Keep Your Garden Cool When It’s Hot

August 9, 2017 5:52am

A host of drought-tolerant perennials and shrubs, including daylily, shasta daily, artemesia, and rosemary on our south-facing sandy slope. Image: E. Grivas

Despite Seattle’s soggy reputation, any gardener here knows our summers are dry. Dry as toast.

But first comes winter. In winter, winter rains flood plants. If they survive that, which many tough customers didn’t in last winter’s record pelting, then – just as the growing season gets underway, as plants send out their tender feeder roots, the rain vanishes until September. What kind of a cruel joke is that?

This cycle causes a lot of death and heartache in the garden, closely followed by ballooning water bills for the gardener. To save time and money, keeping you and your plants happy, here are some tips to help drought-proof your garden.

White Echinacea (coneflower), yellow Achillea (yarrow), and red Helianthemum make a waterwise trio in my yard. Image: E. Grivas

Choose the right plants:

Find plants that prefer summers on the drier side. Many Mediterranean plants fall into this category: lavender, rosemary, and sage, as well as plants that evolved on prairies and grasslands: coneflower (Echinacea sp.), sunflower (Helianthus), many ornamental grasses, and black-eyed Susan (Rudbeckia). Succulents, like sedums and Hens-and-chicks (Echeverias), whose leaves hold their own water reserves, are a great choice.

Alpine or rock garden plants have shallow roots and tend to like the excellent drainage offered on shallow, gravelly slopes. These are usually found in the “sunny groundcover” section of the nursery. Some examples are Lithodora, Cerastium, and creeping thyme.

Go for the silver:

Having silver and/or furry leaves helps a plant conserve moisture – in addition to being cool-looking, these tend to be drought-tolerant: Lambs’ ears (Stachys), Artemesia, and Phlomis.

Lay groundwork:

Amend your soil with compost in each planting hole and as a top dressing annually. Compost brings your soil structure into balance; it will help clay soils drain or sandy soils hold water.  Good winter drainage is crucial for many waterwise perennials that hate “wet feet” in winter, like Echinacea, Agastache, and succulents.

Cover up:

Topping with mulch like gravel or bark chips will hold moisture in any kind of soil. Or, for extra garden points, you can plant a living mulch of groundcover plants.

All the tough yellows: Sunflowers and Rudbeckias at Ravenna Gardens.
Image: E. Grivas

Water wisely:

No matter how “drought-tolerant” a plant is, it still needs water during those crucial first two seasons to establish a good root system. Plants in containers need water more often – sometimes as much as twice a day if temperatures are over 90.

The ideal time to water is early in the morning to let leaves dry before the sun turns on the heat. However, if your plant is wilting, water it!

Watering at the base of the plants with drip irrigation, soaker hoses, or ollas (irrigation pots used for small areas), is much more efficient than sprinklers which allow a lot of water to evaporate and can foster leaf issues. Long, deep watering less frequently grows strong roots; frequent shallow watering encourages weak shallow roots.

Going on vacation? Hopefully you have a system, or helpful neighbor in place. Here’s a tip for your potted plants, which are the most vulnerable- give them a vacay too – in the shade. They’ll last longer between waterings.

For more plant ideas:

Great Plant Picks drought-tolerant plants for sun.

Swanson’s Nursery scroll to “Waterwise Gardening” for several lists.

Sky Nursery’s lists