It sounds like poor drainage - you could try applying gypsum over the area to see if that helps.

Hi Adricat, yes a little to flat of lawn area, poor drainage, a top dressing of gypsum like Marie K suggests and your turf/ lawn will help out,lawn may have had dynamic lifter applied somewhere along the track and this may also have contained some spore material, or your lawn/soil may have had spores amongst it as well, sometimes even dogs,cats,humans can transport the spores around. A good quality fertiliser in spring will get things going in the right direction, using the wrong fertiliser at the wrong time will make the fungi spread. Good luck. Peter r

do you have any trees around your lawn? all plants live in community with the soil and have an interaction with it called the rhizosphere. Not all fungi is bad fungi. Some varieties break down the rotting material from the grass and then allow the nutrients to be available in the soil. I would go to my local library and get out a lawn care book or general garden pest and disease book to see if there is a picture of your mushrooms in it - if not they are probably either doing nothing except making your lawn a better place!

I also have some toadstools on my lawn, but only in a certain area. The lawn should be considered well-drained because it slopes down away from the house all the way down to the sidewalk. But if the soil is very 'hard' then I can see where that might be considered poorly drained regardless of slope, and where gypsum might help out as a result.

Still, the area where all the toadstools popped up this fall / early winter is: a) Shaded this time of year and b) Right beneath a birch tree whose little seedpod thingies have rained down all over that area where most of the toadstools have popped up.

This is a new lawn (this Spring) from seed and did very well for its first season; quite lush. I'm in Northern Calif (SF Bay area). I fertilized it on a regular/standard schedule. My father in law thinks the toadstools are mainly/likely the result of all the shade that particular section of lawn gets this time of year (with sun low and house getting in the way, relative to other part of same lawn that looks much healthier and has zero toadstools).

Comments/feedback appreciated! I was also wondering if there's any such thing as a 'toadstool/mushroom' killer that I can apply to the lawn. I could care less about chemicals and organics in this politically correct day in age, where my lawn is concerned. Hey, I'm as PC as the next guy (sometimes PIC! ha!) and concerned about environment blah blah blah, but not where my little lawn is concerned; happy to bomb it with chems where warranted.