Once my first hugelkultur bed was up and running, I decided to try building a cluster. With two or more above-ground beds, you can create microclimates in between for lettuces and other plants that don't prefer the heat of summer, while reserving the southwest facing sides for heat-loving plants.
These beds were a lot smaller than the original lone bed, standing at around 2.5 feet tall. I didn't have a lot of wood to work with, but I made them as large as I could at the time. In the above photo you see the first pile in the cluster, which was made from small diameter wood, from small sticks up to pieces around 4" in diameter: saskatoon, rotten pine, a little aspen, and a little biochar (partially burned wood). On top and throughout I layered pulled weeds, hay, leaves, manure, etc. It's like a big compost pile with lots of coarse wood mixed in.
If you have weeds to pull that have seed on them, the weeds can make up the first layer, and the seeds will be smothered by the rest of the pile. It's a great way to get rid of unwanted weed seed without having to set them on fire... the slow burn of decomposition... It is important to get every layer wet while you are building it, since decomposition won't happen without moisture.
I covered the beds with a layer of soil, and then black plastic to help bring the internal temperature up. (The lower left is a hay bale I am heating to kill seeds.)
In the above photo you can see the three beds, arranged in roughly a triangle.
Okay, in case you're having a hard time seeing the triangle, I've drawn red lines along the "ridges" of each bed. (Ignore the log in the lower left; it became a fence post later.)
Once they started to produce, you could no longer see the individual beds, as they were prolific and covered with cucumbers, watermelon, peppers, spring-planted garlic, pumpkins, radishes and potatoes. I harvested a large number of green bell peppers off the side of the bed that faced directly southwest. In the middle, I had lettuce in August.
Remember that the soil below these beds was very rocky, very compacted, and extremely low in nutrients and organic matter. It didn't matter one bit.
This is a giant purple radish that we pulled from the above-ground hugelkultur cluster. We do a lot of harvesting after dark simply because life is so full!
We weren't able to grow radishes as well in our in-ground beds because of the condition of the soil. The hugelkultur beds were an easy way to build a rich growing environment without doing a lot of digging or rock sorting.
But, the digging did begin, and along with it the sorting of rocks, just one month after the radish photo was taken...
But that is a story for another day!