How to use irrigation Schedule 4 for moderate water use plants


Water is essential to the growth and health of our landscape plants. Over 97% of water used by plants is needed to cool their leaves and stems; the remaining water is needed for growth of roots, stems and leaves. In nature, this water comes from rainfall; in gardens we commonly provide supplemental water with our irrigation systems.

Supplemental water needs variables

The amount of supplemental water we apply can vary throughout the year and is mostly influenced by the types of plants, seasonal climate, microclimates, soil types.

Our garden plants come in many different sizes and shapes. Plants that have the most leaves often need the most water for cooling. This means our trees often need more water than smaller shrubs and ground covers. Succulents and cacti have an advantage by storing water in their stems for use when conditions are dry. Many California native and Mediterranean plants have adapted to summer conditions with leathery leaves, and also by becoming inactive when soil conditions are dry.
Due to the many types of plants we can grow in our gardens, we recommend selecting and combining plants with similar water needs together and applying appropriate amounts of water to each group. This technique leads to different garden moisture zones, or hydrozones, that can be watered on separate irrigation valves.

Seasonal water use

As might be expected, we apply the most water to our gardens from April through October after winter rains are finished and when the days are longest and temperatures highest. We also provide more water to plants growing in sunny areas and when they are flowering. Less supplemental water is needed in the winter months when temperatures are cooler, days are shorter and when we have seasonal rains.

Irrigation Schedule 4
moderate water use plants

Irrigation Schedule 4 has been developed for Moderate Water Use Plants that grow best without experiencing moisture stress throughout the year. The Irrigation Schedule and Graph shown below, has been designed to provide you with the baseline amount and frequency of supplemental irrigation water for each month for these plants. From April through October, we need to apply from 2 to 4 inches of water per month to sustain good plant health and plant character. As can be seen, this schedule requires you to adjust your irrigation schedule to offset the hottest months of summer for these plants. In contrast, when winter rains do not average 3 inches per month, we need to apply winter irrigation to make up the deficit.

An Irrigation Schedule and Graph has been prepared for four different groups of plants depending upon their supplemental water needs. Supplemental water is organized on a monthly basis as well as volume and number of irrigation applications. The objective is to water deeply and infrequently. Again, we want to add moisture to the top 12-15 inches of soil where possible and to encourage deep root depth within our plants. In practical terms, we try to provide at least 1 inch of water each time we irrigate, and we will water one, two, three or four times a month depending upon the water needs of our particular plants.

Each baseline schedule and graph is a recommended starting point for your garden water needs. However, it is always necessary to study your garden conditions and adjust this schedule to fit the seasonal and microclimate variations, including heat waves, droughts, and winter rains (that can provide all the winter moisture needed so your irrigation system can be shut off). This requires you to be vigilant and make garden observations and adjustments to this baseline schedule for it to work best for you.

Scroll horizontally to see the full table

  Jan* Feb* Mar* Apr May Jun Jul Aug Sep Oct Nov* Dec*
Runs per Month 0x to 3x 0x to 3x 0x to 3x 2x to 3x 2x to 3x 3x to 4x 3x to 4x 3x to 4x 2x to 3x 2x to 3x 0x to 3x 0x to 3x
Inches per Run 1" 1" 1" 1" 1" 1" 1" 1" 1" 1" 1" 1"
Inches per Month 0" to 3" 0" to 3" 0" to 3" 2" to 3" 2" to 3" 3" to 4" 3" to 4" 3" to 4" 2" to 3" 2" to 3" 0" to 3" 0" to 3"
  • Range of supplemental summer water: 17"-24"
  • Range of supplemental winter water: 0"-15"
  Jan* Feb* Mar* Apr May Jun Jul Aug Sep Oct Nov* Dec*

Look at Irrigation Schedule 4 above. For plants assigned to Irrigation Schedule 4 we have provided you with a chart that shows how many times to water each month (Runs per Month) and how much water to apply during each application (Inches per Run), and the total amount of monthly supplemental water (Inches per Month) needed to sustain these plants.

As you can see, water needs for plants assigned to Irrigation Schedule 4 need 2 to 4 inches of supplemental water from April through October. More water is needed during the hottest summer months and for plants growing in hotter and sunnier garden locations. Winter irrigation is needed only when winter rains are less than 3 inches per month from November through March. The chart also indicates to apply 1 inch of water during each irrigation cycle.

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