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Plant Answer Line Question

Keywords: Water-absorbing polymers, Container gardening

I am doing container plantings for clients (some of them big -- the containers, not the clients), and have water concerns. Have you received any feedback on use of those "soil moist" granules that are supposed to cut down on waterings? My fear is that over time, especially with shrubs in a container, there may be some root rot.


Although there is not any conclusive information on whether use of water-absorbing polymers will contribute to root rot in planters, there are quite a few other causes for concern. Local gardener and writer Jessica Salmonson discusses the matter on her web site, Paghat's Garden.
Here is a brief excerpt:

Many of the 'superabsorbent' properties claimed by polymer manufacturers are exaggerated, and during biodegradation these polymers even reverse their effect, depriving plants of moisture. Woodchips, quality compost, or peat do the same job adequately, plus the woodchips or compost provide safe plant nutrients and a medium for beneficial microorganisms such as polymers retard.

And, inevitably, it turns out that some polymers do in fact reach the foodchain, especially the allegedly safer-to-the-environment biodegradable synthetic polymers. These are fed directly to livestock as feed supplements, are dispersed over crops in herbicides & pesticides, & are mixed into garden soils because of preposterous claims of doing away with a need ever again to water the garden.

Extension horticulturist and Washington State University Professor Linda Chalker-Scott has also written on this issue, and states that even beyond the health and environmental concerns, hydrogels do not work well in clay soils, and can decrease a plant's ability to absorb essential nutrients.

Local garden writer Ann Lovejoy writes about a non-polymer alternative in this article in the Seattle Post Intelligencer: "The newest such water holder I've tried is called Quench. This is a granular, sand-colored material that turns cloudy-translucent in water. Unlike polymers, Quench is based on a natural material (cornstarch) in a form that can absorb up to 400 times its weight in water, right up there with good compost or forest duff. Unlike the usual polymers, this stuff lets go with grace. About 95 percent of the stored water is released to plant roots in midsummer, making plants a lot less dependent on people in hot weather."

Date 2017-05-17
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May 31 2018 13:14:08