For any one who doesn't know it's a Tree Recycler, Soil Generator and Improver, Productive and Pollination Plant Mound, Compost and Carbon Sink all in one. After one year they become self-irrigating - assuming all goes well. It's important the logs are chosen correctly so as not to be repellent to other plants - so walnut, casuarina (she-oak), eucalyptus and other allalopathic species are not wood sources to use.
These seem to be more popular overseas than in Australia though I aim to change that!
Picture courtesy of www.permaculture.co.uk - I trust they are happy for me to use the picture as it is in the interests of a common cause - and Hugel Kulturs don't seem to be de rigeur at all in Australia. This pic gives you a good insight in to how they are constructed.
Ideally a swale will be built in too to redirect any water run-off and act as a biofiltration media for the garden.
