reduce watering by as much as 50% and it lasts for years.”
Davey Tree’s polymer treatment averages about $50 a tree in Southern California, depending on the number of trees and their size. The firm injects the soil around the roots with a solution of polymers and fertilizer.
If you don’t want to try polymers, cheaper alternatives are available. Regular fertilizing can help trees, shrubs, lawns and plants maintain a strong root structure, and mulching helps plants hold in water.
Plastic sheeting or weed mats around plants and shrubs also helps retain moisture and, when covered with bark, offers even more protection. Plastic sheeting costs about $8 for a 10-foot roll, 25 inches wide; three-foot-wide weed mat costs about 35 cents a foot.
Ward cautions, however, about which plants should be treated: “Don’t use polymers or plastics with cactus, or you’ll end up with problems. Drought-tolerant plants don’t need polymers.”
