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Coronavirus COVID-19

COVID-19 Advisory: WSU Extension is working to keep our communities safe. All Extension programming is being provided virtually, postponed, or canceled. Effective March 16, 2020, WSU Extension county offices and WSU Research & Extension Centers will be closed to the public. We are available via email, phone, and webconference.

The Drainfield (Toto) Garden

Program Contact: Loren Imes
(360) 639-6059 •

The Drainfield Garden (nicknamed the Toto Garden) was originally established as an experimental garden to test the root invasiveness of plants that were commonly recommended for growing on a drainfield. Master Gardener Marcia Nelson started the project to test the assumption that selected plants had non-invasive roots, using a mock drainfield.

A mound is a type of drainfield that is installed when the ground does not percolate at required county standards. The mound in the drainfield garden is evolving to display plantings that consider current knowledge of best practices for plants to use in drainfields.

General guidelines for drainfields:

  • No playgrounds, patios, irrigation systems, or mulch, since these interfere with septic evaporation. Playgrounds compact the soil.
  • No trees or large shrubs, since large root systems will interfere with conduits. Beware of trees planted close to or within the drip line of a drainfield.
  • No edible plants, since fruits, berries, herbs, and vegetables require too much water and tilling. Also, plants on drainfields may be contaminated with harmful organisms.
  • Use gloves whenever working with soil or plants on a drainfield.


The following free downloads provide useful information about best practices for drainfield planting: