Ah, the Germans, a lovely people with a lovely language. For example, did you know the German word for daisy is "gänseblümchen?" It just rolls off the tongue. The Germans created a method of gardening in which they cultivated plants on top of a constructed mound made up of logs buried in the earth. They call it hügelkultur - literally mound or hill culture. The theory is that as the logs decay, they provide nutrients to the plants growing on top of them. In addition, the mound shape provides a sort of natural rain drainage. Plants on the top that need less water get less, and those nearer the bottom get more water. You can also use the hill shape to vary sunlight. Plants on the sunny side get more light; plants on the opposite side a bit less. Finally, the hill itself is supposed to provide a bit more growing space. Imagine the mound as half of a sphere. If the mound was not there, you would be planting in a circle with an area based on the diameter of the sphere. But with the mound, you have a planting area half the surface of the whole sphere. Assuming a mound with a 10-ft. diameter, you are roughly doubling your growing space (if I did the math correctly).
Above is our first try at hügelkulture, as it stands today. We decided to make it an herb mound. It could just as well support other plants, but an herb mound is a common choice. As you can see, we did all right. We have good growth from the sage in the foreground, the marjoram at the top, and the grey santolina to the right of the marjoram. There are also a couple of young oregano plants tucked between the sage and marjoram. Not shown: the reddening lepiota mushrooms, which grew prolifically all over the yard including on the mound - delicious! More about them in this post here. Herbs that did not make it on the mound (this year) were all sown as seeds, a tough go for non-native perennials, especially here in the beginning before the logs beneath the earth had a chance to decay.
How do you make one of these mounds? I'm sure you are thinking it requires elaborate planning, detailed construction, and a great number of resource inputs. Or maybe you're looking at it and thinking, "It's a hill; how tough can it be?"
If you have read about my squash tunnel here, and its tragic demise here, then you know I am a big believer in scavenging for resources. Fortunately, we live in the Midwest, where the same storms that brought down the squash tunnel regularly bring down trees in the neighborhood. And when workers are cutting up those trees, they are usually very happy to have you help them out by hauling off some of the debris. That's how we got the logs for the base of our hügelkulture.
We took some of the logs and arranged them in a circle with the diameter we wanted for the mound.
Then we buried them and placed more logs on top. Repeat this process until you have a mound - easy peasy!
Once we had the mound shape, we covered it in cardboard, a layer of mulch, and planted herb starts. As I said, they did pretty well. But in theory each year that goes by, they should do better and better. The buried logs will decay and provide nutrients to the planted herbs. The first year the logs barely had time to start the decay process so the herbs were more or less relying on the soil covering. After this winter, the logs should be breaking down nicely, and I hope we will see a much more robust hügelkultur herb mound next spring and summer.