Master Gardeners test drain field plants in Island County

A three-year plan to study and identify which plants with non-invasive root systems are appropriate for planting on drain fields in Island County will soon be moving from the planning to the planting stage at Greenbank Farm.

A group led by Master Gardener Marcia Nelson will have two test drain fields constructed, each 6 feet wide and 20 feet long, along the entry to the Greenbank Farm, adjacent to the caretaker cottage and the southern end of the Master Gardener Educational Display Garden. One will be an in-ground system, the other a mound system. These will simulate actual drainfield conditions.

Over a three-year period, various plants suitable to the Whidbey Island climate and soil and moisture conditions will be tested on the two mock drain fields that represent the most common types used on the island. At the end of the test period, the plants will be partially dug out in order to measure the depth of their roots. This will determine which plants have infiltrated the distribution system.

Plants to be tested have been selected by Master Gardeners with the advice of Dr. Carol Miles, WSU Northwest Washington Research and Extension Center, from a list of plants already being used by Island County Master Gardeners on their drain fields. The Whidbey Island Garden Tour has donated $1,300 toward the purchase of the selected plants.

A holding tank filled with water and liquid fertilizer will stand in for the normal effluent found in a drain field and the system flow will be metered by a computerized controller. Jerry Stonebridge of Stonebridge Environmental Construction in Freeland is donating his labor and design expertise to the project. Construction materials have been donated by Krieg Construction, Norwest Concrete and Mailliard’s Landing Nursery, all of Oak Harbor, as well as Orenco Systems, Sutherlin, Ore. and HD Fowler of Bellingham.

The goal at the end of three years is to publish a brochure to be made available on the Island County WSU website and to be circulated by the Island County Department of Health and Planning Board, septic system installers, nurseries and Island County Master Gardeners. The brochure will advocate the best plants for use in drain fields.


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