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How to Mulch Leaves (And Why You Should)

How to Mulch Leaves (And Why You Should)
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So you’ve been dreading the routine fall chore of raking leaves off your lawn, and someone has suggested that you mulch them. But how exactly is it that you mulch leaves?

Leaf mulch is broken-down leaf litter that you can spread over your lawn or flower beds. You can mulch leaves into shreds by running over them with a lawnmower. Other ways of breaking them down involve using a hand mulcher, stand-alone mulcher, or string trimmer.

There are many benefits to you as the homeowner, your lawn, and local wildlife of mulching leaves instead of raking them for collection. So let’s examine these benefits and how you can go about mulching leaves in your yard.

Why You Should Mulch Rather Than Rake

Leaves tend to mat, creating a barrier that air and water can’t get through. This barrier will choke your turf; however, shredding the leaves will break up the barrier and allow air, water, and light to get through.

This process of shredding the leaves is known as mulching. You can mulch as much as 6 inches of leaves into your lawn, provided you shred them fine enough.

Leaves are an outstanding source of nutrients and minerals, with 50 to 80 percent of the nutrients and minerals in a tree ending up in its leaves and then being dropped to the ground. By mulching, you return these nutrients and minerals to the ground rather than giving them away.

As microorganisms and earthworms break leaves down, they return nutrients to the soil without affecting turf quality or performance. Some leaves, such as those of honey locust, are high in nitrogen, which boosts plant growth.

There are numerous other benefits to mulching, namely:

  • Leaves such as sugar maple leaves reduce the germination of broadleaf weeds such as dandelions. Doing so reduces your need to weed or to apply herbicides.
  • Mowing the leaves together with the grass mixes the carbon-rich leaf shreds with the nitrogen-rich grass clippings, resulting in both breaking down more quickly than they do on their own.
  • Mulching leaves reduces the volume of leaves to about one-tenth, which helps significantly with their disposal.
  • Mulching saves you time and effort, as it incorporates into your regular mowing schedule rather than being another time-consuming and labor-filled chore.
  • Leaf mulch improves soil’s moisture retentive ability, which reduces your need to irrigate.
  • Leaf mulch helps buffer soil temperatures, keeping the soil cooler in summer and warmer in winter, which helps protect plants’ roots.
  • Leaf mulches can help to reduce soil erosion.
  • Mulching instead of raking and bagging eliminates the cost and environmental impact of plastic garbage bags.
  • Many species of butterfly and moth overwinter in leaf litter, either as eggs or pupae.
  • Mulched leaves are great for adding to your compost pile, being a source of ‘browns’ or carbon-rich material, which compost piles often lack.
  • Mulching eliminates the environmental cost of city pickup and the amount of yard trimmings that goes to landfills, extending their lifespan and saving tax dollars.

Potential Disadvantages of Mulching and How to Avoid Them

There are some potential disadvantages to mulching. However, we are here to give you ways to avoid most of these disadvantages.

  • You will have to mow as often as every four days, and if you will have to make multiple passes if you are using a rotary mower. However, this probably counts as less effort than raking or blowing leaves and checking when collection days fall.
  • Dried leaves produce dust and debris that can affect your eyes and breathing. For your protection, you should wear goggles and a dust mask.
  • Leaves of black walnut and eucalyptus contain natural herbicides that will stop seeds, including grass seeds, germinating. Make sure that you don’t mulch leaves from these species.
  • Pine needles also aren’t suitable, as they decompose too slowly and will smother your lawn. Pine needles will have to be raked or blown.
  • If you have a lot of trees, the mulched leaves may pile up too thickly and smother the lawn, preventing light and air from reaching the grass and the soil. Attach a bagger to your mower and put the mulch on your beds to act as a winter mulch for shrubs.
  • Excessive mulch can provide cover for burrowing pests such as voles. Make sure to remove the excess mulch.
  • Excessive mulch on the lawn can also prevent the grass from storing carbohydrates in the fall. Again, be sure to remove excess mulch; we provide tips on doing that.
  • Ash and maple leaves are more difficult to mulch than oak leaves, and you may need several passes to break them down.
  • The notion that oak leaves are acidic and will lower your soil’s pH is a myth, and a study by Michigan State University found that six seasons of mulching oak leaves into a lawn did not affect its pH.
  • If you have mulched correctly and your turf is still performing poorly, you may need to fertilize your lawn with fertilizer that benefits beneficial microbes.

When to Mulch Leaves

A few leaves on your lawn aren’t a problem, but excessive leaf build-up will block sunlight, limit air circulation, and keep the soil over-moist. The result is stunted growth and diseases such as snow mold.

If you can’t see the growing tips of the grass blades, or if the leaves cover more than a third of your lawn, you should mulch. A sudden cold snap may result in a massive leaf fall that you can leave for a couple of days until the yard is nearly covered, but don’t leave it any longer.

Don’t wait until it rains. Wet leaves don’t mow as easily and can clog collection systems.

