Water when?

The rule of thumb is ‘Water during growing season.’ Plants grow in spring and summer as temperatures heat up, and any supplemental water occurs then, right? It is not that simple for dry-climate plants.

Some are warm-season growers that push out new growth in spring through fall and go dormant in winter. Others are cool-season growers that add mass in fall through spring and go dormant in summer to protect themselves from heat. All need water once or twice weekly to once monthly while growing, and little to none while dormant. Gardening practices attuned to plants’ innate seasonality improve health and conservation.

Yet which are warm and which are cool is not immediately obvious. Discrete genus reports such as Geoff Stein’s “Introduction to Aeoniums” and brief remarks in Robin Stockwell’s Succulents identify some. James Feucht, PhD, 2005 Colorado State University Cooperative Extension, groups dormancy of many succulents below, with a caveat of anomalies for a few species:

Plant descriptions may someday specify growth season alongside height/width, exposure, and water use. Until then, discover a plant’s cycle and irrigation need with these 4 techniques:

  1. Ask experts at horticultural organizations, nurseries, or online resources.
  2. Find clues in a species’ origin. Natives or Mediterranean-climate origins tend to grow when warm, whereas those from tropical or subtropical regions of Africa and the Americas tend to grow when cool.
  3. Observe species’ growth and dormancy in your own or others’ gardens over the course of a year or two.
  4. Survey source materials for indicators. ‘Summer dry’ notations at San Marcos Growers or ‘Hot and dry’ sorts at Annie’s Annuals, for instance, hint cool-season grower.