Seattle’s hotter summers call for drought-tolerant landscaping
Typically, June is still a foggy month in Seattle, which helps plants survive the area’s typical dry season from July to September. But these months of June have not happened for several years, and this year has shown that our dry season can become very to dry.
And the trend is expected to continue.
“We expect warmer weather and more drought” in the Pacific Northwest, says Kate Kurtz, Seattle Public Serviceplanner for the conservation of organic matter and landscape resources. To combat future climate change, she recommends changing your approach to your home’s landscape.
“Look at your plants now,” Kurtz says. “He’s the most stressed they’re going to be, at the end of the summer.”
If your garden is currently a crime scene of dead and dying plants, investigate the causes and prepare to take a more drought tolerant approach.
The root of the problem
To make a change, start with the ground. Healthy soil will hold more water, whether it’s a passing rain or your garden hose. A healthy base will act like a sponge, Kurtz says, preventing plants from drying out.
She says future precipitation could take the form of severe thunderstorms rather than the typical Seattle fine mist. Poor soil sends pollutant-carrying water to drains, streams and Puget Sound, affecting regional water quality. But since most Seattle properties are privately owned, homeowners who create landscapes that are water and climate friendly can mitigate the effects of this runoff.
To improve the health of your soil, Kurtz suggests adding nutrients by mixing 2 to 3 inches of compost into the existing soil. For lawns, rake about a quarter of an inch of compost in the grass each year. Every few years, add a few inches of compost around the base of perennials, shrubs, and other established landscaping.
Soil amended with compost will also be teeming with healthy microorganisms, which help defend against plant pathogens, viruses, and fungi. Plants with depleted soil systems may more easily fall prey to such threats.
Maintaining healthy soil and plants can also reduce the need for pesticides and herbicides, even “natural” or “organic” formulations, which can still kill beneficial insects, Kurtz explains.
Attracting and keeping beneficial insects in your garden can be one of the best defenses against insects that you don’t want. For example, ladybugs and lacewings feed on aphids, mealybugs and mites. The yellow vests try to eat your meat on the barbecue because they are carnivorous and, therefore, they also devour many garden pests.
Climate change will also have an impact on our approach to watering. Maintaining a strong, well-hydrated root system will increase the resilience of your plants during droughts, says Kurtz.
Established plants, trees and shrubs only need occasional watering, even in very dry and hot summers like this. Run a garden hose about 30 to 40 minutes a week to deeply water a plant’s root system; this can vary depending on the plant and the type of soil.
Then check your work. An hour after watering, use a trowel to dig 6 to 12 inches and see if the soil is moist throughout the root zone of a plant.
Laura Matter, Sustainable Yard and Home Education Program Director at Tilth Alliance, claims that many homeowners struggling with dry and dying gardens this summer have contacted the Seattle nonprofit helpline at 206-633-0224 or gardenhotline.org to help.
She says the staff of horticulturalists and professional educators tell callers that preparation and prevention are key to keeping your garden alive this year and thriving in the future.
If a heat wave is forecast, for example, Matter suggests watering the day before peak temperatures. If some plants have already sunburned (turning white), cover them with shade cloth or move them to covered areas before the hottest days.
Adding mulch around trees and shrubs helps them retain water by reducing evaporation. The mulch also acts as an insulation so the soil doesn’t get as hot, says Matter.
As for lawns, even if your grass hasn’t been green in months, don’t give up right away.
“Lawns get a bad rap,” says Kurtz. Often thought of as ponds of water requiring high levels of maintenance, lawns can be made greener by mixing together drought tolerant species such as clover and blue star creeper.
It’s fine to let your lawn “turn golden” in the summer, says Kurtz. Water it once a month and try to avoid using the area heavily, or you might find that it won’t turn green again when the rains return.
Plants for a new climate
If a plant hasn’t been successful this year, don’t replace it with the same species, Kurtz says. Now is the time to look for more heat and drought resistant options. The material suggests drought tolerant plants such as California lilac (ceanothus), shrub cinquefoil (cinquefoil), cistus (cistus), hebe and shrub lavender and rosemary.
Seattle residents can look to the drier parts of Oregon and northern California to find species that could thrive here. For example, Kurtz says that an incense cedar (Calocedrus decurrens), more common at higher elevations, might adapt better to a drier climate than a western red cedar that is thirsty for water.
Near Carnation, a pilot project is experimenting with reforestation using native trees, such as Douglas firs and other conifers, which have adapted to the drier conditions of southern Oregon. If they are successful, expect these trees and plants to start showing up in local nurseries, Matter says.
“Native plants are more suited to this region, which gives them a good chance of success,” says Kurtz.
Matter’s native recommendations include sea spray, red flowering currants, and dogwoods. Native grass seeds will not need as much water and may grow a little taller; mix wildflowers for beauty.
But even drought tolerant greenery needs extra care while establishing itself. For trees, use a donut-shaped watering bag and fill it twice a week from May to September. Or water for 20 minutes with a small stream of a garden hose at the base of the tree.
Most garden centers have knowledgeable buyers and sellers who can help you find the right plant for the right location in your garden, depending on slope, shade, sun, and other variables. Some homes in the Seattle area have swampy backyards, while others can be hot and dry.
This year has been a great learning opportunity for gardeners, says Kurtz, as we can expect drier summers, more heat domes, and drier soil in the future.
“Look what failed [to grow], and ask what you can do differently, but don’t give up, ”she says. “Our trees, soils and landscapes are a shared natural resource that has the potential to impact our entire community, as is the quality of our air and water.”
Resources for gardeners
Municipal and regional programs can help you prepare for the impacts of climate change on our yards and gardens – and mitigate those impacts overall. For example, that of Seattle Trees for neighborhoods The free trees in the program provide you with shade while extracting additional carbon from the atmosphere and reducing the intensity of urban “heat islands”.
Here are several other resources with information on native plant choices, soil amendment, effective watering and more.
INDIGENOUS PLAN RECOMMENDATIONS
• King County: kingcounty.gov/gonative
• Washington Native Plant Society: wnps.org/native-gardening/resources#habitat
SPECIAL EVENTS AND OFFERS
• A free compost gift: seattle.gov/utilities/your-services/collection-and-disposal/recycling/beyond-the-cart
• Watering timer discount: seattle.gov/utilities/protecting-our-environment/sustainability-tips/conserve-water/for-residents
• Calculate how much compost your soil needs: savewater.org/lawn-garden/soil-mulch-compost-fertilizers/compost-mulch-calculator
• Addition of rain gardens and cisterns: 700milliongallons.org/rainwise