Plant Doctor Archive

Water Gardens — Using river boulders

I HAVE been advised against using river boulders in my pond. Why is this?

RIVER boulders and a number of other rocks - certainly cement - leach minerals into the water which can encourage the growth of blanketweed.

However, the problem tends to ease over time and you can counteract it with additives such as Pond Balance.

It is also possible to seal the stones with a clear silicone sealant. This can reduce the problem considerably.

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