Leave the Leaves for the Butterflies and Bees

Some look askance at my piles of leaves up against the front fence, or blanketing portions of my yard or parking strip in the fall.  After all, we're taught that raking up the leaves and either bagging or burning them is right thing to do here in Baker City. There are many critters hoping you won't though, because they need them for home insulation to get through the long and frigid winter.

The Xerces Society sent out a reminder of their "Leaves the Leaves" campaign today explaining just why the Bees and Butterflies will be grateful if you do, and they asked that the information be passed along, so here are their two articles on ways to help out.

Leave the Leaves!

Besides providing the right plants, and protecting your garden from pesticides, one of the next most valuable things you can do to support pollinators and other invertebrates is to provide them with the winter cover they need in the the form of fall leaves and standing dead plant material. Frequently however, this is the hardest pill for gardeners to swallow.
It may be habitual, a matter of social conditioning, or a holdover of outdated gardening practices from yesteryear – but for whatever reason, we just can’t seem to help ourselves from wanting to tidy up the garden at the end of the season – raking, mowing, and blowing away a bit of nature that is essential to the survival of moths, butterflies, snails, spiders, and dozens of arthropods.
That’s why this year – and every year – we are making the case for leaving the leaves and offering input on what to do with them. Read on!

Most love leaves

The red-banded hairstreak is one of many butterflies that depend upon leaf litter as part of their life-cycle. Photo by John Flannery / Flikr

While monarch migration is a well-known phenomenon, it’s not the norm when it comes to butterflies. In fact, the vast majority of butterflies and moths overwinter in the landscape as an egg, caterpillar, chrysalis, or adult. In all but the warmest climates, these butterflies use leaf litter for winter cover. Great spangled fritillary and wooly bear caterpillars tuck themselves into a pile of leaves for protection from cold weather and predators. Red-banded hairstreaks lay their eggs on fallen oak leaves, which become the first food of the caterpillars when they emerge. Luna moths and swallowtail butterflies disguise their cocoons and chrysalis as dried leaves, blending in with the “real” leaves. There are many such examples.
Beyond butterflies, bumble bees also rely on leaf litter for protection. At the end of summer, mated queen bumble bees burrow only an inch or two into the earth to hibernate for winter. An extra thick layer of leaves is welcome protection from the elements. There are so many animals that live in leaves: spiders, snails, worms, beetles, millipedes, mites, and more – that support the chipmunks, turtles, birds, and amphibians that rely on these insects for food.
It’s easy to see how important leaves really are to sustaining the natural web of life.

Leaves and Lawn

According to a 2005 NASA estimate, there are around 40 million acres of lawn in the continental United States – making turf grass the single largest “crop” we grow. This disproportionate ratio of lawn to garden is the main reason we rake, mow, and blow. To mimic the natural ecosystem an animal needs, a layer of leaves needs to be at least a couple of inches thick.  While this would be too much of a good thing for turf grass to handle – research has shown that lawns actually benefit from a thin layer of leaves, and the rest can be piled up around ornamental trees, shrubs, and perennials to no ill effect.
If you must keep your lawn clear of leaves – try opting for raking or using a leaf vacuum to capture whole leaves, rather than shredding them with a mower and make a leaf pile in a corner of your yard. More on that below.
Better still would be to reduce your overall lawn footprint, replacing it instead with wildlife supporting plantings that can be future repositories for fall leaves.
To shred or not to shred
Many organic gardeners opt for shredding their fall leaves for use in compost piles. While this is certainly a more environmentally friendly practice than bagging leaves and sending them to the landfill – shredded leaves will not provide the same cover as leaving them whole, and you may be destroying eggs, caterpillars, and chrysalis along with the leaves. We suggest that leaves in garden beds and lawn edges be left whole. Where space allows, consider creating a leaf pile and allowing it to break down naturally, or add the leaves gradually to your compost pile over time. Such efforts will keep critters safe and allow you to benefit from the rich garden gift that falls from the trees above.

Fallen leaves have all the properties and benefits of expensive wood mulch – and they’re free! Photo by The Xerces Society / Justin Wheeler

Free mulch!

