Plant Doctor Archive

Lime chips detrimental?

I RECENTLY redesigned my whole garden and put lime chip down over weedmat. I kept some of the existing plants - two roses, a lilac and a small kowhai tree. I realised, too late, that lime chip is detrimental to the plants and have now pushed the stones away from them to ensure no more lime leaches into the soil. Will this action be enough to save the plants? I used the lime chip around the top of terracotta pots and grasses as well, to their detriment.

I CHECKED with the technical representative at Dalton's, who produce much of the lime chip available in garden centres, and he confirmed my own opinion. Lime chip is made from hard rock which does not break down or dissolve readily and generally has no effect on the soil. It's quite a different material from the garden lime you buy to raise soil pH.

However, when you first buy lime chips there can often be quite a lot of fine lime dust covering them, and this could possibly have a slight effect on soil pH, but should not cause serious problems.

The best thing to do is to rinse the chips before using them around plants to remove any dust. I don't think it likely your roses, lilac or kowhai will suffer any ill-effects.

I'd be surprised if lime chips would have had a seriously detrimental effect on your grasses in the terracotta pots. Grasses do generally prefer slightly acidic soil, but they also have a great tendency to dry out in containers, and terracotta pots can dry out very quickly.

While a mulch of pebbles or chips can be useful in helping to keep in moisture, it can also give you a false sense of security as you can't actually see how dry the mix is becoming. I've fallen into this trap myself. It could be your grasses suffered from lack of water rather than from the lime chip

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