Why It’s Good to Leave the Leaves

Fall leaves on grass

Fall leaves are a valuable resource, useful for replenishing a lawn or garden. And they’re free!

When trees drop their leaves each fall, homeowners are conditioned to rake or blow them away as soon as possible. Then the piles are burned, collected by municipal trucks, or left to rot in a neighboring wooded area. Few people view this annual leaf drop as a plus. However, leaves decompose to benefit plants and the soil, making them a valuable – and free – resource instead of “nature’s trash”.

Why Treasure Dropped Leaves: Fallen leaves are an organic powerhouse. They are one of the main ingredients that Nature uses to create soil. When leaves from trees and shrubs drop and decay, they add nutrition and organic matter gradually to the soil. They provide a natural blanket or mulch that insulates the plants over winter, and are especially valuable on top of soon-to-be-dormant perennial flower beds. The combination of fallen leaves, grass clippings and/or spent plants from the yard makes the perfect recipe for homemade compost – the best antidote to lousy soil (be sure that weeds have not already gone to seed before composting). Leaves are such a valuable resource that avid/zealous gardeners have been known to gather leaves from others’ curbs.

What to Remove: Allowing the leaves to remain makes far more sense than trying to remove every last one – in most places. But leaves on hard surfaces such as driveways, sidewalks, and roads, for example, serve no useful purpose; that’s one place to blow them or bag them. Leaves that are diseased are best removed too – to the trash or at least out of the area containing plants susceptible to that disease. Disease spores often overwinter in leaf litter, where they’ll re-infect susceptible plants the following year, as soon as rain comes. A third potential removal area is on evergreen groundcover beds, such as vinca (Vinca spp.), ivy (Hedera helix & spp.) and Japanese pachysandra (Pachysandra terminalis). Thick piles of leaves here shut off sunlight, stunt growth, and may even kill these plants. A thin leaf layer, an inch or less though, is a different story. Light coverings of leaves over groundcovers usually decay and work their way into the ground before causing trouble.

Other Strategies: On lawns a better solution is to simply run over the leaves with a mower, rather than raking or blowing small amounts of them. Chopped into bits, those leaves become fast-decaying mulch that adds organic matter and nutrition to feed the grass. Unless the layer is very thick, chopped leaves don’t cause thatch as many people think. University researchers have compared lawns in which leaves were mowed in vs. raked off, and the leaves-on lawns came out healthier and better performing. For those who like their lawns neat, run over the leaves twice to double-chop them, and cut often enough to ensure the amount per cut is manageable.

Unless the amount is huge, leaves that fall and/or blow into shrub and perennial beds or around trees can stay. They’ll insulate over winter and decompose enough by spring that they perform the same job that purchased piles of mulch do. Given that this is free fertilizer and free mulch, it makes little sense to buy a rake or blower to move leaves to the curb, then pay municipal taxes to have the piles hauled away, and then buy bags of fertilizer and mulch in the spring. If you don’t like the look of fallen leaves in beds, in spring top the existing leaf layer with a light dressing of wood mulch or bark chips. That’ll give the “clean” look that so many “yardeners” relish.

Even in areas where leaves should be removed or thinned, think about recycling them on site. Instead of raking or blowing away leaves, relocate them to tree and shrub beds (preferably chopped), chop and use them as mulch for vegetable or flower beds, add them to the compost pile, or bag and keep some as mulch around next year’s vegetable and flower plants.

Mowing leaves

In fall, don’t rake leaves — mow them. A mulching mower can chop leaves into bits which form a fast-decaying mulch that feeds the grass.

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