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Home > Resources> Garden Solutions > Irrigation Practices


Irrigation Practices

We list a suggested irrigation regime for each plant we grow. These regimes range from the driest growing plants we grow at "No Irrigation Required" to our most moisture loving classification of "Aquatic Plant". Please note that irrigation requirements of a plant, both the frequency and duration of the irrigation, will vary widely depending on climatic and soil conditions. Our observations and suggestions are made at our site on the eastern end of the Goleta Valley in Santa Barbara, California where the climate is typically mild and the soil a well drained loam. Water requirements will likely be greater in hotter inland valleys and gardens to the south of Santa Barbara and may be less in cooler coastal northern California gardens. The age of the plant is also a major factor - newly installed landscapes of even the most drought resistant plants may require frequent irrigation while established plantings will likely not. All of these factors must be taken into consideration. There is absolutely no way for us to recommend how much water a plant will need in different situations and, for this reason, our recommendations are given in a range of what we think would be typical for the plants we list. There is no substitute for knowing your own climate and how your soil retains moisture. We recommend that all gardeners use a soil probe or similar device to get a profile of soil moisture at the surface and deeper near the plant roots. Irrigation contractors and university researchers use soil probes to determine soil-moisture level by inserting the soil probe into the ground, pulling it out and then feeling and seeing the soil in it. This simple test can answer a lot of questions.

The irrigations classifications used on our website are described below.

No Irrigation Required
Plants that have this irrigation recommendation are the most drought resistant plants that we grow. We feel that once established in the landscape, these plants can survive, given normal rainfall, in gardens in our coastal climate. These plants likely would respond favorably to some supplemental irrigation but this should not be required for the survival of the plant. These plants may require irrigation in hotter inland or locations further to the south of Santa Barbara.

Low Water Needs
These plants might survive on normal rainfall in our coastal climate but definitely respond to occasional but infrequent irrigation. In our own test gardens plants in this category, once established in the landscape, would be given a deep irrigation every 4 to 6 weeks.

Medium Water Needs
These plants require a regular irrigation regime to persist and be presentable in the garden. These plants are not necessarily considered "thirsty" and include most of the plants in the typical urban landscape. In our cool coastal climate these plants, once established in the landscape, would require irrigation once a week to once every other week. In hotter and drier times of the year, some of these plants may require more frequent irrigation and may also not require any supplemental irrigation during winter or when spring rains are abundant.

High Water Needs
These plants are water lovers and require weekly irrigation or more. In hot dry conditions during summer months these plants may require irrigation every few days. Many of these plants are native to bog or riparian conditions or have extremely shallow roots. While we try not to grow many plants with these requirements, some of these plants are just too attractive so we need to put up with their special needs. Often these plants do well in containers where their watering requirements are not so different from plants that would require less irrigation if planted in the ground. Sometimes these conditions can be met by growing these plants on the edge or in elevated pots within a water feature.

Aquatic
These plants are best grown in water or in soil that is kept evenly moist.

Other Resources
Our nursery was involved in a statewide project organized by the University of California Cooperative Extension and the California Department of Water Resources. This project sought to determine the irrigation needs of ornamental plants and make recomendations for irrigation practices for many areas of our state. This project, called Water Use Classification of Landscape Species (WUCOLS,) categorizes the most commonly used ornamental plants, assigning a relative value to the irrigation required for each plant. In late 2014, 22 years after the first WUCOLS study, WUCOLS I was published and 15 years after the last edition, WUCOLS STUDY III, the new online version WUCOLS IV is now available on the University of California Division of Agriculture and Natural Resources Website.

Another valuable resource, espceially for turf irrigation is the California Irrigation Management Information System (CIMIS). This is a program in the Office of Water Use Efficiency (OWUE), California Department of Water Resources (DWR) that manages a network of over 120 automated weather stations in the state of California. The CIMIS system was developed in 1982 by the California Department of Water Resource and the University of California at Davis to assist California’s irrigators manage their water resources efficiently. More information on this can be found on the CIMIS website.