Raking leaves is a standard of fall chores, but in recent years the need for it has become more of a debate. Are fallen leaves really causing harm being left where they lie on the lawn or garden? Or do they provide much needed nutrients and organic matter for other plants? The answer is usually somewhere in the middle and as always, dependent on the specific situation.
Leaves on the lawn might be the greatest cause for concern because heavy leaf cover can kill the grass underneath. Heavy leaf cover kills grass by blocking light in the same way that putting a tarp or sheet of plastic over a section of lawn kills the grass beneath. Heavy leaf cover may also hold excessive moisture and humidity, creating a more favorable environment for turf disease development in winter and early spring.
There are a couple of options to prevent leaves from smothering grass besides raking. The easiest and arguably most beneficial way to get rid of heavy leaf cover is to mulch leaves with a mower. Use a mulching mower or a regular one. The important thing is that the leaves get chopped into small enough pieces to fall between the blades of grass rather than sit on top of them and block out light.
A Michigan State study published in 2010 suggested that mulched leaves could provide some pre-emergent dandelion control. Mulched leaves also return nitrogen and other important nutrients to the soil, which benefits the grass or other plants growing there. Finally, the mulched leaves are what horticulturists refer to as organic matter — broken-down plant material (or material in the process of breaking down). Organic matter benefits the soil by improving air and water movement and increasing beneficial microbial activity.
The only downside to mowing leaves to mulch them is that it may mean mowing frequently. But, the practice is good for the grass too and still less work than raking.
The second option for leaves on the lawn is to use a bagging attachment on the mower while mowing over them. This is the best option when the amount of leaves on the lawn is excessive even after being chopped up with the mower, or for leaves that break down very slowly like some species of oak. Some leaf pieces will still fall onto the lawn, but the excess is removed for use in another area of the yard. Collect bagged material in a compost bin, mix it into the vegetable garden or a new landscape bed, or use it to mulch tender perennials and shrubs.
The last option for leaves that cover the lawn is to remove them with a blower or leaf rake. Collected leaves can then be chopped in a chipper/shredder and used as above, or simply used whole as described above, if layered in carefully. If leaves are plentiful and uses are limited, send the extra leaves to the community compost pile so you or someone else can use the composted version next year.
Gardens and landscapes
For fruit/vegetable gardens and landscapes, there is only one reason to remove leaves in the fall. If leaves completely cover a plant that is still photosynthesizing they should be removed. Leaf removal can simply mean raking them off a plant or away from it — perhaps into the lawn where the leaves can then be chopped by the mower. Otherwise, leave the leaves. They are good for the other plants.
If you do choose to rake, remember that the activity can be a serious workout. Stretch before and after the chore. Wear gloves to prevent blisters. Switch sides and change hand positions frequently to reduce fatigue. Take care when lifting heavy bags or tarps full of leaves.
— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation.