Plant Doctor Archive

Lichen-covered tree

MY beautiful old apple tree is covered in lichen. I like the look of it, but I'm worried it's damaging the tree. Should I do something about it?

LICHEN doesn't do the tree any harm. It's actually a good sign, as lichen needs clean air to survive. In parts of the world where pollution is bad, lichens are becoming rare.

Lichens are two organisms living in symbiosis - a fungus shelters an alga which provides food for the fungus. Vigorously growing trees shed bark regularly, which tends to limit lichen growth, so it's also a sign your apple tree isn't growing very strongly. I suggest you feed the tree to encourage more growth and, if you do wish to remove some of the lichen, simply try brushing it off. If you want to deal to it on a larger scale, spray with lime sulphur in winter when the tree is dormant, or paint the spray solution on to the lichen.

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