A helpful tool in keeping potted plants properly hydrated is water absorbing pellets that soak up water and swell, releasing it slowly over time back into the surrounding soil at the plant roots. These hydrogels, according to Texas A&M University, are starch-based and can absorb more than 100 times their weight in water. The pellets are mixed throughout the potting soil at planting time and will refill with moisture each time the pot is watered thoroughly. They are safe to use in edible as well as ornamental potted plantings.
Determine the amount of hydrogel pellet material to use by consulting the directions label on your container or bag. There will be a recommended amount to include based on the volume of soil your pot can hold, less the size of the rootball. Adhering to the label recommendation, at least roughly, will prevent spillage of the soil and plant over the top of the pot once the polymers have absorbed water and swelled. More isn't better and too much can lead to a mess the first few times you water.
Mix the recommended amount of pellets into your potting soil evenly and fill the pot with the mix so that the pellets are well distributed throughout the pot from top to bottom. Place your plant in the potting mix and firm the soil gently around the roots. Leave a watering gap of at least an inch or two between the lip of the pot and soil surface to allow for pellet expansion.
Water gently and slowly with tepid to cool water to completely saturate the potting soil, until water streams out of the drainage holes at the bottom of the pot. The pellets will swell as they absorb water and if you have used too much of the material the excess may swell above the edge of the pot and can be removed. Drench the soil each time you water to rehydrate the pellets.