Advice

RHS Help & Advice

Water-retaining granules

The most successful water-storing gels or granules are based on the synthetic polymer polyacrylamide, which can absorb and release moisture over an extended period.

They are intended for incorporating into growing media and soils to increase water-holding capacity. Manufacturers claim that an increase in soil water-holding capacity of 300 - 800 percent is possible in some soils. Gels are also able to absorb nutrients supplied in soluble plant foods and reduce leaching of these in poor soils.

Usage

Gels should be of most benefit where evaporation from soil is high, soil moisture-holding capacity is low, plants are growing rapidly and frequent attention to watering is needed. Their use could be advantageous as compost additives for hanging baskets that dry out rapidly, plant containers positioned on a sunny, hot patio, or where roots are badly damaged when re-siting well-established shrubs.

Benefit to plants

While the main physical attributes of water-storing gels is acknowledged, their impact on plant growth is less conclusive, some reports showing increased growth levels, others not. Variables of soil texture, climate, and moisture requirements of different species make evaluation difficult.

Further information

RHS guidelines on the use of water in the garden - water-wise gardening.

RHS Practical Guide - Drought Resistant Gardening is a handy pocket-sized reference book with tips on gardening with a limited amount of water and the best plants for your situation.