Leucocoprinus birnbaumii

Yellow parasol mushroom is easily recognizable by its small size, and bright lemon yellow oval or bell-shaped cap that fades to a white color with age.  They reach a height of 1 to 3 inches tall.  While they can grow outdoors in clusters, or singularly, they most commonly occur in potted plants, greenhouses, and compost piles where they thrive in warm, moist conditions.  In outdoor conditions, they are most often seen in the summer while in indoor conditions they appear year-round. They work to break down organic matter found in soils and they do not harm living plants. However, remove mushrooms as soon as they appear if pets or small children have access to the area.  Overwatering of potted plants can cause them to appear and they are difficult to manage once established. Fungicide applications are generally ineffective against mushrooms. 

Quick ID:

• CAP: Small, 1-2 inches in diameter, bell-shaped, fragile, margin striate, bright yellow, and covered with powder
• GILLS: Free from stalk, yellowish white
• STALK: Slender, slightly enlarged at the base, covered with bright yellow powder
• ANNULUS (ring): Bright yellow, covered with yellow powder, moveable up and down the stalk, often breaking loose
• SPORE PRINT: White, spores ellipsoidal, smooth