365 Urban Species. #179: Amethyst Deceiver

Photos by cottonmanifesto. Location: Hillside of onramp between Jamaicaway and Olmsted Park, Boston.

Urban species #179: Amethyst deceiver

Most familiar urban fungi (and likewise, most fungus species represented in this project) are wood-digesting fungi. They live as filaments in dead wood, feeding on their surroundings, and fruiting as mushrooms or brackets when it is time to reproduce. But there is another major lifestyle adopted by members of kingdom fungi, that is much more rarely seen in the city. We all must learn the word "mycorrhizal," (Mike-o-Rise-ul) which describes how certain fungus species live. A great many fungi live in mycorrhizal association with plants. They live amongst the roots of plants, feeding on the carbohydrates the plants make from sunlight, while helping the roots obtain more water and nutrients.

Many colorful and interesting mushrooms grow from mycorrhizal fungi that associate with tree roots. This symbiosis takes time to develop, and the short life span of urban trees (5 to 10 years for a tree planted in the city) means that the tree may die before it and the fungus can find each other. Also, urban soil is a substance constantly on the move, being dug out of one place and trucked into another, which poses another obstacle to mycorrhizae. Only in those places in the city where the soil is stable and healthy, and the trees have lived a long time, do we find mycorrhizal mushrooms.

This group of amethyst deceivers was growing along the edge of a traffic onramp, between the Jamaicaway and the beginning of Olmsted park. A few moderately old red oaks loom nearby. If you didn't know that the amethyst deceiver was mycorrhizal, you wouldn't think they had anything to do with the oak trees. But if not for the oaks, these exquisite little gems wouldn't be there at all.

The amethyst deceiver is a member of the genus Laccaria, which includes L. laccata, a highly variable mushroom easily confused with a number of other species. Thus, L. laccata is known as the deceiver. L. amethystea was once thought to be a variety of L. laccata, but has been granted full species designation. That complicated but pedestrian story is how this pretty little mushroom acquired a name that makes it sound like a gothic rock band.