We’re so used to the autumn maintenance ritual of manicured gardens – the cutting, raking and bagging up of all the debris of spring and summer. While we have become habituated to do this, it’s important to remember that cleaning up the yard in this way makes it inhospitable for the butterflies, moths, bees, and toads on whom we rely to exist. Our yards and gardens are places capable of supporting a host of pollinators and other inhabitants. Removing spent material from the garden is removing fertilizer, rich topsoil, habitat, and food — or simply put, it’s gardening against nature.
Contemplate these facts as you consider how to maintain your garden this fall:
Native bees hibernate in a variety of ways in your garden. They may overwinter beneath burrows, and in spring they wake up and start constructing a brand new nest. Layers of mulch inhibit the queen bumblebee from building a nest. To encourage nesting bumblebees, leave some areas of bare ground in your garden. Don’t mulch where it is not needed. Leaf-cutter bees, mason bees and yellow-faced bees will nest in the hollow stems of many native plants. Leave your native plants standing over winter, and in the spring, instead of cutting them all the way down, leave 12 – 15 inches of stalk stubble standing for pollinator nesting sites.
Not all butterflies migrate in autumn. The swallowtails, cabbage whites and sulphurs form a chrysalis in late summer and hibernate, attaching themselves to the spent plant material of leaves and stalks. Mourning Cloak and Eastern Comma butterflies hibernate as adult butterflies in plant litter. The Baltimore Checkerspot, Meadow Fritillary and Red-Spotted Purple hibernate as caterpillars. In autumn, even though we don’t see it, next summer’s butterfly and moth populations are rolling up in the fallen leaves to hibernate. When we cut down and clean up our gardens, we are removing overwintering sites for butterflies.
A yard that’s been cleaned and left bare gives the birds good reason to fly on by. From a bird’s aerial perspective, a highly textured landscape signals a diversity of plants and better opportunity for food. The seed heads offer food to fall migrating birds and birds that stay for the winter. The standing, spent plants offer screening and a safe place for the birds to forage. In spring, the extra plant material means that there are more insects, and more worms. Your native plants provide the right material, the right environment, and the right nutrition, just when the birds need them.
Toads overwinter in spent plant material or deep down in loose soil, protected by the plants. When they emerge they constantly consume insects, snails and slugs. To encourage toads, you can offer safe winter retreat areas by stacking up rocks and leaving a toad-sized space beneath them. Situate the hibernation spaces under a bush, or any insulated and protected spot in your yard.
So we see that plenty of creatures overwinter in garden litter, from queen bumblebees to mourning cloak butterflies to black swallowtails to all manor of frogs, spiders, beetles, and bugs. Inside plant stems may be larvae of native bees, since roughly 25% of native bee species use cavities found in wood or stone as nesting sites. The spent plants, and the snow they gather, also adds a layer of insulation that protects the plant roots from harsh winter winds and frigid temperatures. This is one reason why, in early to mid spring, you should leave 12-18 inches of stem when cutting back the garden — you will soon see swarms of bees coming to lay eggs in hollow stems or to excavate pith before egg laying begins. After a few weeks the “ugly” dead stems will soon be covered by new green
Seed heads are important food sources for birds, and offer you as a gardener the opportunity to feed the birds and share the bounty of more plants with your gardener friends. You can:
1. Let them grow – some plants have shorter lives than others, and the self-seeded plants will replace the old ones.
2. Remove some of the seedlings, and leave others to grow and fill-in as needed. Move the new seedlings to a different location entirely or pot them up and share them with friends.
3. Some plant species are abundant self-seeders that can be difficult to keep up with. If this is the case remove most of the entire seed head from the species and place them in an area where they are less likely to overwhelm your garden, while still being available to the birds.
Native plants are beautiful in all seasons – let them play their part in bringing your landscape to life. “Leave the leaves” and let your native plants stand through the winter. Allowing spent plant material to remain in the garden is one of the simplest and easiest things that we can all do to promote biodiversity in our landscapes. Understanding the important environmental role of the spent plant material is the first step.
So the next time you think about heading out with pruners in hand, think again about the life that depends upon those plants. As entomologist and author Doug Tallamy so eloquently says:
The responsibility for our nations biodiversity lies largely with us.
Resources:
‘Meaningful Maintenance: Fall Clean-up with a Positive Impact’ (Nativeplantherald.prairie nursery.com)
‘Bringing Nature Home: How You Can Sustain Wildlife with Native Plants’ Douglas W. Tallamy, Timber Press, 2009
Friends of the Greenhouse Inc. 