GREEN THOUGHTS: Loving, and leaving, your leaves

“The falling leaves drift by the window

The autumn leaves of red and gold

I see your lips, the summer kisses

The sun-burned hands I used to hold”

JOHNNY MERCER’S LYRICS are a little too personal in Covid time, and the hands may be sun-burned for a most unromantic reason—too much yard work. And if you follow the standard practices of raking and bagging, the autumn leaves only add to the toil.

Those same leaves which inspired the poets have gained the attention of a much more practical lot, scientists at state universities. Researchers at Purdue point out that chopping up leaves with a mulching mower and leaving them on the lawn is less time consuming than blowing, raking or vacuuming them away. Mulching leaves has no effect on soil pH or nutrient availability. It does not increase the amount of thatch or the chances the lawn might come down with a fungal disease.

In fact, mulching leaves into a lawn often improves the soil structure, which, in practical terms, means the soil particles stick together better. This, ergo, means the soil will be less compacted, contain bigger pore spaces better able to hold both air and water, and increase the activity of beneficial soil-dwelling organisms. So, on a microscopic level, mulching is a win-win proposition for both you and the ground you stand upon.

Okay, you say, mulching works in a research trial, but what about the real world? Obviously, heavy doses of leaves, even if chopped, can smother and kill a lawn, so this new advice has you mowing more often. Mulching dry leaves is much easier on your machine than wet leaves, so you’ll have to watch the weather, too. And it might be tough to follow this practice on a small lawn surrounded by many trees, where there just isn’t enough space to macerate a tremendous volume of dead foliage into the turf. In that case, I still see a need for raking, but there is a silver lining: leaves make excellent fodder for a compost pile, the best solution of all.

What about the additional pollution made by running your mower more? The alternatives aren’t attractive. Piles of leaves raked to the curb leach phosphorous into storm sewers, certainly an environmental negative. If those leaves are eventually burned or dumped in landfills the story only gets worse. And even if they go to a large-scale composting facility, my hunch is that more fossil fuel is used in their collection and trucking, then processing into compost, than would be if you kept the leaves home and mulched them yourself.

Michigan State scientists have discovered another positive to letting leaves lie: weed reduction. Researchers there made applications of pesticide-free, pulverized leaves from red, sugar and silver maple and red oak trees to lawn grass and dandelion plots in the fall, then counted the number of dandelions in each plot the following spring. Amazingly, those familiar yellow-flowered weeds were reduced by up to 80% after just one application. Another reason to leave your rake on the rack.

David Chinery is the horticulture educator for Cornell Cooperative Extension of Rensselaer County. Reach him at

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