Garden Q&A: On glowing mushrooms and planting trees amid cicada hatch

Jack O'Lantern mushrooms, which grow on decaying wood are poisonous, but also known for a faint bioluminescence.

I though about decorating these big orange mushrooms with little faces for Halloween, but are they poisonous to touch? They came up in the lawn where we took out a tree a few years ago.

Jack O' Lantern mushrooms (Omphalotus illudens) are poisonous, but just wash your hands after handling and don’t eat them, obviously. What makes them most eerie and exciting are their gills that glow blue-green at night, a bioluminescence sometimes called foxfire. Its enzyme luciferase acts upon a compound called luciferin to emit light, much as fireflies do.


Several other wood decay mushrooms do this, too. If you are curious and very determined to see it for yourself, you must sit in a totally dark room for about 15 minutes before you’ll make out the faint but spooky green glow.

Jack O' Lantern mushrooms can be a pathogenic wood decay mushroom on deciduous trees. It’s not a good sign when seen at the base of living oak trees. But it also occurs on old stumps, fallen trees and where old trees were removed, like yours, living on decaying roots underground. That’s harmless. It grows in clusters from July through November.


I want to plant some trees this fall. Will the cicada onslaught of 2021 be a threat to their survival? Do I need to postpone planting for a year?

Periodical cidadas, popularly known as the 17 year locusts, are primarily a problem on new/young trees and shrubs so, yes, 2021 requires some forethought. They emerge in the first half of May and stick around until the end of June. When they slit twigs or terminals to lay eggs, the branch tip dies. This means nothing for a mature tree, but it can potentially kill or stunt young ones when many growing tips are killed.

On the bright side, cicada numbers are heaviest in landscapes of mature trees over 17 years old. If you are in a new home or development where soil was highly disturbed (bulldozed) during that time span, any cicadas in the soil would have been killed. Or, if you live surrounded by fields with few trees, the cicada population will be almost nil.

You can either delay planting until fall next year or plant as soon as the cicadas leave at the end of June. The latter option may require more watering over the summer. Search ‘cicadas’ on the Home and Garden Information Center website.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at Click “Ask Maryland’s Gardening Experts” to send questions and photos.