Sandy Feather

Dog stinkhorns (Mutinus caninus), a type of fungus that grows in the garden.

Q. I had these really strange looking — and bad smelling — growths in a couple of my landscape beds last September. Can you tell me what they are and if they are harmful to people or plants? Can I spray something to get rid of them?

A. The writer included some photos of what looked like dog stinkhorns (Mutinus caninus). They are relatively common in mulched areas and even lawns when environmental conditions favor their development. Warm, humid weather, frequent rain and moist soil favor the growth of many fungi common in areas rich in organic matter.

Stinkhorns typically appear from late summer into the fall, appearing as yellow-orange to bright orange finger-like stalks that grow from egg-like structures half buried in the soil or mulch. The stalks are topped with caps of brownish-green slime that contain spores. The cap develops a putrid smell that attracts flies to land and carry spores off to germinate elsewhere.

Most sources listed them as inedible, but none listed them as toxic. The smell alone should discourage sampling, but you can dig them out and compost them or send them out with the trash if you are concerned about children eating them.

Stinkhorns are saprophytes, a large group of fungi that break down organic matter to absorb nutrients from it. They do not cause disease in live plants, so your landscape plants are in no danger from them. Other familiar saprophytes are bird’s nest fungi and slime molds (often called dog vomit fungus), commonly found in landscape beds mulched with shredded wood or wood chips.

There is nothing homeowners can apply to stop them from growing. I noticed some websites recommended spraying fungicides, but there is no research-based information to support doing so. The best recommendation is to ignore them. They shrivel up and disappear almost as suddenly as they appear. If they are too numerous or otherwise disturbing, you can remove and dispose of them.

These fungi are part of the natural decomposition process that includes the activity of fungi, bacteria, insects and other arthropods, birds and mammals. Stinkhorns grow in wild areas as well as more urban places — all they need is the right weather conditions and a substrate of organic matter. Of course, the transformation of organic matter into humus that in turn improves soil structure and enhances growing conditions for plants is one of the reasons we use organic mulches in the first place. Few people notice the activity of these fungi in natural areas where they turn fallen trees into nurse logs that nurture germinating wildflower seeds and young saplings. They are just doing their job.

First published on January 28, 2012 at 12:00 am