After building four raised veggie beds in my backyard, I baulked at buying in loads of costly soil and compost to fill them.
Instead, I opted for a thriftier route — and filled them up for free using rotting logs and old branches.
It's called 'hügelkultur' (pronounced 'hoo-gul-culture'), a no-dig layering method often used in permaculture food gardens to create self-sustaining beds.
Six months on and my hügelkultur raised beds are pumping out the most plentiful summer harvest I've ever grown.
What is hügelkultur?
Devised in Austria centuries ago, hügelkultur involves stacking piles of old wood and other garden prunings into a soil-covered mound, creating raised beds that purportedly 'take care of themselves'.
The wood acts like a sponge over time, helping reduce the need for watering, while also slowly releasing nutrients to feed your veggies for years to come.
Adaptions for an Australian climate
In cool and wet European climes, hügelkultur (which roughly translates to 'hill culture') usually involves building steep mounds about one metre high, creating extra surface area to plant into on the top and sides of the bed.
But for me here in hot and dry Tarntanya/Adelaide, that large surface area would be problematic, as evaporation occurs more quickly when soil is exposed to air. So, a steeply mounded bed would dry out too quickly and require too much extra watering.
Instead, I sourced lengths of salvaged jarrah timber and, with the help of friends, built enclosed frames for low raised beds to a height of 33 centimetres from the ground. But hügelkultur works well in raised beds of any size in Australia, and within in-ground trenches, too.
Materials needed for hügelkultur layers
In the months leading up to building my raised beds, I purposefully kept a heap of material I'd normally place in my council kerbside green bin – aged logs (hardwoods are best), decaying and dead branches, sticks and fruit tree prunings.
On the day, I also trimmed and pruned my hedges, ground covers, annual herbs and anything else I could find, to create a pile of nitrogen-rich 'green' materials I could layer into my hügelkultur beds. Other useful greens include weed-free lawn clippings, seaweed and food scraps.
I made sure I had plenty of compost on hand (mine is homemade, but store-bought organic compost is fine, too), plus nitrogen-rich fertilisers — I used a combination of aged chook poo and a store-bought certified organic fertiliser.
'Brown' carbon-rich materials are needed for the hügelkultur layers too — I sourced shredded paper free from a local office. Dried leaves and straw are other good options.
How to create a hügelkultur bed
With my materials collected, it was time to get building. These are the steps to creating hügelkultur layers:
- 1.Place a thick layer of cardboard in the bottom of the bed, to help prevent weed growth.
- 2.Pile woody material in first, starting with the largest logs and gradually layering smaller branches and sticks on top until about a third of the raised bed is full. Water well.
- 3.Add a nitrogen-rich layer directly on top of the wood, such as aged manure, grass clippings or compost — this can help counteract nitrogen deficiencies in the early stages of log decomposition.
- 4.Next, follow the no-dig gardening system and alternate carbon-rich 'brown' materials with nitrogen-rich 'green' materials in lasagne-like layers to fill another third of the bed, watering well between each layer. In my beds, I repeated the following three layers: green garden prunings and compost, then shredded paper, then organic fertiliser. Importantly, I made sure to fill in gaps around the logs and wood material, to prevent air pockets that would dry everything out.
- 5.Lastly, to fill the top third of the bed, add a thick layer of compost or soil rich in organic matter, and water well.
For the first week or so, the whole bed is likely to heat up and may even start steaming, as decomposition begins. So, I let everything settle for a week or two before planting my summer crops directly in. Alternatively, for an extra soil boost, you could first grow a green manure crop.
The soil level will drop over time as materials settle and rot. Top the bed up with more no-dig layers of brown and green materials (I've been using compost, shredded paper and organic fertiliser).
Climate-resilient benefits of hügelkultur garden beds
Hügelkultur is an excellent way to sequester carbon into your soil while making use of larger gardening waste items and prunings that can be difficult to compost in a small urban garden.
And, over time, hügelkultur gardens can use less water too.
Across my four raised hügelkultur beds, I've set up drip irrigation fed from my rainwater tanks. In this first year, it's crucial I keep these beds moist to get decomposition cranking in the woody materials. But in years to come, I expect these beds to need less regular watering as the logs turn into large sponges, soaking up water and holding moisture for my veggies to draw from.
The logs and organic matter will slowly release nutrients too, which may help to reduce my reliance on store-bought organic fertilisers.
So, by reusing free resources that might otherwise have been thrown away, I've created a thriving annual veggie-growing area that is easy to manage and provides healthy homegrown food for my kitchen table almost every day.
Koren Helbig is a freelance journalist who practices permaculture and grows organic food in the backyard of her small urban Tarntanya/Adelaide home.