Plant Doctor Archive

Killing off oxalis

I HAVE just noticed that a patch of oxalis growing in a corner of my garden has developed a mustard coloured fungus on it and is dying off. The fungus is not damaging any other plants growing alongside. Would I be so lucky to have something that could kill off oxalis? And if it is deadly to oxalis, how could I spread it to other oxalis plants in my garden?

I HATE to disappoint you, but many species of oxalis are quite susceptible to rust fungi, which is most likely what you have noticed. Unfortunately, it doesn't kill them. When conditions favour the fungi, oxalis foliage can get so badly damaged it dies off, but the plant will soon sprout away again from its underground corms.

There is no easy way to get rid of oxalis except to remove the corms whenever you work the soil, cover with weed mat to smother them out, or spray them when in full leaf with a herbicide such as Amitrole.

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