Water Absorbing Polymers In Containers

Growing plants in containers is fun and very satisfying. However, one of the drawbacks of a container garden is that it needs watering more often than does the soil in garden beds. In fact, a container planting can dry out very quickly causing great stress on the plants.

While it is optional, we advise yardeners to include a water absorbing polymer gel with the potting mix when setting up a container garden. These magical crystals will cut your watering needs by one third to one half. You can buy soilless mix with these polymer crystals already included, or you can introduce the polymers yourself as you prepare to plant your container. For details on how these water absorbing polymers work go to Understanding Polymers.

Important Note – Water absorbing polymers are not appropriate in self-watering containers.

Polymer Gels can be mixed with the soil mix in either dry or wet (hydrated) form. Although the crystals become somewhat gooey and gloppy when hydrated, it is much easier for beginners to container gardening to determine the proper proportions of gel to soil when they are in this state. To hydrate the crystals, start off with a teaspoonful in a cup of water (or a tablespoon in a pint). Let it sit for an hour or two, then observe how much of your particular brand of crystal it takes to fill the container with fully hydrated, jelly-like material. It takes anywhere from 30 minutes to several hours for the material to absorb all the water it can hold. Now you are ready to mix the gel with soil.

A mixture of about 1 part hydrated gel to about 8 parts soil mix is appropriate for most container applications that will not be in direct sun. For a container located outside in direct sun where drying out is a constant risk, the 6 to 1 ratio is best. Polymers are one of those products, like fertilizer, where “just a little more won’t hurt” is a bad idea. Exceeding the recommended amounts may result in your plants being pushed right out of the soil as the overabundance of gel crystals absorb water and swell.

While you can add dry Polymer Gel to plants already established in pots (there are products for just that purpose), the material will be more effective if you take the trouble to transplant an established plant into a pot with the soil and gel thoroughly mixed.

How Much to Water With Polymers In Your Container
Added to a soil mixture as dry crystals, Polymer Gels take a week or two to become fully activated in terms of being able to absorb and release water easily. During this time it is important to water, if there is no rain, so that the crystals can become hydrated. Plant roots also need time to grow into contact with the gel crystals so they can extract the available water. During this period, water as you have in the past as if there are no crystals in the mix. If you hydrated your polymer crystals before mixing them with your soil mix you can cut back on watering within a week. .

After a couple of weeks or so the gels should be activated. It may still be difficult to determine whether it is okay to reduce the frequency of watering, because the surface soil may be dry to the touch even though the gel crystals deep within still contain plenty of water. Unfortunately, water meters sold for houseplants do not work with soil that contains Polymer Gels.

A good guideline is to water Polymer Gel treated soil about one third to one half as often as you watered the untreated soil. For example, if you previously watered your container twice a week, water it now once a week. In the beginning you may err on the side of watering a bit too much. If the soil mix drains well, as it should, the plants will suffer no ill effects. If the soil drains well, it is virtually impossible to over water a plant sitting in a soil with Polymer Gels in it. At the same time, the dry crystals will not recharge and absorb water if water is not readily available. Outdoors a steady rain of more than 1 inch will do the job nicely.

For information about buying Water Absorbing Polymers click here to go to the Yardener’s Tool Shed.

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