I have been interested in the idea of hugelkultur (‘hill culture’ in German) for a while but there is not really much room around here to give it a go. Essentially, growing using hugelkultur is a process whereby logs, branches and twigs are mounded up starting with the largest diameter material on the bottom working up to and finishing with the smaller diameter stuff at the top. The mound is then covered in earth and allowed to breakdown a bit, then planted out with vegetables, herbs or whatever.
The advantages of a hugelkulture approach are that –
- All that woody material absorbs water and holds onto it, making available to the plants over time, hence the techniques is very water efficient.
- As the woody material breaks down it releases nutrients into the soil, increasing soil fertility.
- Due to the fact that the material is hilled up, the hugelkulture bed has good drainage.
- It enables you to use biomass from your site (or gathered off site if you don’t have any at your own site) which might be difficult to use in another way.
A good size to start with when building a hugelkultur bed is two metres long by one metre wide but I really didn’t have that space hanging around in any area where it made sense, but I have read of people making a standard raised bed using hugelkulture techniques and I thought I would give that a go. Thus it is sort of hugelkulture but not really, resulting in the title of this article.
My original intention was to build a third raised bed in the front yard between the two existing ones and in front of the herb spiral, but this would have required buying in the structure to build the sides of the bed. Linda, with inescapable logic, pointed out that it would be better to convert the southern side raised bed which was originally built as a wicking bed but was never successful. It wasn’t successful because it wasn’t tall enough and rather than the water reservoir and growing area being 300mm deep each, they were only 150mm deep. It was an idea I wanted to try which turned out not to be a good one!
To convert it I first needed to remove the current incumbents, being some rhubarb plants, a few shallots and a feverfew plant then dig out the growing medium it contained and toss it onto a tarp so it wouldn’t get away. It took a while with shovel, and hands, to remove it all but it was eventually done. I left the original builders plastic which formed the wicking bed reservoir in place to frustrate any weeds coming up from below, but the shovel made a few cuts in it, guaranteeing drainage.
While digging out the soil from the inside I had loosened a couple of timbers by using the sides as a leverage point for the shovel, bad idea! I inspected all sides and found a few loose timbers so I went around with my drill and some screws to shore up a couple of the corners. All in all the sides were in pretty good nick structurally but a few of the original screws had rusted away to virtually nothing, and with them replaced we were ready to go!
The next trick of course was to fill the woody material that I had into the raised bed. The general rule is to start with the big stuff and then work your way up to the finer material so that is what I did. Most of it had been harvested from the (very vigorous) mulberry tree in our front yard. This material would usually be either left until the following winter for burning or taken off site for composting. In this case I could use it immediately on our own site!
After each layer of material goes in, it should be thoroughly wetted down to ensure that it is soaked through as much as possible to assist the commencement of the biomass breaking down.
Once all of the woody material has been added and wet down there is a need to add some nitrogen. The woody material will commence breaking down but as it does so the bugs doing the breaking will get their carbon from the woody material, but to balance it out will need nitrogen and they get this from the surrounding soil, making unavailable to plants. To counter this I added a few double handfuls of rooster booster, not having any spare chook manure or other high nitrogen material floating around.
Once I had applied the rooster booster, I shovelled back in all the growing material I had removed and then, because the bed was still not full, I added a bag of commercial compost and of potting mix, watering everything down well after addition. In this case the watering down rehydrates the growing medium, but also washes it down into any empty spaces between the woody material, allowing for a more uniform break down and no empty spaces to cause problems for plant roots.
I completed the process by adding a good 50mm – 75mm of sugar cane mulch to act as a…………. mulch!
With the hugel bed complete I replanted the original inhabitants, as well as a stack of Egyptian walking onions given to me by a friend. My original plan was to prune all but two of the leaves off each of the rhubarb plants but I quickly found out that the root loss caused by the removal and replanting meant that the plants were only transpiring enough water to keep one leaf turgid, so I pruned the limp leaf of each plant, leaving one only.
With the bed now complete it is just a case of keeping it moist so the plants can re-establish and the bugs can start to feast on the woody material!
Note: Here is the bed 6 weeks later. It is thriving, although we did get a 400C day a short while back which knocked the rhubarb back somewhat!
