MASTER GARDENER PROGRAM — MGs in the News
Published in: The Columbian • March 17, 2016, 6:01 AM
By Pat Stephens and Judi Seifert, for The Columbian
Raised beds have some great advantages over in-ground gardens:
- They provide great drainage, especially needed with our heavy, clay soils, which tend to hold water very strongly.
- The soil in a raised bed warms earlier in the spring and stays warmer later in the fall.
- The higher beds are easy to access for those with back or mobility problems.
- Weeds and pests can be easier to control.
- They can enhance the beauty garden.
- A raised bed can be covered in winter, providing an opportunity to grow some cool weather crops for all-winter use.
- Poor native soil can be enriched only where necessary.
- Irrigation and fertilization needs are limited to the raised beds and not the surrounding pathways.
Gardeners have several options for growing in raised beds. For mounded rows, scoop the native soil out of surrounding areas, creating lower paths that can be covered with mulch or chips for walking. Then add compost to the native soil to enrich it with nutrients and create a better soil structure to improve water movement.
Layered composting is another way to create raised beds, and can be done right on top of existing turf with no digging. First lay down a thick layer of wet newspaper or cardboard in the shape of the desired raised bed. Then lay down a 3-inch layer of green matter, such as leaves, grass clippings or aged manure. Top this with a 3-inch layer of brown matter, such as dried leaves or shredded newspaper. You can alternate several layers if you want a higher bed. Add a 3-inch layer of enriched garden soil on the top and you are ready to plant. The lower layers will break down and compost in place, creating a rich growing medium for seasons to come.
Filling a framed bed takes significant quantities of soil. Purchase a garden mix from a local nursery or garden center. Mixes typically include clay, sand and an organic material such as compost, often in a 1-1-1 ration. These proportions allow water to move easily through the soil, and the organic matter holds nutrients well. Mix in some native soil from the surrounding beds to make a well-rounded planting medium for our region.
Often in the Pacific Northwest, additional nitrogen is needed to help organic matter break down, so add a commercial nitrogen fertilizer broadcast over the raised bed. Because raised beds drain well, additional nutrients may be needed during the growing season.
The looser organic soil in raised beds will be warmer and will dry out faster than clay ground soil, so set up a good irrigation schedule. Soaker hoses or drip systems will provide effective irrigation to the root systems of the plants without drenching the leaves.
If you have raised beds from previous years, you may notice that the soil has settled. Simply replenish with fresh organic matter or compost each spring, and spade up the soil to work it in before planting.
Anyone can enjoy raised beds and the increased yield of vegetables and fruits from the garden.
To Learn More:
- www.gardening.cornell.edu/factsheets/vegetables/raisedbeds.pdf
- http://cru.cahe.wsu.edu/CEPublications/FS075E/FS075E.pdf
- https://catalog.extension.oregonstate.edu/fs270
Pat Stephens and Judi Seifert are Master Gardeners with WSU Extension Clark County