Black film on Linden tree and plants

Asked August 20, 2017, 8:21 PM EDT

I have what looks like black soot all over the hostas and vinca vine that sit under my Linden tree. The Linden tree also has this black substance all over the leaves. The leaves seem to have damage to them as well. I've never seen this before in previous years. I can wash the film off if I scrub hard enough but it does not come off with a spray of water. Does anyone know what this is??? And how I can get rid of it for the future?

Hennepin County Minnesota hostas linden tree horticulture

1 Response

I think it is sooty mold. Aphids feeding on your linden drop an excrement called honeydew. You might have noticed that the plants under your linden were covered with a sticky substance about a month ago. The honeydew is an ideal growing medium for sooty mold. Sooty mold can weaken the plant by reducing the photosynthetic layer. To prevent sooty mold in the future, you should watch for and deal with the aphids in the linden. Read here:
https://www.extension.umn.edu/garden/insects/find/aphids-on-deciduous-trees-and-shrubs/
http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advi...