- While the toadstool or fruiting body is the most visible sign of the fungus, these are transient structures designed solely for the dispersal of spores
- Many of the fungi produce their fruiting bodies in autumn, although again this will vary with the species. For the rest of the year the presence of the fungus is not as obvious, existing as numerous fine threads or filaments known as hyphae. Together, these make up what is known as the mycelium of the fungus
- Occasionally, when environmental conditions are suitable, prolific growth of mycelium occurs and becomes visible as a white, fungal-smelling growth within the soil or in a compost heap or bag
- The vast majority of fungi producing toadstools cause no harm to garden plants and should not be a cause for concern
- There are, however, a few exceptions and one of these, honey fungus (Armillaria spp.), is the most damaging disease of garden trees and shrubs
- Some of the fungi causing fairy rings in lawns (e.g. Marasmius oreades) also produce toadstools
The vast majority of fungal species producing toadstools in gardens are likely to be of two types:
Saprophytes: This group of organisms feeds on dead plant and animal remains and they are usually beneficial to plant growth, as they release minerals and nutrients back into the soil and help form its organic humus content. One saprophytic species found in gardens that may cause offense is the stinkhorn (Phallus impudicus). The fruiting bodies have a thick white stalk and dark head, and the extremely strong odour of decay they produce is often the first indication of their presence.
Mycorrhizae: a term that translates as ‘fungus root’. These fungi form an intimate association with the roots of plants, including many trees and shrubs.This is a beneficial association known as a symbiosis; the fungus derives nutrients from the plant, but the fungal hyphae also grow out from the roots into the soil, enabling the plant to obtain water and nutrients from a much greater area than it could with just its own roots. A well-known example of a mycorrhizal fungus is the poisonous fly agaric (Amanita muscaria) with its bright red cap, spotted with white scales. This is associated with birch and some conifers.