Water Use Classification of Landscape Species (WUCOLS)

WUCOLS Update: August 2022

We are pleased to announce that the WUCOLS update process has now been completed!  Funding for these upgrades was provided by the California Department of Water Resources.  Here are some highlights of the changes to the WUCOLS database:

  • New search page design
  • Improved search process that is faster and updates any search parameter changes instantaneously
  • Interactive Google map to find city of interest
  • Interactive map feature to find city of interest
  • Hi-resolution photos and cultural information for approximately 1,200 low- and very low-water use taxa.  Hi-resolution photos are downloadable for your use.
  • Interactive database allowing for the creation of your “Favorite” plant list and ability to download, export and save to Excel
  • Create WUCOLS information (bench) cards of your “Favorite” plants downloadable in two size formats
  • QR codes can be generated and printed for your “favorite” plants 

Please let us know your opinion about the recent changes to the WUCOLS database in this Feedback Survey.  For any database technical issues, please contact Dave Fujino (dwfujino@ucdavis.edu).

Water conservation is an essential consideration in the design and management of California landscapes. Effective strategies that increase water use efficiency must be identified and implemented. One key strategy when landscaping is to group plants with similar water requirements.  By supplying only the amount of water needed to maintain landscape health and appearance, unnecessary applications that exceed plant needs can be avoided. Doing so, however, requires some knowledge of plant water needs.  The WUCOLS searchable database allows you to create your “favorite” plant list by water needs (very low, low, moderate and high) for your climatic region.

WUCOLS IV provides evaluations of the irrigation water needs for over 3,500 taxa (taxonomic plant groups) used in California landscapes. It is based on the observations and extensive field experience of thirty-six landscape horticulturists (see the section "Regional Committees") and provides guidance in the selection and care of landscape plants relative to their water needs.

Home Page Photo
WUCOLS IV provides an assessment of irrigation water needs for over 3,500 taxa. Photo by Ellen Zagory.

Current Update: The 4th Edition (2014)

The 4th edition (Costello, L.R. and K.S. Jones. 2014. WUCOLS IV: Water Use Classification of Landscape Species. California Center for Urban Horticulture, University of California, Davis.  http://ucanr.edu/sites/WUCOLS/) represents a substantial expansion in the number of plant evaluations. Over 1,500 entries have been added to the 3rd edition list, for a total of 3,546 entries. Essentially, the great majority of taxa available from wholesale nurseries in California are included.

Unlike the 3rd edition, the 4th edition includes evaluations of many cultivars and hybrids. For a number of species (e.g., Ceanothus spp.), water needs of cultivars were thought to be sufficiently different than water needs of the species and were evaluated separately. In addition, a number of cultivars do not have a specific epithet, such as Erysimum ‘Bowles Mauve’, and the species from which it is selected is not obvious. Hence, only the cultivar could be listed.

In addition, a number of species evaluations made in previous editions were revisited by the regional committees. If the committees believed that the evaluation of plant water needs should be changed (raised or lowered), it was changed. In some cases, a “?” was replaced by VL, L, M, or H (see the section “Categories of Water Needs”). As a result, users should be aware that species assignments from WUCOLS I, II, or III may not be the same as those found in WUCOLS IV.



If you are using the WUCOLS list for the first time, it is essential that you read the User Manual. The manual contains very important information regarding the evaluation process, categories of water needs, plant types, and climatic regions. It is necessary to know this information to use WUCOLS evaluations and the plant search tool appropriately. To access the User Manual, click on the tab and view specific topics.