Plant Doctor Archive

Bamboozled

I HAVE a problem with bamboo spreading in an established garden that I have recently inherited. So I have three questions. Can bamboo clumps be contained? How can I completely eradicate it from some areas? And is it possible to kill the bamboo without harming nearby established camellias and native bush?

THERE are basically two types of bamboo - running and clumping. The running varieties cause the most problems as they spread over quite large areas once established, even under concrete paths and fences. Clumping types also spread but are much more restrained, rather like a clump of native flax, and they're the best types to choose for a garden. To contain running types try the following:

• If practical, mow closely around the clump. This way you'll cut off new shoots as they emerge from the ground and restrict spread.
• Dig a trench all round the clump at least 50-60cm deep and 30cm wide. In clay soil you may get away with a shallower trench. Rhizomes are generally in the upper layer of soil so they should grow out into the trench where you can simply cut them off. Keep the trench open all year round, especially in autumn when rhizome growth is at its peak. Or line the wall of the trench with a barrier, such as concrete or galvanised steel, and replace the soil - but watch out for rhizomes sneaking over the top or breaking through.

To eradicate bamboo you have two options:

• Dig out the entire clump. This can be an almost impossible task to attempt by hand. You may need a digger for a large clump. Make sure you get all the rhizomes out or they could regrow.
• The easier option is to use the herbicide Amitrole or Activated Amitrole. The best approach is to cut all the bamboo stems down to the ground, wait until there's lots of fresh new growth coming through then spray when it's around a metre high, ideally in spring or autumn when growth is vigorous. It will take several weeks to have an effect and you may have to spray again periodically for the next two or three years to kill it off completely. Both products are safe to use around your established camellias and natives as long as you don't get any spray on their foliage.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.