Myth: Fallen leaves make decent fertilizer for your lawn

Myth: Fallen leaves make decent fertilizer for your lawn

The Myth Of Fall Leaves As Good Fertilizer

fall cleanup, raking, leaves, rake

This is NOT what fertilizer looks like.

Someone says it every year: ‘Why you rakin’ up all those leaves, Bub?  I just leave ’em where they fall and they make a good fertilizer for the lawn!’

This person’s lawn is usually spotty, thin, and just generally awful.

The thing is, decomposing leaves will make the soil more acidic.  If you check back to our article about soil Ph levels (found HERE), then you can see how acidic soil isn’t good for growing grass.

Decomposing leaves also don’t provide nitrogen (N), phosphorous (P) and potassium (K) in the correct amounts to be beneficial for growth.  The things they release can be different depending on how they decomposed, and their amounts aren’t at all consistent.

Good fertilizer has very specific amounts of those elements, and they are designed to help your lawn grow in thick and healthy.

The science that backs this up is pretty solid, and the science says that leaving leaves where they fall is NOT a good way to fertilize the lawn.


We were going to make a fertilizer joke here, but decided to dump it.

Leaving just a few leaves can be alright for the soil.  As leaves break down, the CO2 they release can help to feed nearby plantlife and the test of the broken-down matter can even stick around and help build up the soil.  BUT ONLY IN SMALL AMOUNTS.

Can these leaves help fertilize things?  YES.

Is is just as good as using even the most basic fertilizer?  NOPE.

Do You Like Fungus?  Because This Is How We Get Fungus!

Leaving too many fallen leaves will effectively block any oxygen from getting to the soil and cause it to suffocate.  This can be made even worse when that blanket of leaves is covered by a thick layer of snow for the whole Winter-cycle.  Temperatures will rise in the springtime, water will mix in with that thick layer of leaves, and the dark and damp will give way to fungus and all sorts of nasty stuff that will cause your grass to be spotty and unhealthy.

ALSO: Rotten leaves smell terrible in the spring, and your neighbors will strongly dislike you when their houses are downwind.

Fungus is the big reason lawns tend to come in spotty.  It screws around with the Ph level of the soil (like we mentioned above), and makes it really tricky for grass to grow evenly.  You will see grass growing in clumps with spaces of bare soil in-between.  Not ideal.

Biggest culprit here: soil acidity and fungus. Fixable, but also avoidable.

The best way to get rid of fungus is with direct sunlight.  Cleaning up those leaves will remove any shade they were providing, and will expose any potential fungi with good, clean sunlight.

I mean, look at the little weirdo.

Happy Fungus loves it when you don’t clean up your leaves. like… the unsettling kind of happy.

Maybe you like fungus.  Maybe that’s your thing (we aren’t judging, it’s cool).  If it IS your thing, then you will want as little sunlight as possible on the areas where you want fungus to grow.  You will also wants there to be a ready supply of constant moisture and maybe a little bit of something dead to kick-start the process.  Leaves work pretty well, we’ve heard.

The Short Version

  1. Leaving your leaves where they fall is not a good way to fertilize your lawn.  It IS however, a great way to encourage fungal growth and an even better way to make your soil more acidic. They also make your property stink in the Spring.
  2. Cleaning up your leaves before the winter is a great way to promote a healthy lawn, it keeps your soil balanced and ready for new spring growth.

Of course, please feel free to form your own opinions on this.  Some folks will offer up the argument that grass and trees have grown alongside eachother since the dawn of time, and have managed to do so without human intervention (raking).

The problem with that argument is that lawns (as we know them) tend not to occur naturally. They grow in because we nurture them and provide the optimal conditions for them to thrive. Ask yourself this: Why don’t you ever see nice green lawns growing in the middle of the forest? And big open fields of grass often exist because there aren’t too many (leaf-dropping) trees in them.

Happy Gardening!

~The Greencare Team