Fighting off tree roots

Posted on April 26, 2011

When establishing our raised garden beds, I had thought this would proof us against issues in the soil, including the impact of neighbouring trees. How wrong we were. The camphor laurel has proven to be very vigorous, and when I turned over the soil in the bottom two beds, I found feeder roots coming up through the bottom of the bed. No wonder the plants weren’t growing properly!

No choice but to take drastic action (short of cutting down the noxious tree itself).

The starting point was to fully dig out the garden bed, which was no small task, as there’s 1.5 tonnes of soil by a previous calculation.

Having dug the bed down the level of the original gravel, I laid down a layer of bark mulch. This is something that I saw on Gardening Australia, where the nitrogen draw-down of the mulch rotting creates a low nitrogen layer. This should help to discourage or deflect the tree roots. (This is the experimental bit, I hope it works!)

Multiple overlapping sheets of weed mat should then form an impervious barrier to the roots, at least to some degree.

With the gardening in mind, I’d scavenged some old carpet from the side of the road. This was laid in to protect the weed mat against garden tools, and to provide an additional layer of proofing against roots. (And yes, I’m aware of the debate about whether carpet should be used or not for these purposes; in the end I decided that more was better than less when it came to roots.)

Getting 1.5 tonnes of soil back into the bed was my final workout. Having read that roots breaking down release toxins, I carefully removed the camphor laurel roots when refilling the bed, which slowed the whole process down.

Hopefully that’s all fixed now, and I can get back to growing vegetables!