Should You Leave Leaves in Flower Beds Over Winter?

Raking leaves is a tedious chore best forgotten. Fortunately for us, environmental groups and gardening experts alike are telling us to just leave them where they fall in our gardens. But can you really just forget fall cleanup and leave those leaves in your flower beds?

Should You Leave Leaves In Flower Beds Over Winter?

Yes, you should leave fallen leaves in flower beds over the winter. A layer of leaves will protect beneficial insects, beneficial microbes, perennial plants, and bulbs. Leaves decompose to return nutrients to the soil. Keep leaf buildup from smothering growing plants and evergreens. Remove leaves from a diseased or pest-ridden tree.

Leaving fallen leaves in your flower beds over the winter has a lot of benefits, including:

  • Protecting bare soil from erosion,
  • Protecting beneficial insects and microbes in the soil,
  • Protecting overwintering beneficial insects in leaf litter,
  • Protecting bulbs and perennial plants, and
  • Returning nutrients to the soil as they decompose.

However, plants still need light and air circulation, especially those still growing in the fall or evergreen plants that grow through the winter. If the leaves pile up so high that you can’t see the plant, then you need to uncover the plants and move the extra leaves somewhere else.

For extra assurance or if the leaves are very big (like a sugar maple), you could mulch the leaves into smaller pieces. Mulched leaves break down faster, so it’s better to mulch leaves for compost.

But mulching leaves also means that you’re destroying any insects that are using the leaf litter for winter cover or to lay their eggs (including many beneficial insects like ladybugs). Moving these leaves somewhere else on your property can keep these beneficial insects safe while also not smothering your plants.

When should you remove leaves from flower beds?

For the most part, you won’t need to remove leaves from flower beds. But there’s a few cases where you will want to, like if the leaves have piled up too high (removing just the excess), if the leaves are diseased (more on that below), or you’re sowing seeds.

If you have a Black Walnut tree, remove any Black Walnut leaves from any garden beds with non-resistant plants in them. Black Walnut leaves in the fall have less juglone than spring leaves, and considerably less than roots, but they still contain juglone. Throw Black Walnut leaves into a well-managed compost bin instead. By the time the compost is ready, the juglone should be gone. You could be fine with leaving the leaves in place if they decompose quickly enough, but composting is faster and safer.

Should you remove leaves from flower beds in spring?

You don’t have to remove leaves from flower beds in spring, so long as they’re not smothering the plants there. If you’re planting new annual seedlings, you can even just gently move the leaves while planting before returning them around the new plant. If you’re starting from seed, then keep the leaves off the soil around the seed until they can sprout.

Spring bulbs should be able to push up through leaf litter by themselves, or even a layer of bark mulch. If the leaf layer is still very thick, you can gently rake them away from where the bulbs will come up.

If you normally mulch your garden beds, you don’t need to remove the leaves first. You can just mulch on top.

If you decide to remove leaves or mulch in the spring, wait until daytime temperatures consistently reach 50F (10C). This gives beneficial insects enough time to wake up or hatch from under leaf litter and the soil. Meanwhile, you still have a layer of mulch in place, so you get the benefits of mulch or a ground cover without accidentally blocking exits for insects overwintering in the soil by applying mulch too early.

Will leaves decompose over winter?

While the cold will slow down or stop decomposition, a thick layer of leaves (4+ inches) can still break down to a thin layer (1 – 2 inches) through the winter. Leaves also have the benefit of the shoulder seasons, when it’s too cold to do anything in the garden but warm enough for decomposition to pick back up. Leaves add a layer of insulation, so decomposition can happen even when you can’t see it. And when spring arrives, your soil is still covered and protected by the remaining leaves.

Even in the best conditions, leaves take longer to break down. Some species are faster than others, depending on their lignin content.

Can you have too many leaves in garden soil?

Technically, if you bury leaves, you can have too many leaves (or carbon sources) in your garden soil. If there are too many leaves and not enough nitrogen sources, then the leaves will lock up available nitrogen in the soil to decompose. There won’t be enough nitrogen available for growing plants.

But the fix is easy. Just don’t bury leaves in your garden soil. Leave them on top of the soil, where they don’t have access to most of the nitrogen and can give you all the benefits listed above.

If you still want to bury them, then bury them with enough nitrogen sources (like kitchen scraps) to make up the balance.

A few leaves accidentally getting into a planting hole or getting churned up when rototilling won’t make much of a difference, so don’t worry. You’ll only have problems when you’re burying a lot of leaves.

Do fallen leaves harbor pests or diseases?

Like most natural gardening, using fall leaves as mulch is a double-edged sword. Fall leaves protect pests as much as they protect beneficial insects.

If the source tree has been infected with a disease or with pests, then play it safe and remove the leaves from your garden.

Otherwise, just make sure the leaves aren’t smothering your plants, work to attract beneficial insects, and improve beneficial microbes in the soil. Balance is key. If you have enough beneficial predators, they’ll keep pest populations in check. Likewise, healthy soil helps plants be healthy, and when plants are healthy, they resist diseases better.

Final Thoughts

Fall leaves can be a great ally for the health of your flower beds. By leaving them in place, you’re mimicking nature and protecting your plants, beneficial insects, and beneficial microbes. Just make sure that the leaves don’t build up high enough to block out evergreen or still growing plants, and don’t bury them in your soil.

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