Plant Doctor Archive

Unhealthy hostas

I HAVE an area planted in hostas that I mulched with silage. One of the hostas has a problem with the leaves yellowing and the flowers appearing deformed. Should I remove the plant to protect the others?

FROM your photo it looks as if the affected plant has either gone into early dormancy because of some sort of stress, perhaps caused by excessively dry soil (which seems very unlikely), or it's suffering from a disease, probably fungal, causing the foliage to collapse. Disease like this can be brought on by excessive moisture and humidity around the crown of the plant caused by the silage being in contact with the hosta foliage.

Silage can get extremely wet and soggy, so it should be used sparingly as mulch and always kept well away from contact with plants. Scrape away the silage from around the plant and check the crown and any roots close to the surface. If they appear diseased, with areas of brown rot, it's probably best to dispose of the plant.

However, if there are still healthy buds and roots, you might get away with simply removing all the affected leaves and flowers and getting rid of some of the mulch to let fresh air and light into the crown. You won't get new growth until next spring, but the plant may well recover. To help it along, you could drench it with a fungicide such as Phoscheck or No Root Rot to combat any infection that may be present.

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