Author: Dianne DeLongchamps
Should I rake, mulch or bag my fallen leaves this fall?
Mulch your leaves into the lawn with a mower when the layer is light to moderate. CSU Extension’s test is that if you can still see grass through the chopped leaves, the layer wasn’t too thick to mulch. Leaves thick enough to hide the grass need to come off by raking or bagging.
Clean Air Lawn Care treats lawns in Fort Collins, Windsor, and Timnath, and the same leaf guidance applies to yards in all three towns.
Why mulching is worth doing, not just a shortcut
CSU Extension’s Using Leaves in the Landscape guidance treats mulching as real soil-building, not a shortcut. Running a mower over a light-to-moderate leaf layer, ideally with a couple of passes so the pieces get small, adds organic matter back into the soil, which slowly turns into nutrients and cuts down on how much fertilizer a lawn needs. The same guidance notes that mulched leaves don’t build up thatch, which is a common worry, and cites Purdue University research finding that even high mulching rates didn’t hurt turf quality, color, or soil pH.
How to mulch leaves with your mower
CSU’s guidance on using leaves in the landscape gives three steps for mulching leaves into the lawn. Set the mower deck to its highest setting, take off the bagging attachment, and make at least two passes over the lawn so the leaves are chopped into small pieces. A second CSU Extension page, How to Mow, Compost, and Mulch Leaves, says the goal is leaf pieces small enough to filter down into the turf.
What CSU says about raking
How to Mow, Compost, and Mulch Leaves leans against raking leaves away at all. Its advice is, “So this year, don’t rake those leaves away, embrace them!” The same page says to chop leaves into small pieces that can filter into the turf, and CSU’s Using Leaves in the Landscape guidance adds that mulching leaves into the lawn does not lead to thatch accumulation, so choosing mulch over raking carries no thatch penalty. Raking and bagging is the fallback for a layer too thick to chop, not the default for every yard in Fort Collins, Windsor, or Timnath.
When mulching stops being enough
A thick, matted layer of leaves, generally the point where mowing doesn’t reveal grass underneath anymore, blocks sunlight and airflow to the turf. CSU’s page on how to mow, compost, and mulch leaves says to avoid leaving leaf litter on your lawn so it doesn’t smother your grass, and to prevent mold and disease growth. At that point, raking, bagging or blowing the leaves off is the better call.
The practical approach: mow first, then decide
The right answer depends on how many leaves are actually down, not one blanket rule. On most properties, a mulching pass is worth trying first. If the mower chops the leaves small enough that you can see grass through them afterward, you’re done. That layer breaks down on its own over the following weeks. If leaves are still piled thick after mowing, that’s your cue to switch to raking or a blower for a full removal pass instead of mulching again and hoping. Whichever way you go, the goal is the same: do not leave a layer of leaves thick enough to hide the grass sitting on the lawn.
Where removed leaves should actually go
Instead of bagging leaves for the curb, composting them or using them as mulch around garden beds and plants keeps the same soil benefit without smothering the lawn. That keeps the material working for your yard instead of heading to a landfill.
CSU gives specific direction for both uses. Tree leaves are high in carbon, which CSU considers a “brown” material, so they go into a compost bin in combination with materials high in nitrogen. CSU’s mow, compost, and mulch page says whole leaves are preferable to shredded ones for composting. In garden beds, leaves are a source of organic matter, and they can be used as mulch to insulate tender or newly planted plants. The same page suggests a layer of three to six inches of shredded leaves as insulating mulch around tender or new plants, and a six- to eight-inch layer of leaves in vegetable gardens.
Not every tree’s leaves mulch the same way
Most common Front Range shade trees break down fine in one or two mowing passes. Bigger or waxier leaves, oak leaves especially, sometimes need an extra pass or two before they’re small enough to avoid matting. CSU’s mow, compost, and mulch page also says oak leaves decompose slowly, so chop them well and use them in small quantities when you compost them. If you’re not sure whether your trees are cooperating, mow a pass and check: can you see grass? That tells you everything you need to know.
October in Northern Colorado can hand you a 70-degree afternoon and a hard freeze that same night, sometimes in the same week. Luke tracks the forecast for every property we treat, because that’s the only way to get this timing right instead of guessing. If you want a second opinion on where your own yard stands, we’re glad to take a look.
Clean Air Lawn Care Northern Colorado is owned by Dianne, Paul, and Luke DeLongchamps — a family business serving Fort Collins, Windsor, and Timnath with organic lawn treatments and solar-powered electric equipment.
