I’ve written before about my experiments in hugelkultur — building raised beds with rotting wood and other materials. I should now explain some of the rationale for this continuing effort. Due to the wet climate and a chronically high water table, the lower part of my garden has been plagued with two problems: compacted, waterlogged soil, and the prevalence of weeds such as slender rush—a plant that grows from rhizomes deep in the soil and is nearly impossible to get rid of. So for me, raised beds are a necessity.
Fortunately, another Scott County gardener, Anna Hess, has encountered a similar problem. In her book "The Ultimate Guide to Soil: The Real Dirt on Cultivating Crops, Compost, and a Healthier Home," Anna describes one method she has used to combat waterlogged soil. Drawing on the example of Central American chinampas, she digs trenches around the beds, piling the soil from the trenches on top of the existing soil, while allowing the water to fill the trenches. I decided to try this with one of my problem beds, along with a new hugelkultur mound that I started last year, as illustrated below.
My plan was to seed the beds with mammoth red clover, which is supposed to aid in breaking up compacted soil, as well as supplying nitrogen. But initially I made a fatal error. I dug quite a bit of soil out of a drainage ditch that had become blocked where the water runs down out of the ravine, and I thought this would be a great source of topsoil for building my raised beds. Boy was I wrong! Only after adding the soil I realized what I had added was pure silt—a material that dried to a hard crust without a speck of organic matter in it.
Nevertheless, I attempted to pound some clover seed into this material and watered it several times a day, only to have a small amount of clover germinate, then die when I inadvertently let the soil dry out. That was when I hatched the plan to dig the chinampas, adding the soil from the ditches. This waterlogged, compacted soil was only slightly better than the silt from the ravine, but this time I also added an inch or two of almost-finished compost. I had already used up most of my mammoth red clover, but I took what was left, mixed it with crimson clover and buckwheat and reseeded the beds.
The germination was still very spotty in the hugelkultur mound, but the other bed is greening up nicely with the buckwheat, and I can see little clover seedlings in the shade of the buckwheat.
Another of my chronically waterlogged plots will become a lasagna bed for potatoes next year, after resting under a kill mulch this season. One strategy that I believe has helped here was planting water-loving boneset on the downhill side of this bed, which has grown spectacularly.
And the last, very large problem bed, where an entire planting of seed potatoes rotted last year, will become my next hugelkultur project.