All plants need water. It fuels foliage development, blossom production and fruit growth. Without water, plants wilt, shrivel and die, and constantly drought-stressed plants are more prone to disease. Though watering needs vary by plant, various general watering principles and strategies can ensure proper hydration for your garden while conserving water for your utility bill.
Every type of plant has different watering needs. For example, tomatoes need upwards of 32 ounces of water a day while herbs such as basil need less. A general guideline, according to Washington State University, is to moisten the entire root zone of the plant--the area in which the plant extends its roots--and wait to water until the soil has dried.
Sandy soils dry out rapidly due to their porous nature. Gardeners should pay careful attention to ensure that plants growing in such soil aren't showing signs of drought stress (e.g. wilting or yellowing of the foliage). Clay soils drain very slowly and are more prone to being overwatered, which can lead to plants being drowned or rotting.
The optimum time to water plants is in the early morning, according to the University of Illinois. This provides the hydration that plants need to handle the drying effects of the sun and afternoon heat. Moisture applied in the morning also has time to evaporate off of the plant surfaces, minimizing the chances of common fungal diseases like verticillium wilt. If you water in the evening, moisture sits on the plants all night, and encourages fungi.
All plants benefit from mulch. Not only does mulch conserve water by helping to ward against evaporation, but mulch also blocks out weed invasions that might compete with the plants for soil moisture. A layer of mulch that measures 3 to 4 inches deep is usually sufficient, according to the University of Arizona. Mulching materials include shredded grass clippings, wood chips and weed-free straw.
Unless a plant has specific watering needs, most plants benefit from deep watering sessions that reach the depth of the plant's root network rather than shallow watering. The latter encourages the roots to stick close to the soil surface, making the plant more susceptible to drought. Most annuals, lawns and vegetable plants should be watered so the soil is moist to a depth of 12 inches; 24 inches for shrubs; and 3 feet for trees, according to the University of Arizona.