How do I make SOIL for my raised beds?
-Jo in Asheville
I don’t have much first-hand experience with raised beds, because my gardens have always been planted directly in the ground. However, raised beds are the preferred growing method for multitudes of gardeners and I think they are a great way to garden. Because the bed is raised, you have much greater control over the soil tilth and you can enjoy light soil almost immediately. You have various options for making soil for your raised beds.
Many local gardeners like to use Mel Bartholomew’s Square Foot Gardening Mix.
Mix this recipe together thoroughly:
1 part – peat moss (Peat moss doubles in size once wet: 1 CF = 2CF once it is wet.)
1 part – coarse vermiculite (use coarse, not medium)
1 part – five different kinds of compost
Calculate the amount of mix you need by multiplying length x width x height (for instance 4’ x 8’ x .5’ (6 inches) = 16 cubic feet of soil).
Compost suggestions: These are mostly bagged composts – composted cow manure, composted chicken manure, mushroom compost, vermicompost (worm castings), McEnroe compost, other high quality compost, and your own backyard compost. Real compost has heated up enough to kill the pathogens and weed seeds. A pile that is slowly decomposing in the corner of your yard probably has not heated up enough to kill unwanted weed seeds. I don’t recommend adding cold compost to your raised garden beds because of the potential for introducing weeds and pathogens. Super-cheap brands of bagged compost should be avoided. Opt for the best quality compost that you can find. Local garden centers have different types of good composts available. Bulk compost is available at some local mulch yards, but bulk compost is an impractical expenditure for only one raised bed. Again, look for best quality compost and each year add more compost to reinvigorate your raised bed’s soil.
Because Mel’s Mix is very fluffy and soft, it is easy to weed and easy to plant. I have heard many reports from gardeners who are very happy with this mix and the rest of Mel Bartholomew’s Square Foot Garden plan. Check out more about Mel’s method here.
According to UAF Cooperative Extension Service, add about 3.5 pounds of lime to a 4×8 garden bed that has never been limed. Proper pH makes all the difference, and lime is especially important when you are using peat moss which is naturally acidic.
At the opposite end of the spectrum, this is a cost effective and simple approach: simply mix generous amounts of compost (up to 50%) with the native soil in your yard, and fill your beds with that mix. Don’t expect this mix to be soft, fluffy, or weed free. It will be much heavier that “Mel’s Mix”, but you can still grow a great garden in this soil. Be sure to weed any soil well before adding it to your garden bed.
You can also combine various aspects of both of these ideas, but just remember that regular topsoil is much heavier. Think twice about buying bagged topsoil and consider the source. Super cheap “topsoil” can be really, really bad. You have topsoil in your yard at no cost and it may be better soil than what is available in bags. If you want to enjoy fluffy soil, skipping the topsoil may be a good idea. Some people use organic potting soil to fill their raised beds, but quality potting soil will be a pricey option. Whatever you choose to do, you can improve your soil with cover crops in the summer and fall, with annual additions of compost, and with lime applications when recommended by a soil test.
- Raised beds usually have better drainage than a garden that is planted directly in the ground, but that also means that raised beds dry out more quickly. This is an advantage in the spring when the ground is cold and wet, as raised beds can often be planted earlier in the season than regular gardens. It is a disadvantage during a summer drought when every ounce of water counts.
2.Peat Moss is considered a limited resource and some folks think it should not be harvested at all. It also sequesters carbon – an important consideration as we face climate change issues.
Hope this helps, Jo!
Thanks for writing,
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Ruth Gonzalez is a former market farmer, gardener, and local food advocate and blogger at http://tailgatemarketfanclub.wordpress.com. In her job at Reems Creek Nursery, Ruth offers advice on all sorts of gardening questions, and benefits daily from the wisdom of local gardeners.
Ask Ruth © 2015 Ruth Gonzalez & Organic Growers School
Ruth Gonzalez is a former market farmer, gardener, and local food advocate who wants to see organic farms proliferate and organic gardens in every yard. She serves on the Organic Growers School Board of Directors, and in her job at Reems Creek Nursery, Ruth offers advice on all sorts of gardening questions, and benefits daily from the wisdom of local gardeners.