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Energy Adviser: Soil content critical for native plants

Tests can show alkalinity, acidity, plus nutrient value

The Columbian
Published: March 23, 2017, 6:00am

It’s tough to draw a line in the dirt and say plants before this date are natives and those after it aren’t. There is no exact date that defines what a Pacific Northwest native plant is.

If you need a rough dividing line, it falls somewhere after 1824, when David Douglas explored and cataloged plants of the area for the London Horticultural Society, and before 1836 when immigrant wagon trains first rolled west.

“Once the Oregon Trail opened, settlers brought all kinds of seeds,” said Julie Carlson, master gardener and volunteer at NatureScaping in Brush Prairie. “Washington is known for apples, but the settlers carried apple seeds and planted them here.”

Nearly 200 years later, some of these newer arrivals have become invasive, such as Japanese knotweed, Scot’s broom, and Himalayan blackberries that easily overtake native habitats.

“Native plants evolved to attract native wildlife and wildlife has adapted to native plants,” Carlson said. “That’s especially true of pollinating insects.”

This makes them better suited to the area. Wildlife and pollinators have a long history of mutual interaction with native plants. They also have adapted to our wet winters and dry summers and repel harmful insects, organisms and diseases better than non-natives, and are suited for our soil.

While there are 3,000 plants native to Western Washington, fewer than 300 or so are suitable for residential use, according to the Washington Native Plant Society website, http://www.wnps.org, where you can find descriptions of many species. Other places to research are the WSU Master Gardener Program, and local nurseries selling native plants. Searching wsu.edu also turns up information on native plants for our area.

Once established, native plants need less water, fertilizer, and pesticide than non-natives do. According to the EPA, homeowners apply 20 times more chemicals an acre than farmers. Planting natives reduces the chemicals flowing into groundwater and makes yards safer for kids and pets.

Placing native plants in the right location with the right soil is important to their success, Carlson said. Homeowners planning to make a significant investment in landscaping with native plants should have their soil tested to find if it meets the needs of the plant. “Too often, housing projects scrape much of the soil off leaving mostly clay,” she said. “Knowing what’s in your soil is the first step toward establishing natives around you home.”

Soil tests show the acidity or alkalinity (pH) of your dirt, as well as its nutrient value. Washington State University Extension recommends a Portland company, A&L Western Agricultural Laboratories. According to its website, A&L charges $36 for a test and report including recommendations and graphic charts. Recommendations may include how to bring the pH of your soil to the level needed for natives.

For properties with multiple micro-cultures, wet and shady, or sunny and dry, more than one soil test may be needed. The test results can help DIY landscapers and gardeners know where to put their plants. “I cannot say too often ‘put the right plant in the right place,’ ” Carlson said. “A moisture and shade-loving native won’t do well in the sun no matter how much you water it.”

Native plants can also save energy. Planting native trees and plants strategically can cut your home’s energy use. A well-planned landscape can reduce the summer air-conditioning costs between 15 percent and 50 percent for an unshaded home, according to the Department of Energy’s National Renewable Energy Laboratory.

“The key to native plants’ success is finding an environment where they will thrive — and using lots of compost,” Carlson said.

For more ideas related to landscaping and home improvement, mark your calendar for the annual Clark Public Utilities Home & Garden Idea Fair, April 28 to 30. Details at www.homeandgardenideafair.com.


Energy Adviser is written by Clark Public Utilities. Send questions to ecod@clarkpud.com or to Energy Adviser, c/o Clark Public Utilities, P.O. Box 8900, Vancouver, WA 98668.

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