Yard and Garden: Managing Fallen Leaves

Each autumn the leaves on the deciduous trees in our yards fall into lawns and garden beds. Collecting and removing every leaf is not necessary but simply ignoring them isn’t a good option either. Iowa State University Extension and Outreach horticulturists offer advice on how to manage the colorful blanket of leaves that appear in your lawn and garden each fall.

Can I just leave fallen leaves on my yard and garden?

Leaving the leaves alone is a good way to support native pollinators and other insects and wildlife. These valuable insects rely on the habitat fallen leaves provide, especially over the winter months. Dead leaves also decompose, creating compost that can improve soil structure and fertility. Even with all these benefits, it doesn’t mean that leaves can simply go unmanaged in the lawn and garden. If nothing is done, layers of fallen leaves can cause damage by blocking out light and smothering plants, which can kill them. Often a little redistribution of the leaf layer to prevent a thick mat of leaves from forming is all that is needed to prevent this type of damage. 

Excessively thick layers of leaves (greater than 6 to 8 inches) may need to be reduced or removed. Whenever possible move them to mulched garden areas with fewer leaves or create a compost pile onsite to keep all that beneficial organic matter in your yard.

Do I have to remove the leaves from my lawn?

Turfgrass plants utilize light, water and nutrients to manufacture food. In the fall, lawn areas beneath large trees are often completely covered with leaves. The leaf debris prevents the turfgrass plants from manufacturing and storing food prior to winter and can block light causing areas of the lawn to dieback, leaving behind patchy areas of dead grass that are unsightly and more prone to weeds.   

A layer of leaves where little or no grass is visible will need to be managed. Leaves can be collected by raking, blowing or using the collection bag on a mower and then removed from the lawn and added to a compost pile or sent to a composting facility. Gardeners can also manage leaves on the lawn by mowing. Chopping the leaves up with a mulching mower can help return organic matter to the soil, benefitting the lawn, and for most people, it is easier than raking and removing. The leaves must be chopped into pieces small enough to fall down between the blades of grass. When finished, very little leaf debris should be visible. Mowing is best done when the layer of leaves is thin and dry, so mow often throughout the fall. If the leaf layer is thick, mow over an area more than once. 

What do I do with fallen leaves in my flower beds?

Leaves are an excellent resource for the garden. They break down to add organic matter and nutrients to the soil. As they decompose, they act as a mulch, suppressing weeds and helping to maintain consistent soil moisture. Additionally, they can help insulate the ground over the winter, protecting perennials from extreme cold temperatures.

For the most part, leaves in perennials beds, under shrubs and in other mulched areas do not have to be removed. Even thick layers of fallen leaves will break down over the winter leaving you with an inch or two of mulch the following spring. It is beneficial to keep a thick mat of leaves from forming over the crowns of perennial plants. Keeping leaves off evergreen perennials, such as creeping phlox (Phlox subulata) and Lenten rose (Helleborus), and away from the base of shrubs and trees is also beneficial. This may require some redistribution of the leaves from areas that have thick leaf layers to other garden areas that have fewer leaves.

How do I dispose of leaves that I collect?

If fallen leaves are collected, there are a several options for what you can do with them. Whenever possible, keep this valuable organic resource on-site. Leaves can be added to a compost pile to create “black gold” to use in your garden to improve soil structure and add fertility to the soil. Leaves can be composted whole or shredded to allow them to break down and create compost faster. 

Even without a compost pile, leaves can be piled in a back corner of the garden to produce leaf mold. Leaf mold is partially decomposed leaf matter and can be used like mulch throughout the garden. A pile of leaves around 3 foot tall and wide will transform into leaf mold over a period of one to two years. Shredding the leaves allows it form faster. 

If composting in your own garden is not an option, leaves can be bagged and sent to a city or commercial composting facility. Avoid the use of plastic bags and never send leaves to the landfill.

Burning leaves is another option, but not typically a desirable one. Many of the beneficial nutrients found in fallen leaves are lost when burnt. Burning leaves releases irritants and particulate matter into the air that can pose health risks. In some municipalities burning leaves is illegal. Additionally, burning leaves can be dangerous if not done properly. When conditions are too dry or windy the fire can quickly burn out of control resulting in property damage and costly fines.

Shareable photo: Leaves in lawn.