Lawn Care Part IX – Leave the Leaves? Yes and No, How and Why

It’s fall, and hopefully your lawn is looking great after following along with us all year.  The lawn care season is coming to a close and we are getting to the last tasks before wintertime.  One question I hear often is: I’ve heard I can leave my fall leaves but how do I do it without smothering my grass?

As a watershed organization employee, I will be faulted if I don’t mention that you shouldn’t pile your leaves onto river banks or streams.  When we paddle down the river, we often see discarded lawn debris on the riverbank. Even though leaves and grass clippings are natural they can add extra nutrients into the water contributing to dangerous algae blooms that can kill aquatic life. If you live in a suburban area, please don’t rake your leaves into the street, but bag them so that the leaves can easily be removed before clogging storm drains and either cause local flooding or be deposited in your local waterway again contributing excess nutrients. 

Chopped up fall leaves

How can I leave my leaves without smothering my grass?
Yes, you can leave your leaves, but there is work involved and now is a good time to get started.  If your lawnmower has a mulching blade, you can use that but otherwise, the basics of leaving your leaves is to keep mowing over them until they get chopped up really well and filter down to the soil surface. The best time to do this is when the leaves are dry and have your mower blade set at 3 inches or higher.  Make sure that the grass is still visible and that there isn’t a wet blanket of chopped up leaves on the surface of the grass. 

Your fall leaves can be used in other ways in the home landscape:

As an insulator for your landscape plants: Depending on your property and the number of trees you have, you can use your leaves for other areas of your landscape.  Pushing some of your leaves to the base of shrubs and other landscape plants will give them a cozy blanket protecting them from frosts and temperature swings in the winter. 

As wildlife habitat: Leave them in the woods if that’s where they fell. Depending on the setting of your lawn, the leaves can be left in wooded areas to the benefit of the wildlife nearby.  Turtles, amphibians, and insects use leaves for shelter and as a food source – removing them from your property will disrupt the local life cycle. 

As organic compost: Leaves can also be a great compost and mulch source for your landscape bed and compost piles.  To put them in your beds, you would need to shred them down. This article from Rutgers Masters Gardeners details the ways to handle your fall leaves for mulching and composting among other great tips.  

When should I remove my leaves?
There are also some leaves that you will not want to leave behind.  If you have a black walnut tree in your yard, the leaves have the same chemical found in the roots of the trees (juglone) that can inhibit plant growth.  If you have maple tar spots on your leaves – and find then unsightly – you can try to remove them from your property, but the fungus tends to overwinter on any remaining leaves and can reinfect them come next spring.  The fungus doesn’t harm the tree but a heavy infestation can cause early leaf drop and occurs not only on maple trees but also box elder and sycamore trees.