Plant Water Needs

We recommend that you familiarize yourself with how much water your plants need. Plants in this program are categorized into one of three irrigation categories depending on the optimum amount of water needed for good health. These are: very low, low, and medium. If you have already selected plants from the Garden Gallery, Garden Tours, and/or Plants sections of the website and you printed a hyrdozone report, the plants you selected will already be separated into their water need categories.

To determine the water need category of an existing plant go to the Home and click Plants. Then look up plants by common or botanical name. While this website has an extensive plant list, it is not a complete list. Consult the Internet, library, plant societies or clubs, and local nurseries for information on plants that are not included.

The following are rules of thumb when watering. Ultimately, however, a visual assessment of the health and vigor of your plants is your best guide.

  • "Very Low" plants can survive with 3 to 6 deep soakings during a dry summer.

Romneya coulteri - Matilija Poppy (aka Fried Egg Plant) Once established, does not need extra watering.
Very low water requirement plant
  • Many annuals, as well as fruits and vegetables, require the soil to be kept moist throughout the growing season if they are to bloom well, or produce a good crop.

  • Water young plants often; they have small root systems and tend to dry out quickly. Older plants have established root systems with plenty of root hairs (the organs that collect the most water for the plant); they do not need as much water as younger plants.

  • Under hot, dry, and/or windy conditions, plants use water rapidly. Young or shallow-rooted plants may need extra water, as they cannot absorb enough water to keep foliage from wilting.

  • Water plants at night between 2:00 a.m. and sunrise. Watering in midday when the weather is hot, dry, or windy can waste water due to excessive evaporation. Watering late in the day will keep the soil surface wet all night increasing the chances of soil-borne fungi damaging garden plants.

Knowing how much water different plants may need becomes crucial during hot summer months. Here are a few general rules:

  • High water-use plants, such as turf, will need watering 3 to 4 time per week. Turf is shallow rooted, and fast growing, requiring frequent irrigation.

  • An 800-square-foot lawn uses 2,000 to 4,000 gallons of water per month depending on the turf/grass type and climate.

Shallow roots of turf grass.
Turf with shallow roots
  • Moderate water-use plants (everyday ornamentals) need watering 2 times per week.

  • Low water-use plants need only 1 watering day per week.

  • Very low water-use plants will need no more than 1 watering day every other week.

For more tips on watering schedules, go to the Watering Guide found on the Home.