Extension News

Ask the ISU Extension Garden Experts: Mushrooms and Frost Damage


One of my houseplants has several small, yellow mushrooms on the surface of the potting soil. Will the mushrooms harm the plant?

The small, yellow mushroom is probably Leucocoprinus birnbaumii. The fungus is sometimes referred to as yellow houseplant mushroom, yellow parasol or flower pot parasol. This species can be found outside in summer, but is most commonly found year-round with potted plants or in greenhouses. The small, lemon yellow mushrooms are about one to three inches tall with one to two-inch oval or bell-shaped caps. They may appear singly or in clusters.

The Leucocoprinus birnbaumii fungus breaks down dead organic matter in the potting soil. It does not harm living plants. However, the mushrooms are regarded as poisonous to people and animals. If pets or small children reside in the home, it would be wise to remove the mushrooms as they appear. Fungicide treatments are generally not effective against mushrooms.

Which perennials are most likely to be heaved up out of the ground in winter?

Repeated freezing and thawing of the soil during the winter months can lift up or heave some perennials out of the soil. Heaving exposes the plant’s crown and roots to cold, dry air. Perennials that have been heaved up out of the ground may be seriously damaged or destroyed.

Perennials most susceptible to heaving are shallow-rooted plants and those planted in late summer or early fall. Perennials prone to heaving include garden mum (Chrysanthemum spp.), Shasta daisy (Leucanthemum spp.), painted daisy (Tanacetum spp.) and coral bells (Heuchera spp.). Perennials planted in late summer/early fall are susceptible to heaving because they don’t possess extensive root systems and are more easily pushed up out of the soil. Generally, most well established perennials (those in the ground for one or more years) are not prone to heaving.

Heaving of perennials can often be avoided by planting in spring and mulching. Spring planting is especially important for garden mums, Shasta daisies and other perennials prone to heaving. Perennials planted in late summer/early fall should be mulched with several inches of straw or pine needles in late fall.


Contacts :

Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu

Del Marks, Extension Communications and External Relations, (515) 294-9807, delmarks@iastate.edu