Should I worry about these fungi?
Q Can you please identify these fungi? They are growing between original railway sleepers used for a raised bed with a thriving acer growing in it. Are they something I need to remove? Patricia Lush (via email)
A Without an exact identification it is difficult to be certain whether this is something to worry about or not. However, I can reassure you that this is not honey fungus, which is the one to be most worried about.
It is almost certainly a saprophytic fungus growing on dead material rather than living material.
If it is feeding on the sleepers then it could eventually become a worry, as it will be causing the decomposition of the wood, which will rot away. But given the sleepers have been steeped in creosote I think this is unlikely to be the case and it is more likely the fungus is growing on organic material in whatever soil/ compost you have in the raised bed.
For example, this could be bark or wood waste, green waste (found in some multipurpose composts), animal manure or even home-made compost – anything that was once living material.
Fungi that feed on dead material rarely cause harm to living material and should not be a problem for anything growing in the raised bed. However, as long as the fungus has a food source it will probably continue to appear every year until it has exhausted it.
You could remove the mushrooms to prevent the fungus setting spores and therefore hopefully prevent it spreading. It is best to gently tease them out of their space.
However, the main bulk of the fungus is actually the part growing in and on the food source – it is much harder to remove this as it practically impossible to see! I would be inclined not to be too concerned as long as the fungus is not growing on the wood, and just to remove the fruiting bodies as they appear.
Most fungi thrive in damp and humid conditions. It might be worth maximising ventilation around your raised beds to decrease humidity levels if possible, and you could also dig through the compost to improve aeration.