water absorbing crystals for plants

Do those water-absorbing crystals keep potted plants damp? Gardening Q&A with George Weigel

SoilMoist is one of the best-known brand of hydrogels.

Q: You mentioned in an article once about using polymer crystals as a way to help with keeping potted plants watered. I’ve never tried them. Do they really do much good? Are they worth the price? They seem kind of expensive.

A: This is one of those products that seems like it should work pretty well but only ends up making a marginal difference – at best. And some of them pose potential safety problems, according to one university horticulturist.

Polymer crystals are also known as “hydrogels,” and they’re clear or white dry crystals about the size of coarse salt grains that get worked into potting mix before planting.

They can absorb and hold up to 600 times their weight in water and then return it to the soil when it goes dry.

Hydrogels are marketed as ideal for helping to get pots through a dry spell, such as when you go away and miss a day or two or three of watering.

They’re sold under such brands as Soil Moist, Terra-Sorb, Miracle-Gro Water-Storing Crystals and Hydrosorb.

Dr. Jeff Gillman, author of “The Truth About Garden Remedies” (Timber Press, 2008), tested five brands of hydrogels while working as a researcher at the University of Minnesota. He concluded that none of them kept plants supplied with moisture any longer than soil without anything added.

Other studies have found similar results or only marginal gains in water-aiding.

“In most cases, hydrogels just don’t work very well,” Gillman writes in his “Garden Remedies” book. “While these products have shown themselves somewhat useful in some tests, they haven’t proven themselves on a consistent basis, and when they have reduced watering frequency, they haven’t reduced it by much.”

I’m more concerned by a warning from Dr. Linda Chalker-Scott, an associate horticulture professor at Washington State University and author of “The Informed Gardener” (University of Washington Press, 2008).

She says that most hydrogels are made of polyacrylamides, which break down into acrylamides, a known human neurotoxin and carcinogen. Because it’s unknown how long that stage persists or what effect it may have on health and water supplies, she recommends against them. (She adds that the occasional hydrogel user is probably not at much risk.)

If you’re at all concerned, manufacturers have begun making hydrogels out of starch instead of polyacrylamides.

I agree the crystals are expensive. You don’t need much (too much causes pots to bubble up and overflow as the crystals swell), but at $8 for a 3-ounce pack and $40 for a 3-pound canister, that seems like a lot of money for little or maybe no benefit.

You’ll get more return for your money by topping the potting soil with an inch of mulch, by lining the insides of the pot or basket with plastic (but not the bottom), and by using thicker-walled pots instead of fast-drying terra-cotta.

Or spend that $40 on a drip-irrigation pot-watering setup with an automatic timer to keep things moist when you forget or go away.

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Do those water-absorbing crystals keep potted plants damp? Gardening Q&A with George Weigel SoilMoist is one of the best-known brand of hydrogels. Q: You mentioned in an article once about

What Are Hydrogels: Learn About Water Crystals In Potting Soil

If you’re a home gardener who spends any time browsing in garden centers or on the Internet, you’ve probably seen products that contain water retention crystals, soil moisture crystals or moisture beads for soil, which are all just different terms for hydrogels. Questions that may come to mind are, “What are hydrogels?” and “Do water crystals in potting soil really work?” Read on to find out more.

What are Hydrogels?

Hydrogels are small chunks (or crystals) of man-made, water-absorbing polymers. The chunks are like sponges – they hold a tremendous amount of water in comparison to their size. The liquid is then released gradually into the soil. Various types of hydrogels are also used in a number of products, including bandages and wound dressings for burns. They are also what makes disposable baby diapers so absorbent.

Do Water Crystals in Potting Soil Work?

Do water retention crystals actually help keep soil moist for longer periods? The answer is maybe – or maybe not, depending who you ask. Manufacturers claim the crystals hold 300 to 400 times their weight in liquid, that they conserve water by releasing moisture slowly to plant roots, and that they hold up for about three years.

On the other hand, horticultural experts at University of Arizona report that the crystals aren’t always effective and may actually interfere with the water-holding capability of the soil. The reality is probably somewhere in the middle.

You may find the crystals convenient for keeping potting soil moist while you’re away for a couple of days, and they may extend watering a day or two during hot, dry weather. Don’t expect hydrogels to serve as miracle solutions for extended periods of time, however.

Are Moisture Beads for Soil Safe?

Again, the answer is a resounding maybe, or maybe not. Some experts say that polymers are neurotoxins and they may be carcinogenic. It’s also a common belief that water crystals aren’t environmentally safe because the chemicals are leached into the soil.

When it comes to water retention crystals, they are probably convenient, effective, and relatively safe for short periods, but you may choose not to use them on a long-term basis. Only you can decide if you want to use soil moisture crystals in your potting soil.

Water retention crystals, soil moisture crystals or moisture beads for soil are all just different terms for hydrogels. Questions that may come to mind are, ?What are hydrogels?? and ?Do water crystals in potting soil really work?? Click here to learn more.