Many Pacific Northwest (PNW) native plants have a natural tolerance for summer dry periods common in the near- Mediterranean climate found west of the Cascade Mountains in Oregon and Washington. These plants include species growing in woodlands, savannahs, meadows and vernal pools (seasonally wet meadows that dry out in the summer months).
Your drought tolerant plants will perform best and require less care if you group them together; a concept called “zoning”. Pay attention to the sun/shade and drainage requirements.
During establishment, provide enough water to encourage development of a healthy root system. This can take 2-3 years. Reduce the amount of extra irrigation gradually and watch carefully for signs of water stress, such as wilting or curling leaves, or a “dull” appearance of the leaves, during these years.
Some PNW natives, the wild bleeding heart (Dicentra formosa) and lady fern (Athyrium filix-femina) for example, die back naturally during the dry summer months.
Many PNW native plants do better in landscapes that receive only minimal irrigation in summer months. One example is the Oregon white oak, Quercus garryana, which is subject to root rot if irrigated. Another is the seasonal wetland bulb Camas, Camassia species, which requires summer dry periods to prevent rotting of the bulb. Some spreading species, pearly everlasting (Anaphalis margaritacea), for example, will spread rapidly in wet conditions, becoming a garden pest.
Look to neighboring ecosystems for other drought tolerant plants. Examples of plants that do well in western Oregon are the golden currant (Ribes aureum), native east of the Cascade Mountains, and California fuchsia (Epilobium canum), native to California.
Plants that are not drought tolerant include those found in year-round wet ecosystems, some riparian (stream and riverbank) areas, and mountain foothills in moist woodlands or meadows.
The following list of plants are recommended for Water-Wise gardens:
- Western red cedar (Thuja plicata)
- bitter cherry (Prunus emarginata)
- Pacific madrone (Arbutus menziesii)
- Oregon white oak (Quercus garryana)
- Ponderosa pine, Willamette Valley form (Pinus ponderosa)
- Blueblossom (Ceanothus thyrsiflorus)
- red flowering currant (Ribes sanguineum)
- red osier dogwood (Cornus sericea)
- blue elderberry (Sambucus mexicana)
- red elderberry (Sambucus racemosa)
- evergreen huckleberry (Vaccinium ovatum)
- hairy manzanita (Arctostaphylos columbiana)
- mock orange (Philadelphus lewisii)
- oceanspray (Holodiscus discolor)
- Oregon grape (Berberis nervosa)
- tall Oregon grape (Berberis aquifolium)
- Nootka rose (Rosa nutkana)
- western serviceberry (Amelanchier alnifolia)
- wavy-leaved silk-tassel (Garrya elliptica)
- Kinnikinnick (Arctostaphylos uva-ursi)
- coastal strawberry (Fragaria chiloensis)
- wild strawberry (Fragaria virginiana)
- woods strawberry (Fragaria vesca)
Herbs and Ferns:
- Douglas aster (Aster subspicatus)
- blue-eyed grass (Sisyrinchium bellum)
- camas (Camassia sp.)
- western red columbine (Aquilegia formosa)
- goldenrod (Solidago sp.)
- Douglas iris (Iris douglasiana)
- Oregon iris (Iris tenax)
- Oregon sunshine (Eriophyllum lanatum)
- pearly everlasting (Anaphalis margaritacea)
- Cascade penstemon (Penstemon serrulatus)
- broadleaf stonecrop (Sedum spathulifolium)
- sword fern (Polystichum munitum)
- yarrow (Achillea millefolium)
- California poppy (Eschscholzia californica)
- farewell-to-spring (Clarkia amoena)
- globe gilia (Gilia capitata)