Plant Doctor Archive

Lichen on my azaleas

I INHERITED several azaleas in our recently purchased property, but they have a lot of lichen growing on them. They only have leaves towards the top of the stem and I wonder if the lichen is restricting their activity. Can you recommend a remedy?

ALTHOUGH it may look unsightly, lichen is a good sign - it's an indication of good air quality.

Lichen is actually two organisms: a fungus and an alga, living in symbiosis. The fungus shelters the alga and receives food in return.

Lichens are generally harmless to plants, but if you want to remove them there are several things you can do. You could prune your leggy azaleas back quite hard after they've finished flowering in spring. This would probably remove most of the lichen-affected wood. They'd look bare for a few weeks but will soon put on fresh new growth, especially if you give them a light dressing of a fertiliser for acid-loving plants. Or you could simply rub the lichen off by hand. Wear a pair of gardening gloves to save your skin.

Alternatively, try spraying with lime sulphur, available from garden centres. Be careful, as lime sulphur can damage the foliage of many plants. Try it on a small area first and wait a couple of weeks to see the result. The best time to spray is when the plants are dormant, in winter. Or paint the spray solution directly on to the lichen with a brush to avoid getting it on the leaves.

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