Bellevue’s Waterwise Garden is a living showcase of planting ideas to cope with climate change

RIGHT ABOUT THIS time last year, the Puget Sound region experienced a “heat dome event,” when temperatures soared to record highs and stayed there for days. While heat is perhaps the most obvious marker of our changing climate, its meteorological twin, drought, presents challenges in the garden even when temps remain moderate.

It’s time to rethink landscape goals and planting strategies to accommodate what’s quickly becoming our new normal.

Jil and Howard Stenn are committed to creating beautiful gardens that conserve soil and water resources. For 30 years, Stenn Design, their landscape design and consulting firm, has tended the Waterwise Garden at Bellevue Botanical Garden (12001 Main St. in Bellevue) from design to its present maturity. Sponsored by Bellevue Utilities, the Waterwise Garden is a living laboratory and public demonstration landscape filled with planting ideas and garden practices that are inspiring and informing.

The Waterwise Garden was designed to present several growing conditions approached from the perspective of water conservation and efficiency. Planting beds basking in full sun are brimming with flowering perennials, like wand flower (Dierama pulcherrium), several hardy geraniums, Jerusalem sage (Phlomis fruticosa) and beeblossom (Gaura lindheimeri). The plants bloom throughout the dry season with little additional summer water, contradicting the idea that a waterwise garden is weak on flowers. “We’re dispelling the myth that [a drought-tolerant garden] is all lava rock and juniper,” Jil remarks. “It can be a really lush garden.”

Nearby, a kitchen garden produces bountiful crops of vegetables, herbs and fruit utilizing an efficient drip irrigation system, and it benefits from regular applications of compost and mulch. These are the perfect conditions to tuck in what Jil calls “juicy annuals,” seasonal plants that need supplemental water to thrive during the dry months. “It’s all about zoning your garden and grouping plants by water use,” she observes.

Beneath a stand of mature firs and deciduous trees, hardy shrubs such as purple barberry (Berberis thunbergii), golden Mexican orange (Choisya ternata) and oakleaf hydrangea (Hydrangea quercifolia) thrive despite root competition, forming a matrix of colorful foliage and seasonal bloom. Mixed in with the woodland planting, hardy fuchsias are a shade-loving, surprisingly satisfying shrub that blooms all summer. Textural ferns and grasses mingled with resilient groundcovers carpet the ground.

In addition to selecting the appropriate plants, Howard, the expert soil and water guy of the design duo, recommends proper soil preparation, a generous layer of mulch and attentiveness when it comes to watering.

Stenn Design has produced numerous online resources to guide gardeners through every step of the process. Visit the Bellevue Botanical Garden Waterwise Garden website to access a library of Natural Garden Resources.

While discussing the lasting effects of our recently wonky weather, Howard advises, “Established plants that have never needed much in the way of supplemental water may need deep watering a few times this summer to build back from damage inflicted over the past year.”

Even if you rely on an irrigation system, it’s a good idea to dig a few test holes in various parts of your garden to evaluate soil moisture. Light or infrequent irrigation might permeate the top few inches, yet leave the deeper root zone parched.

Considering the long view, the Stenns are fans of fall planting to take advantage of seasonal (and free) rainfall. And as to what to plant, think trees. Not only do trees lend structure and dynamic seasonal interest to the landscape, but in time they will provide precious shade. “Be strategic,” Howard advises. “Partial shade tempers the climate, provides a little bit of frost protection and cuts water usage.”

If you’re ready for some relief from hot, dry conditions, the Waterwise Garden is well worth exploring in person.