Another reason to leave the leaves is for the many benefits they provide to your landscape. Leaves provide valuable organic matter and build up healthy soil. Fallen leaves have the same weed suppression and moisture retention properties of shredded wood mulch – and they’re free! Where mulch is desired as a decorative element, what could be more seasonally appropriate than a pile of brightly colored fall leaves?
In the past gardeners may have worried that fall leaves, matted down by snow or rain, would have a negative impact on their perennials. In reality, a thick layer of leaves provides additional insulation against bitter cold weather, and can protect newly planted perennials when frost-heave may expose tender roots. Anyone who has spotted fragile spring ephemerals popping up in the woods knows that all but the frailest of plants will burst through the leaf litter in spring without trouble.

The bottom line

You gave them flowers and a place to nest. You tended your garden and avoided pesticides. Don’t carry all of that hard work out to the curb. Simply put, when we treat leaves like trash – we’re tossing out the beautiful moths and butterflies that we’ll surely miss and work so very hard to attract.
While the idea is to “leave the leaves” permanently – for all of the benefits mentioned above – if you do decide you need to cleanup the garden and remove the leaves in spring, make sure you wait until late in the season so as not to destroy all the life you’ve worked to protect.

The article above was written by Justin Wheeler, Web Manager and Communications Administrator, Xerces Society.

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Here is the second article offering tips on how to help turn your yard into helpful habitat for bumble bees and other pollinators.  For help on identifying bumble bees found around Baker City, and seeing some of the plants they like to visit, see my bumble bee album on Flicker. In my yard, the bees love Agastache (mustang mint), Monarda, Penstemon, cat-nip, sunflowers and similar plants (composites in the family Asteraceae), fire weed, goldenrod, and asters in the fall. Some like roses as well. And oh--leave some dandelions for early spring food needed by emerging bumble bee queens! Nepeta and self-heal are good for early spring food too.

Fall Garden Tips to Benefit Bumble Bees All Year

The growing season may be winding down, but fall is an important time to create habitat for bumble bees and other native pollinators. The work you do now will help support overwintering pollinators and support the next generation of bumble bees.

Creating Fall Bee Habitat

As a start, consider leaving some “natural chaos” in the spaces you manage, such as newly fallen leaves, branches and logs, and loose dirt. These elements benefit overwintering queens that need insulation (that’s what the leaves are for), and materials to build their overwintering sites (rotting logs and loose dirt).
In this vein, the Xerces Society launched the Leave the Leaves campaign last year, and it is still going strong. The Leave the Leaves campaign encourages homeowners to not only leave their leaves, but also provides ideas on beneficial ways to incorporate them into the landscape. We also recommend creating brush piles and keeping grass tussocks and fallen logs, to help create both overwintering habitat and nest sites. Simple steps like these provide natural habitat for overwintering bumble bees and a host of other beneficial insects. We all will be reaping the rewards in the spring and beyond!

Using Bumble Bee Watch Records to Guide Plant Choice

Depending on your region, fall can be a great time to install new habitat that will support foraging bumble bees next season. Careful planning now can make a big difference when bumble bees need food the most: when they first emerge from hibernation, and food sources are limited. Having floral resources available in early spring is especially important for early-emerging queens as they establish their colony. Putting these plants in the ground now will ensure they are blooming and ready for bumble bees when they wake from their winter slumber.

For guidance on bumble bee habitat needs and their preferred forage plants, in addition to the many printed plant lists available from Xerces and other sources, we’ve searched Bumble Bee Watch for some bumble bee specific recommendations. The observations in Bumble Bee Watch provide evidence based insight into the needs of different bumble bee species and therefore can help us to create habitat that supports common and rare bumble bees alike.

Early-season flowering shrubs such as rhododendrons are important food sources for bumble bees as they awaken from their winter slumber. (Photo: Xerces Society / Matthew Shepherd)

Bumble Bee Watch records also help to shed light on common early season food plants for bumble bees, and provide information on seasonality of foraging resources. For instance, early-season shrubs like rhododendron, azalea, and willow provide floral resources as soon as bumble bees emerge and help early-emerging species to establish a successful nest. In the west, yellow-faced bumble bees (Bombus vosnesenskii) and black-tailed bumble bees (B. melanopygus) rely on resources of this sort, as does the common eastern bumble bee (B. impatiens) in the east. Other early season shrubs and trees that bumble bees are documented as visiting on Bumble Bee Watch include Ceanothus spp. (California lilac or New Jersey tea) and various apple varieties (Malus spp.). Nearly 20 species of bumble bees have been observed visiting these plants, including rare bumble bees like the western bumble bee (B. occidentalis) and the yellow-banded bumble bee (B. terricola).