How to Mulch Leaves Using a Lawn Mower

You can use a mower designed explicitly for mulching, which will simultaneously cut your grass, chop the fallen leaves into a fine mulch, and return the mulch to the soil. Or you can use a rotary mower, although you may have to make more than one pass.

If your lawnmower does not already have a curved mulching blade to churn the leaves into smaller bits, you can convert it. Buy a conversion kit from your local home improvement store or your mower’s manufacturer.

However, a mulching mower has curved, serrated mulching blades and baffling under the deck to circulate the shredded leaves (or grass clippings) several times so that it gets chopped finer.

The airflow under the baffling then pushes the finely chopped mulch into the surface of the lawn.

We recommend that you invest in a mulching mower if you have to process large quantities of leaves in a short period. Otherwise, an ordinary rotary mower should be sufficient.

If you are hesitant about getting yet another tool, know that you can use a mulching mower for regular grass cutting, too. The grass clippings will provide a natural 4-1-2 fertilizer to your lawn every time you mow.

Start the fall season with your mower on its regular height setting, and mow to your regular schedule. As leaves start to fall in earnest, raise your mower height to its highest, and mow once or even twice a week.

Shred the leaves into pieces around 1/2 inch in diameter or approximately the size of a dime.

Mulch to around 1/4 inch of mulch on the lawn so that the blades of grass are still visible and upright. The lawn may look slightly brownish for a few days; however, as the mulch breaks down, the lawn will return to a lush green.

If you have too much mulch, redistribute it from areas with a lot of mulch to areas with thinner cover, or collect it for use on your beds or in your compost. We recommend alternating mulching your lawn with mulching your beds.

There are various ways you can use your mulching mower for mulching leaves:

Side Discharge for Mulching Leaves

Use side discharge if the grass is tall and wet and the leaf cover is wet (or particularly heavy). You’ll either mulch the leaves into the lawn or shred them into fine particles for picking up later with the bagger attachment.

Mow in stripes to cut the discharge from the previous pass, or mow in concentric circles. Either way, you want to cut and re-cut the leaves.

Mulch Setting for Mulching Leaves

If the grass is of standard height and the leaves are dry or at most slightly moist, use the mulch setting.

Put the mulch plug into the mower and shut off the side-discharge port. Mow the grass, making a second pass at ninety degrees to the first to shred the leaves thoroughly and mulch them into the lawn.

Bagging Mulched Leaves

If the grass is of standard height and the leaves are dry, you can bag your mulch for disposal at the edge of your property or put it onto your shrubs for winter mulch.

Dump the mulched grass clippings and leaf particles onto a small tarp or into paper leaf-collection bags as you go.

The Features to Look for in a Mulching Mower

You will need the following features in a mulching lawnmower:

  • Self-propelled – lawn mowers are heavy, and when the bag is full of shredded leaves and grass clipping, it will be even heavier.
  • Rear-wheel drive – bags full of shredded leaves weigh down the back of the mower and cause the front wheels to lift so that they lose traction.
  • A powerful engine – it takes power to shred leaves. Invest in a mower with a powerful engine.
  • An aggressive high-lift mulching blade – a standard blade doesn’t move the air enough, nor does it have the serrations of a specialized leaf mulching blade. You can use a standard blade, but you will have to make many more passes.
  • A high-quality dust-filtering bag – not a substitute for wearing a dust mask, but an excellent dust-filtering bag will prevent the dust from swirling when you mow leaves.

Other Ways of Mulching Leaves

If you do not want to invest in a lawnmower suitable for mulching your leaves, there are various alternatives you can use.

To shred leaves with a string trimmer, fill a garbage can about three-fourths full of leaves, stick your string trimmer in and turn it on. Move it through the layers of leaves, keeping it away from the sides to prevent the line from breaking.

Be sure to wear protection for your ears and eyes when using this method.

You can also purchase dedicated leaf mulchers in handheld and stand-alone options.

A popular option is to use a handheld mulcher that you can use as a leaf blower or switch over to a leaf vacuum that shreds and collects the leaves in an attached bag for use as mulch. They might be powered by gas or battery power if cordless, or they might have an electric cord.

Stand-alone mulchers resemble a wood chipper and sit in one place in your yard. You will have to gather up the leaves, which is why we don’t recommend this option (more work), and then place the leaves into the hopper and let it shred them into the collection bag underneath.

Making Leaf Mold to Use as Mulch

Another way of mulching leaves is to make leaf mold.

Leaf mold is the soft layer of decomposing leaves found just above the soil in forests. As it slowly decomposes, it returns nutrients to the earth, improving the soil structure and feeding the plants.

It makes a great mulch around the garden and has an excellent water-retentive capability, holding anything from 300 to 500 percent of its weight in water.

To make it, construct a circular bin from chicken wire or snow fencing, add the leaves and dampen them. The leaf mold will be ready for use in the following spring or summer.

Final Thoughts

There are better things to do with a fall weekend than raking leaves. Incorporate mulching into your regular mowing schedule, and reap the benefits in free time and a healthier lawn.

You’ll save on plastic collection bags and help the environment too.

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