People outside of the Pacific Northwest may think it rains here year-round, but last year’s extreme drought was a good reminder of how dry the air and soil can get when it is not raining. The majority of moisture we get each year falls between October and April. Last year Seattle set a new record for the hottest and driest period from May through July. This weather was tough for people and plants alike. Still, even when we are not in a drought, it can be challenging to keep lush foliage and flowers thriving through the summer without spending all of one’s time watering to keep plants alive—only to watch them drown in the winter.
Adaptable Native Plants
Hot, dry summers may be short, but they are the norm for our Maritime climate. Many native plants have adapted to this cycle of cool and wet winters, and hot and dry summers. Once established, a landscape filled with Northwest native plants can be fairly easy to maintain since many of these plants will not require watering in the summer once they are established — unless under extreme drought conditions.
The real challenge comes when soil does not drain well. If the garden is in a low spot (i.e. at the base of a hill) or if the soil contains a lot of clay, many plants that are more drought-resistant may die during periods of heavy, prolonged rainfall. Poor drainage can cause the roots to rot and be more susceptible to disease. Drought-tolerant shrubs such as rosemary and thyme may not make it through winter despite temperatures that stay above freezing if they are planted in soil that does not drain well.
Vine maple, red osier dogwood, salal, Douglas’s spirea, snowberry, deer fern and western sword fern are all native to our region and will tolerate soggy, as well as bone dry, soils once they are established. However, many of these plants may not do as well in full sun. Salal can grow in both full sun as well as full shade, but deer fern prefers only shade. Find lists of native plants for a variety of conditions (i.e., sun or shade, moisture preference, habitat and more) at King County’s Native Plant Guide: https://green2.kingcounty.gov/gonative. Washington Native Plant Society is another excellent resource: www.wnps.org.
Rain Garden Plants for Tough Spots
Rain gardens are made up of different zones with varying amounts of wetness and dryness depending on the season. Native plants are often included in rain garden planting plans because of their ability to grow in these varying conditions. Zone 1 is the wettest part of a rain garden because it is the lowest. It is located in the center. Zone 1 plants must be able to survive having their roots submerged in water during heavy rain events but also tolerate very little water during summer dry spells. Slough sedge (Carex obnupta) and Dagger-leaf rush (Juncus ensifolius) are able to survive in these conditions. .Zone 2 is the middle area located along the side slopes. It helps stabilize the slopes. Zone 2 plants also need to tolerate intermittent standing water. Dwarf red-twig dogwood (Cornus sericea) and boxwood honeysuckle (Lonicera pileata) will do well in sunny as well as shady rain gardens. Zone 3 encompasses the top perimeter and adjacent area. These plants can take drier soil. Drought tolerant sword fern (Polystichum munitum) and evergreen huckleberry (Vaccinium ovatum) are good choices if the area is shady; yarrow (Achillea) and coastal strawberry (Fragaria chiloensis) are both natives that will thrive in a dry sunny spot.
Edible Plants
There are a few shrubs that bear edible fruit and are fairly tolerant of both wet and dry soils. They may not do well in bog-like conditions like a rain garden’s Zone 1 during a winter storm, but will can tolerate more saturated winter soils as well as dry summer soils. Aronia or chokeberry shrubs produce red, black and purple sour berries that can be eaten raw or made into juice, jam, wine, tea and more. Black chokeberry (A. melanocarpa) has a high concentration of polyphenols and anthocyanins in particular.
Darwin’s barberry (Berberis darwinii) produces pretty orange flowers in early spring that are followed by blue berries loved by birds. The berries are often overlooked by people but the seedy fruits can be eaten raw or cooked. Black elderberry (Sambucus nigra) is considered a valuable medicinal herb with edible flowers and fruits. Take care with this plant; leafs, stems and branches are poisonous and berries should be cooked or properly processed before eating.
Daylilies are perennials that can grow just about anywhere, provided they get some sun. They come in a range of colors and some cultivars such as ‘Stella de Oro’ will keep blooming throughout the season as long as you keep them deadheaded. The tubers, early spring shoots, flower buds and flowers are all edible. The buds are said to make great pickles too!
Many more trees, shrubs, perennials, ferns and grasses will do just fine in soils that are wet in winter and dry in summer. Our summers are short enough as it is; why spend all your time and money watering when you could be smelling the flowers instead?
For more information on plant selection for all garden situations, visit the Garden Hotline online at www.gardenhotline.org or call us at 206-633-0224. You can also find us on Facebook, Twitter, Pinterest and YouTube.