Ever wonder why some plants survive and even thrive with little water, high heat, and intense sun, while others struggle and die? The answer lies in their anatomical characteristics.
Plants dubbed ‘’drought-tolerant,’ or what Sunset Western Gardening Book terms ‘water-wise,’ need little supplemental watering. Broadly speaking, these troopers have adapted their biology to:
- store water or trap moisture in leaves, stems, or flowers
- limit water loss through evaporation or transpiration
- keep the plant cooler by reflecting sunlight or providing some shade
- seek water from Mother Nature
As Matthew J. Diserio of Water Asset Management expressed in Investors are Mining for Water, the Next Hot Commodity, “Water is the scarce resource that will define the 21st century, much like plentiful oil defined the last century.” Homeowners are mining for water too, as shortages force them to convert water-intensive lawns and plantings to water-wise alternatives.
The trick is to choose plants endowed with low consumption/square foot and hot, dry adaptive traits. Consumption/square foot can be calculated from water use and mature sizes noted on nursery tags and countless online lists. A handful of traits can be found in references such as Purdue University’s Plant Diagnostic Laboratory and Green Garden Group’s The Drought Tolerant Garden.
The comprehensive set of 15 traits below, each with representative plants, is derived from systematic analysis of available resources. An X in a column indicates that trait has that anatomical adaption. The more X’s a plant has, the more it tends to tolerate the stress of little water.
|Water-wise Plant Traits
||1. Store or trap moisture
||2. Limit water loss
||3. Keep plant cool
||4. Seek water
|1. Spongy leaves and stems that suck up water, e.g. Aloe, agave||X||X|
|2. Hairs that reflect light, grab water, slow airflow, e.g. Lamb’s ear, lavender||X||X||X||X|
|3. Small leaves or needles with less surface area, e.g. Rosemary||X||X|
|4. Lacy foliage with deep indentations, e.g. Russian sage, yarrow||X||X|
|5. Waxy coatings that reflect light, hold moisture, e.g. Pittosporum, sedum, aloe
|6. Stiff, leathery leaves that hold onto water, e.g. Madrone, oleander||X||X|
|7. Summer-dormant plants that drop leaves, e.g California buckeye. black sage||X|
|8. Gray, silver, or white foliage that reflects light, e.g. White sage, variegated
|9. Vertical leaves that avoid midday sun, e.g. Manzanita, prickly pear||X||X|
|10. Restricted growth of leaves and stems, e.g. Cacti||X|
|11. Long, narrow leaves or needles that shed heat, e.g. Native grass||X|
|12. Spines that provide some shade, e.g. Barrel cactus||X|
|13. Aromatic oils that cool plant or lessen loss, e.g. Chaparral, sage, thyme, rosemary
|14. Long roots to tap deep groundwater, e.g. California oak, olive
|15. Lateral root network to soak up rain and fog, e.g. Native ceanothus, California oak