Terra-Sorb

If you'd like to reduce your frequency of watering and risk of drought damage, consider adding Horticultural Grade Terra-Sorb (AKA Super-sorb) or any generic water absorbing crystals to your soil. It absorbs 300 to 400 times its weight in water and slowly releases it. It's non-toxic, non-hazardous to the environment, and compatible with fertilizer. Apply at a rate of 1 pound per 100 square feet for each 2 inches of depth by raking or tilling into the ground 2-4 inches (or mix 1/2 teaspoon into the soil under/around each individual plant).

Terra-Sorb (or generic water absorbing crystals) is available at many garden supply stores and online in quantities ranging from 3 ounces to 40 pounds See Terra-sorb's Product Directions and Material Safety Data Sheet

Note: people have a tendency to use too much, sometimes to the point where the expansion is so great that the plants pop out of the ground! The simplest way to avoid this is to put some of the crystals in a bucket, add water, wait 10 minutes so they expand, and then add them to the soil. This way they can only expand back to their current size and the plants will stay put. Do not worry about adding too much water, you can scoop them up like chunks of jello off the bottom.