Get Growing: Growing drought-tolerant plants in the Pacific Northwest

As climate change ramps up the heat with each summer, many people see the term “drought-tolerant” as a shining beacon of hope on a plant tag, promising to free their backs and their water bills from hours spent watering parched flowers and shrubs.

Imagine a bed that takes care of itself — offering carefree color, shrugging off weeks of drought, saving water while delighting pollinators (why not plant some nourishment for the bees while you’re at it).

That would be wonderful, but, of course, there’s more to it than just switching out your roses for succulents and grasses and calling it xeriscaping.

I’ve been experimenting with plants' drought-tolerance levels parking strips because my hose barely reaches them. The other name for parking strips is “hell strips,” and ours are well named.

Not even counting the toxic fertilization by dog visitors (including our own, when I’m not looking), the soil is typically compacted, and the south-facing heat radiating from the 360-degree concrete cooks the bed like an oven — in fact, if we roofed part of it, we could probably make pizza.

Some plants are “rescued” from the compost pile at the nursery to find a hardscrabble life here. If I could ask them, they might opt for the compost pile instead.

Before I began amending the soil, my shovel would clang on contact. Slowly, lasagne-style, I’ve been adding layers of organic material like arborist wood chips, straw and coffee grounds to compost down and help dissolve that hardpan. So plants have 3 to 4 inches of pillow top before they get a rude awakening. It’s also only 3 feet wide, so it’s piled high in the middle, and water runs off quickly.

While I’m usually pretty good matching plants to sites, the “What was I thinking?” award goes to the time I tried a Haruko Nishiki willow here. Willows like moisture so much, their roots tunnel miles to get it, and within two weeks the poor thing turned into brown tissue paper. Luckily, I noticed in time to transplant it, and now it rules over a partially shaded bed at 7 feet tall.

Some of the star survivors who stick around with little encouragement from me or the hose are:

Agastache Blue Boa; Rose Flower Carpet Amber; Echinacea Sombrero Something (lost tag syndrome: It’s an orange-red in the Sombrero series); a dark-leafed ajuga; all the Euphorbias; a weeping Deodar cedar (Cedrus deodara); Heuchera Lime Marmalade; Stachys lantana (lambs ears); Darwin tulips and spring-blooming bulbs; Helichrysum italicum (a.k.a. curry plant, sold as an annual for its silver foliage); Blue Oat grass; and self-seeding annuals calendula and nigella are staking out multiple colonies.

What most of these have in common is they prefer to be warm and dry. They make it through the wet winter because the soil drains so well and the concrete keeps it warm.

The rose is the big surprise win, since most rose hybrids demand an entourage to feed, spray and prune them. This “ground-cover” style rose, actually about 3 feet tall and wide, has thicker, glossier foliage, which is more disease and drought-resistant, and thrives with a little deadheading. It could thrive more with more fertilizer.

The weirdest flop? Trailing succulents and creeping thymes cannot get a foothold here. I think user error was the culprit; they are so tiny, they need more consistent water to establish. It’s worth repeating (to myself, apparently) that all plants need supplemental water getting established for up to two years in our dry spring and summers.

Having tried multiple sunny locations in the yard to grow Agastache, I finally found success in the parking strip. Planted last year, Blue Boa has been a knockout all spring and summer, for me and the bees, who use it like a lunch buffet. As with the echinacea, I’ll leave all the Agastache’s old stems up through the winter to help insulate the plant from the wet and cool temperatures. This is my rule with anything marginally hardy or like their winters dry, like salvias, lavender and lemon verbena. Mulching with pebbles can help repel water in winter too.

Although more plant-tags are touting a plant’s drought-tolerance, some clues you can use to tell if a plant is drought-tolerant or xeric are: It has foliage in silver or blue, like lambs' ears, or has hair on the leaves or stems, like a sunflower, which helps grab the water. The leaves may be fat and chubby, like Euphorbia, Sedums or Echeveria (hens-and-chicks); these plants are carrying their own water supply.

The online nursery “High Country Gardens” carries many xeric plants and has a helpful search tool for plants that can hack our soggy winters. Selecting plants that can take 30 to 40 inches of rainfall helped me pick my Agastaches; some strains and cultivars are more likely to melt away.

Portland, Oregon-based Xera Plants (xeraplants.com) doesn’t offer mail order but has a large catalog of xeric plants to browse. The owners also wrote “Gardening in the Pacific Northwest,” which is tailor-made for our conditions.

As the website points out, the Pacific Northwest gets only one quarter of its annual rainfall during the growing season, so trying to emulate the lush summer landscapes of the Northeast United States or England is expensive for both us and the planet. So, as the planet heats up and water becomes scarcer, it makes good economic and environmental sense to pick plants that relish hot, dry summers. Just remember to water those first two years.

— Erica Browne Grivas is a gardener and writer who lives in Seattle.