Saturday, May 02, 2009
Terraced Garden with Raised Beds
While lots of plants do well on steep slopes, most vegetables do not. Vegetables need rich, loose and deep soil, which washes away and falls away on steep slopes.
Our street in Augusta, Maine goes up and down a long steep river valley. Each house lot is terraced like a staircase. A seven foot high earthen berm separates our house from the house above us and the house below us.
The challenge is how to use these steep earthen berms for vegetable gardening. Our solution is to make terraced gardens with raised beds.
The three raised beds in the top photo are built with eight foot long 2 x 12s for the front plates and stacked 4 x 4s for the sides. Construction details are here. Each bed goes about four feet deep into the slope. The front and sides are secured with pointed 2 x 4s driven about a foot into the soil. Keeping all the dimensions plumb and level is not important to the plants, but makes the whole thing look better.
Filling the 12 inch deep raised beds with soil is easy. Chisel into the berm with a shovel and drag the soil with an iron rake into the raised bed until you fill it. This creates a level planting and growing surface where there used to be a steep slope. If you can, supplement this soil with the best compost you can get and mix it all in.
The advantages of raised beds are numerous, but in our central Maine climate, they are essential to growing heat loving, long season plants like peppers and heirloom tomatoes.
Raised beds help keep the soil temperature higher in the spring and early summer, which tomatoes and peppers need, and keep the soil around the roots from becoming waterlogged. Building raised beds is like building hills for corn, which the Wampanoag Indians in Massachusetts helped to invent. During the spring and early summer, a hill of heaped soil will get warmer in the day and stay warmer at night compared to the flat dirt around it. This is critical for germination and early growth of corn, but also tomatoes and peppers, which really need warm soil.
The secret to a terraced, raised bed garden is to fill the beds with the best soil you can get. We use free leaf compost from the City of Augusta, Maine's recycling facility up the street. We call it "the dump." If your town or city does not recycle leaves and let people use them as compost you should ask them to start doing it. It's the key in the lock.
Also, because you walk around the raised beds, not on and in them, the soil does not become compacted and the developing root systems are not crushed by your footfalls. As I learned from my dad, the most important part of a plant is underneath your feet.
Here are the raised terrace beds from the viewpoint of the giant silver maple tree in our yard, May 2009.