Why to Leave Your Leaves

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Every fall, as our trees and shrubs begin preparing for their winter sleep, we watch leaves morph from green to yellow (or orange on our Basketbush Sumac and Japanese Maple). Soon after, each leaf lets go of its supporting branch and drifts down to earth. Piles of fallen leaves collect along our pathways, porches, and patios. But we don’t see this annual event as more work to do in the yard — because we never move the leaves any farther away than off the porches and decks with a broom. We know how valuable these leaves are to the health of our yard, and we are excited to watch the cycle of rebirth they are entering.

Plants that go dormant in winter are closing down the sugar factories before frost would freeze the water inside each leaf, which would cause cells to burst and lose all the hard-won nutrients inside — not to mention killing the leaf tissues. After sending all the precious sugars and nutrients from leaves down into the roots for winter storage, the branches snip off each leaf with a special acid, closing the door on the scar with a cork-like covering. You might think the role of the leaf is over, but it still has a vital task to perform for the plant — and for the landscape around it.

Just like a warm blanket against the cold, fallen leaves help to insulate the ground around plant roots from chilling weather. As the leaves slowly decompose, they liberate their remaining nutrients into the soil, while providing food for many beneficial fungi, bacteria, insects, and a host of tiny organisms. This team of soil creatures transforms the decaying leaves’ nutrients into usable food waiting for roots when their dormant plants wake up in spring. These soil magicians ultimately convert the dead leaves into valuable mulch, which helps to retain precious moisture in the soil throughout the coming dry seasons.

This important saga in the life-cycle of fallen leaves not only benefits deciduous plants (those that lose their leaves in winter), it also benefits nearby evergreen plants. Even though evergreens have mechanisms to withstand freezing (including a plant version of anti-freeze), evergreens profit from the work that deciduous leaves have accomplished in their death: contributing fertilizing nutrients, soil-insulating properties, and soil-moisture-saving paybacks. Evergreen and deciduous plants alike also benefit from the weed-deterring job carried out by a blanket of fallen leaves.

So the next time you think about hauling off your piles of fall leaves, remember the role these heroic leaves still want to achieve in your yard. Put down your rake, and enjoy the rhythm of the leaves.

 

 

 

 

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