Raise High Your Garden Beds, Growers!
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Rise to the next level of gardening By elevating your growing beds
Question. Dear Mike: We're going to plant our first garden this spring. Because of the poor, rocky quality of our soil we're going to put in raised beds (It's either that or blast with dynamite every time we want to plant radishes!) I already know not to use pressure-treated wood, but what other advice do you have regarding size, depth, layout, etc? Many thanks; I love your show!
- ---Steven in Reading, PA
Mike: In an effort to increase our usable garden area, I just completed construction of a 16 x 4 foot raised planting bed. We plan to use our own compost as a topping, but need a good, economical material to fill the bulk of the beds. Do you have any ideas? Thank you very much.
- ---Evan in Merion PA
Dear Mike: I love the show—your advice to put eggshells in the hole when you plant tomatoes saved my German Johnson's last year! I have had4 new raised beds constructed this year and filled with mushroom soil.While this is pretty cool, the soil seems sort of heavy for what is essentially a container garden. Should I do something to lighten it up?
- ---M.J. in Wallingford, PA,
Hi Mike: I want to build a small raised bed garden for my 90 year-old mother in Wilmington, Delaware. What should I use to construct the sides, how high should they be, and what kind of "dirt" should I fill them with? Thanks,
- ---Ruth, also in Wilmington(where the earth is made of clay!
Question. Let's begin with a little treatise on raised bed basics, direct from the pages of my brand-newbook "Kitchen Garden A to Z" (Abrams publishers; 2004):
Raised beds warm up faster and drain better than flat ground gardens;provide astounding protection against floods; are much easier to weed,and provide your plants with a nice loose, 'friable' earth by creating a visible barrier against the intrusion of soil-compacting feet. Raised beds can be any length, but should always be four feet wide. This provides maximum growing space, while still allowing you to reach the center of the bed from either side without your big feet tramping down in the planting area. The lanes (walking areas) between the beds must be at least two feet wide; this may seem like a waste of space in the Spring, but trust me, it'll be a tight squeeze by Summer.
Map out your design with stakes and string. Use a garden fork or tiller to loosen up the soil in the areas that will become the beds, then shovel soil from the areas that will be your walking lanes up onto the beds until they're six inches to a foot higher than the lanes. Remove and save any big rocks you encounter. Remove and throw away any big clumps of clay; clay soil cannot be improved—it can only be removed.Never step into the beds; always work with your feet outside their nice loose earth.
Unframed Beds: In the French Intensive System, raised beds are allowed to slope naturally to form mounds. These slopes provide 20% extra growing room when you adorn the sides with small plants like alpine strawberries, lettuces, and compact flowers.
Framed: Framing your beds provides a more formal structure and greater protection during floods. You can use pretty much any material except nasty stuff like old railroad ties and pressure treated wood. Among the most popular non-toxic choices are:
- Wood. Cedar, recycled redwood, locust, and Osage orange are all naturally rot- resistant. But many gardeners simply use untreated pine boards or other inexpensive 'regular' wood.These frames will survive for many years, and return their nutrients to the earth when they finally do decay. (And by that time you'll probably want to change the design around anyway.)
- Stone. Many of us are 'blessed' with excellent framing material in the form of all that rock and field stone we had to dig up to have a garden. Instead of hauling this heavy stuff away, use it to frame your beds. It's very attractive—and stone frames can extend your growing season by absorbing heat during sunny Spring& Fall days and radiating it back into the soil they protect at night. Same for cinder blocks—which you could paint to look nice and/or position with their 'holes' at the top and plant small flowers in those holes.
- Plastic & wood composites. Most lumberyards carry at least one brand of faux landscape timbers made from recycled plastic and wood shavings. I used one of the oldest—"Trex"—to frame some of my beds a good decade ago, and the timbers show no sign of age(I wish I could say the same!). These products look like wood, can be worked like wood, and will last virtually forever. (See sites like www.trex.com for more info.)
I like to use half garden soil (you'll be lucky to have that much left after you toss all those giant clods of clay) and half mushroom soil or other high-quality compost to fill my beds. Such composts are widely available in bulk, and provide all the food your plants will need this season—maybe for several seasons. M. J.: That compost may seem heavy, but it's a heck of a lot lighter than the nasty clay so many of us are cursed with. But go ahead and lighten it up; you'll only make a good thing better! Buy big bags of perlite and/or vermiculite and mix some of these natural mined soil-lightening materials into your beds. (Just like Mel Bartholomew says in the classic "Square Foot Gardening"!)
And finally, Ruth: At 90 years young, your mom should be done with bending over. Build nice, tall, two to three-foot high platforms for most of her raised beds. Fill the bottoms with rocks—they'll make for great drainage—and save the good soil for the top foot or so. Size them so that she can work at 'ground level' while she's sitting down and harvest things like peppers and eggplants when she stands up. Most tomato plants are going to grow to be her size, so plant these in regular raised beds.
You Bet Your Garden Question of the Week ©2005 Mike McGrath