Mulching leaves into your lawn

Leaves bring benefits to your home lawn

By: Sandy Feather ©2009
Penn State Extension

Q. A friend of mine says that it is okay to run fallen tree leaves over with a mower to chop them up and just leave them on the lawn for the winter. Is that really a good idea? Wouldn’t that increase the amount of thatch in my lawn?

A. It depends on how many leaves have fallen on your lawn. It would not hurt to shred the leaves with your lawn mower so that the pieces of leaves left on your lawn are small enough to break down quickly and not smother the grass. If you see more leaves than grass when you are finished, it is too much; if you can see more grass than leaves, it should not be a problem.

Do mulching mowers work?

A mulching lawn mower that sucks grass clippings and leaves back into the blade for additional chopping would probably do a better job than a conventional mower.

Benefits of Leaves for Lawns

Shredding the leaves and allowing them to remain on the lawn adds some nutrients and, more importantly, organic matter to the soil. Organic matter improves the soil’s capacity to hold water and nutrients as well as creating a better environment for strong root growth. Using fallen leaves on your lawn and landscape beds also keeps organic matter out of the landfill.


Too many leaves?

If you have too many leaves for this to work well, you have the option of bagging some of the leaves as you mow. Dump them into a compost pile, or use them as mulch in shrub or flower borders, or under trees in your yard. (It is not a good idea to do this with whole leaves because they break down very slowly. They can mat together and become almost water repellent). Composted, shredded leaves break break down over the winter to produce leaf mold, a valuable and attractive mulch for flower beds. Turning the compost pile when the weather allows speeds up this process. Once you get the worst of the leaves cleaned up, you can mulch the remainder with the mower and allow them to stay on your lawn.

fall lawn leaves
With heavy leaf accumulations it will be necessary to rake some of the leaves up first before using a mulching mower on the rest

Thatch is nothing more than a tangled mat of sloughed off stems and roots that forms as a grass plant grows. Grass variety, soil pH (acidity or alkalinity), and your watering and fertility practices have much more impact on thatch formation than leaving a thin layer of finely shredded leaves behind in the fall.


Grasses such as Kentucky bluegrass and creeping fescue that spread by rhizomes (underground stems) tend to create more thatch than bunch-type grasses such as perennial ryegrass and turf-type tall fescue. Soil pH that is too low or too high inhibits the activity of soil microbes that help break thatch down. Maintaining soil pH between 6.5 and 7.0 keeps them working as long as soil temperatures remain above 40 degrees.

Watering Methods

It is always best to water an established lawn deeply and infrequently. If you apply an inch to an inch-and-a-half of water once a week, it penetrates deeper into the soil profile, which encourages the grass to have deeper roots. If you water shallowly and frequently, it encourages a shallow root system that is vulnerable to hot, dry weather. These roots often die and add to the thatch layer.

Fertilizer Application

Fertilizing your lawn too frequently creates excessive growth and contributes to thatch buildup, too. A standard recommendation is to fertilize home lawns three times a year: mid-late May, late August-early September and mid-November, applying one pound of nitrogen per thousand square feet each time. This last application should be made after grass has ceased actively growing, but before the ground freezes. It may seem counterintuitive, but many plants, including grasses, put on tremendous root growth in late fall.

To calculate how much of a given fertilizer is needed to apply one pound of actual nitrogen, simply divide one pound by the percentage of nitrogen in fertilizer you are using. That information can be found by looking at the three numbers – known as the analysis – found on every package of fertilizer. They indicate the percentage of nitrogen, phosphorus, and potassium and are always listed in that order. For example, to apply one pound of actual nitrogen per thousand square feet if the fertilizer you are using has an analysis of 28-3-10, divide 1 by .28. The result is 3.6 pounds of 28-3-10 per thousand square feet.


Transplanting in Late Fall

Fertilizer burn on lawns

Freeze Damage to Outdoor Plants


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