These are the fruiting bodies produced by fungi that can be found in the lawn. Most are generally harmless and occasionally can be beneficial to the eco system. Although the fruiting bodies are clearly visible it will take an expert to distinguish whether they are edible, so we don't recommend you eat them.
Toadstools in the lawn are not always a cause for concern, however when you get mushrooms in a circle then this could be evidence of a fairy ring, discussed on its own page.
What to do with the odd toadstool or mushroom in your lawn?
Before cutting the lawn, try and remove these using either a rake, or if the lawn is short enough, a stiff brush will help. If you cut the lawn with them on, you increase the risk of spreading the spores and increasing the numbers that may already be there.
We generally find good maintenance of the lawn with Aeration and Scarification reduces the numbers the following year. We also see a high incidence of Toadstools and Mushrooms when we experience extremes of weather, for example when it goes from dry and cold to warm and wet, the humidity will stimulate their activity.
It's also a sign that the microbial activity within the soil is high. This is good as it helps to ensure that when we are feeding the lawns the microbes are helping to share the food around the grass plant.
If you have heard that it is wise to apply a fungicide, please ignore this practice. Fungicides will have an impact on the fruiting bodies that are there for a short time; they will have no impact on the ones beneath the soil which can pop up over night.