While early shrubs and small trees are essential for queens starting a nest, the colony will also need food continually through fall. Although considered primarily as host plants for monarch caterpillars, milkweeds (Asclepias spp.) are a great mid-season native perennial that provide abundant nectar for pollinators, including bumble bees. Records from Bumble Bee Watch suggest this plant supports many different species of bumble bees including four rare bumble bees: Crotch’s bumble bee (B. crotchii), western bumble bee, and Morrison’s bumble bee (B. morrisoni) in the West and the rusty patched bumble bee (B. affinis) in the Midwest. In addition to these four at-risk bumble bees, Bumble Bee Watch records on milkweed include 21 species from 29 U.S. states and 6 Canadian provinces. It is important to focus on species of milkweed that are native to your area. In that vein, please note: Tropical milkweed should not be used. Please see Tropical Milkweed: A No-Grow for more information. Planting native species of this celebrated monarch host plant in your landscape will benefit a diversity of pollinators!

Asters are an important late-season pollinator resource. Pictured: Great northern aster (Canadanathus modestus). (Photo: Xerces Society / Matthew Shepherd)

Late-flowering species in the aster family such as goldenrod and asters provide forage into September and October. In fact, these are some of the most frequently visited flowers according to Bumble Bee Watch records, with almost 700 records on goldenrod (Solidago spp.) and nearly 450 observations of bumble bees on asters (Symphyotrichum spp.). The records for these two plants come from 24 U.S. states and 9 Canadian provinces, with at least 26 different bumble bee species visiting them, including rare species like the western bumble bee, the yellow-banded bumble bee, and the rusty patched bumble bee.

Once common throughout much of the east, the rusty patched bumble bee has been lost from most of its range, and is now listed as endangered by the U.S. Fish and Wildlife Service. For those who live in its former range, we highly recommend utilizing Bumble Bee Watch’s data to help build habitat in support of this imperiled species. Of 371 verified Bumble Bee Watch records of this at-risk bumble bee, over 50 percent have been recorded visiting beebalm (Monarda spp.), giant hyssop (Agastache spp.), goldenrod (Solidago spp.), and joe-pye weed (Eutrochium spp.). Of course, we can’t promise that these plants will be successful in attracting rusty patched bumble bees to your property, but if they do show up, we know they will appreciate these floral resources. The upshot is that many other pollinators (including monarchs and other bumble bees) will benefit from these flowering plants, too!

The rusty patched bumble bee (Bombus affinis) was once common throughout much of the east, but now has been lost from most of its range and is listed as endangered by the U.S. Fish and Wildlife Service. We encourage those who live in its range to plan plantings to support rusty patch populations. (Photo: Xerces Society / Rich Hatfield)

With over one-quarter of bumble bee species on the decline in North America, it is increasingly important to find ways to support these important pollinators. Protecting, creating, and restoring habitat in a diversity of landscapes is critically important to conserve remaining populations of bumble bees from the threats they face. To help researchers learn more about bumble bees and to contribute to their conservation, please consider joining Bumble Bee Watch to participate in this continent-wide effort, and to contribute to this invaluable source of information.

If you live in the Pacific Northwest, your observations can also help to put bumble bees on the map in Idaho, Oregon, and Washington—thanks to a coordinated effort by the Washington Department of Fish and Wildlife, the Idaho Department of Fish and Game, the Xerces Society, Oregon State University, and the Oregon Department of Agriculture. The Pacific Northwest Bumble Bee Atlas aims to understand more about bumble bee distribution and the habitat features that are important to them across the region. Please stay posted as we ramp up for another season of the Atlas project in early spring 2019.

Although many of us, wherever we live, will have to wait until spring for the buzz to return to our landscapes, right now we can sow the seeds that will support bumble bees in our gardens next year. We encourage you to do your part to support the life that sustains us.

(Please note: floral species are not verified on Bumble Bee Watch, thus we are dependent on the knowledge of the contributors that listed these plants as the host plant of the visiting bumble bee.)

The article just above was written by Michele Blackburn, Endangered Species Conservation Biologist, and Rich Hatfield, Senior Endangered Species Conservation Biologist and Bumble Bee Lead