[Grubbypaws]

How important is it to clear the lawn of fallen leaves? It is a job that I have always done but I dont know why 

If I just leave the leaves will it do any harm to the grass? I am trying not to be too tidy this year having read about overwintering insects and larvae etc plus it always worries me that trampling over the wet lawn raking up leaves compacts the ground at this time of year.

What does everyone else do and why?

[Yorkie]

It won't do the grass any good really by leaving the leaves on it.  They prevent air and light getting to the roots, so the grass cannot produce chlorophyll and is weakened or even killed off.  If only weakened, there is risk of fungal or other diseases taking hold.

The leaves will also rot down, contributing to what is known as thatch which will impair the grass' health as it blocks air to the roots again (it's why you scarify - to remove moss and thatch).

You won't do much harm to the wet lawn unless it is absolutely really sodden - you should keep off frosted / frozen lawns though.

[Jamie Butterworth]

Cant add much else to what Yorkie has put

Like she says, it can kill of the grass, this is purely because grass, and all plants produce there own food through photosynthesis, they produce this through light, and if the leaves cover the grass and stop lighting getting to it, they cant produce food and will die.

Walking on the grass while its wet wont do any real damage, it can make it slightly boggy but it will soon recover. But don't walk on it in frost, or even the days after a frost, even if the grass has thawed out. This is because the soil below will still be frozen, and some of the grass roots will still be frozen, so by walking on the thawed out grass, you can cause the soil to move, and sheer off the roots where they are still frozen. Ive knocked up a quick picture to help explain this

[Jamie Butterworth]

Plus, if you just leave them on your grass, then you dont get to get leaf mould from them

[Junie]

If you have horse chestnuts with those leaf burrowing insects, it is thought that they over winter in the leaves on the ground, so they really need to be got up!  My job soon as I have 2!!

[Yorkie]

If you have horse chestnuts with those leaf burrowing insects, it is thought that they over winter in the leaves on the ground, so they really need to be got up!  My job soon as I have 2!!

I have those leaves and those leaf miners.  Do not try to make leaf mould with them; put them in the green waste.

[Grubbypaws]

Well now I know, thank you all. I didnt know about the sheering effect after frost either, thanks for the diagram Jamie.

[sunshineband]

So get out thant rake and rake up all your leaves off the grass -- it'll look shocking aftrwards but soon recover

OR
 get them all up and ready chopped too, by using your lawn mower 

[Grubbypaws]

Sunshineband,  mowing the leaves sounds the way to go; is it still OK to cut the grass this late in the season?

[sunshineband]

Sunshineband,  mowing the leaves sounds the way to go; is it still OK to cut the grass this late in the season?

It certainly is