We have a 25 acre block of land near Wanaka and we have an abundance of Sorrel (a reddish colored weed with a very long tap root) growing within the grass. It appears to be killing the grass and everything around it. We have been told that it poisons the soil. Help.
Greg Johnston, Wanaka
We can find no information about sorrel poisoning soil. Your description of sorrel is "a reddish coloured weed with a very long tap root" - sorrel has a shallow root with pinkish flowers - itís related species, dock, seems to fit your description better. Both weeds have a tendency to grow in acid soil and poorly conditioned soil which has little organic matter. If you improve the soil conditions, the weeds may disappear. Recommended reading is the book Common Weeds of New Zealand which provides the full picture of a large variety of weeds.