How to Build Habitat for Beneficial Garden Insects in Fall
As the active growing season winds down in the fall, we have the opportunity to support beneficial insects through our end-of-season gardening. Extended flowering, natural leaf drop, and other natural resources provide a foundation for successful overwintering of the essential inhabitants. Gardening expert Katherine Rowe explores how to boost beneficials in the fall for a balanced garden system.
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Fall is rife with opportunities to promote habitat for pollinators and insects with beneficial garden roles. Simple measures make it easy to foster our essential garden visitors and inhabitants.
Beneficial insects work to boost yields by pollinating food crops and ornamentals. They balance the garden through natural pest control, as predators and parasites of common insects that feed on plants. They also increase the local food web as resources for birds, reptiles, and amphibians.
Fall is a prime time for adding to our collections with a diversity of plants that support hard-working insects. It’s also a time for selective tidying, rather than a clean sweep. Follow these steps to build a habitat for your garden’s fall beneficial insects.
Our Insect Inhabitants
The fall landscape is an important habitat for native bees, butterflies, moths, hoverflies, parasitic wasps, beetles, and more, as they prepare to overwinter. Fall beneficial insects pollinate our blooms and crops and prey on pests like aphids, Japanese beetles, and spider mites.
They nest, lay eggs, and seek shelter in fallen leaves, hollow stems, and loose bark. Amphibians, invertebrates, songbirds, and small mammals also seek refuge from cold weather in the shelter of standing plants, logs, brush piles, stone walls, leaf litter, and healthy soils.
Insects that inhabit our gardens in fall and winter include:
- Queen bumblebees
- Fireflies
- Fritillaries
- Ladybugs
- Leafcutter bees
- Luna moths
- Red-banded hairstreaks
- Swallowtail butterfly caterpillars
- Woolly bear caterpillars
Add Nectar and Pollen-Rich Selections
Fall is optimal for planting and expanding our collection. Pollen and nectar-rich plants that bloom throughout the season draw native bees and many others. Planting now sets the foundation for next season’s biodiversity and beneficial insect support.
In the season’s moderate conditions, plants establish strong root systems to survive winter. We may also get a final round of blooms from added selections that show color until frost.
Plant new trees, shrubs, flowering perennials, and herbs four to six weeks ahead of fall’s first anticipated frost date. This timing lets roots settle in and develop before freezing conditions. Direct sow perennial seeds post-frost. Those that need cold stratification, like many of our favorite natives, receive plenty of chill exposure for germination in the spring.
Native plants are a hallmark of insect-supporting arrangements. They have specific attributes that match the needs of native pollinators, and they adapt to their growing environment without requiring extra resources. The USDA has an interactive plant search database that identifies site-specific native plants and their associated insects.
Pollinator-favorite native plants include aster, blazing star, milkweed, rudbeckia, and penstemon.
Diversify Flower Shape
A variety of floral shapes and forms ensures that insects have access to nectar for energy and pollen for protein. From tubular blooms with nectar-rich centers to flat-petaled ray flowers with prominent open centers, a combination provides broad appeal.
Various shapes also provide spots for pollinators and other fall beneficial insects to land, rest, and take shelter from wind and rain. Perennials with large, flat flowerheads like yarrow become landing pads, and cupped or bell flowers like poppies and foxgloves offer a spot to nestle in and rest.
Go for Color
Diving deeper into the fascinating world of fall beneficial insects and their relationship to flowering plants reveals their penchant for color. Specific colors attract different species, depending on their cone of vision.
Yellow and purple flowers are especially attractive to butterflies. Purple, blue, and yellow are in the bee’s sight line (though this doesn’t mean they won’t visit other blooms). As with floral forms, a range of colors gives the most opportunity for repeat visits.
Extend the Bloom Season
When selecting plants for beneficial insect support, consider those with an extended flowering season. Aim for staggered bloom times for early and late pollen and nectar sources. Those early to show color in spring and those with a flush in fall provide food reserves to correspond to emergence, migration, and overwintering.
Avoid Bare Beds
From dormant perennials to cover crops, existing vegetation plays an important role in raised and in-ground beds during the winter. Instead of leaving beds empty, consider a cover crop or organic mulch cover to build soil and habitat.
Cover Crops
If you have a bare bed to hold until spring, specialized cover crops help improve and nourish the site. Cover crops like fall-planted grasses and legumes enrich soil between primary crop-growing phases.
Cover crops are quick and simple to sow and improve growing conditions in the long term. They suppress weeds, build soil nutrition, and support pollinators with flowers in transitional seasons.
Scatter cover crop seeds generously to prepped beds. Choose cold-hardy varieties for your USDA growing zone, or opt for a quick cover to die back with heavy frost. Cut the transitional crops back after they flower but before they go to seed, leaving the cut material in place or adding it to the compost pile. Let it become organic mulch by folding them into the soil or seeding directly into the leftover material.
Mulch
Topdressing with mulch is another way to build habitat instead of leaving beds bare. Leaf litter and leaf mold provide a natural mulch from fall’s natural leaf drop.
Cover the beds with leaves to enrich the soil as they decompose. Leaf litter provides overwintering shelter for pollinators and other garden inhabitants.
Leave the Leaves
Leaves have much to offer in the way of fall beneficial insect habitats. There’s rich biodiversity beneath the leaves, which provides refuge until spring’s reemergence. In addition to a natural mulch, leaves provide ecological benefits for bugs that nest, lay eggs, and overwinter among them.
There are several ways to make use of fall’s natural leaf drop. Let them lie in place to decompose over the season. Or, rake whole leaves into garden beds and around trees as mulch to provide insulation and soil enrichment as the leaves break down. Entire leaves are best for habitat for overwintering insects and more.
Wait until spring’s temperatures reach the mid-50s (~13°C) to thin leafy layers or make use of leaf piles. This gives emerging pollinators and other insects time to leave the shelter in warm weather.
Don’t Cut Back Certain Perennials
Some herbaceous perennials, like echinacea, coreopsis, Joe Pye weed, and rudbeckia, have hollow stems and dried leaves that become nesting cavities for native bees and other insects. Ornamental grasses are a haven for birds and small mammals for food and shelter.
There’s a balance between cutting back herbaceous perennials to prevent fungal disease and leaving woody specimens standing. Go ahead and cut back perennials like tall garden phlox, monarda, yarrow, and hostas. Do a final deadheading sweep for any you don’t want to self-seed.
Consider leaving those with added benefits, even if not as tidy as we’re accustomed. The plants bring life to the resting garden, even in dormancy.
Create a Refuge
Since many of our garden inhabitants remain nearby all year, protective spaces like pollinator hotels and bug snugs are fun ways to offer shelter for a diversity of insects. With cozy coverage tailored to support specific bugs, we support a continued population throughout the seasons. The insects use the “hotel rooms” as a refuge for nesting and as incubators for eggs and larvae.
Pollinator hotels and bug snugs incorporate economical materials like those we have around the house and ones found in nature. And, they make creative projects for kids, who can help build the spaces and watch the insect activity.
Pollinator Hotel
Pollinator hotels serve as shelter spots for all-important garden insects like non-aggressive solitary bees and wasps. The spaces offer easy shelter for cavity-nesting insects. Bugs that may visit include leafcutter bees, carpenter bees, mason bees and wasps, and potter wasps.
The shelters offer a roof cover over tubes and tunnels that become the nesting sites. Hollow reeds and bamboo are useful materials to arrange in a bundle, and each has the potential to become a home for native pollinators. Other methods include drilling holes of varying diameters and lengths into logs and small, thick pieces of wood. Stacked grooved boards are an additional resource.
Opt for one type of setup, or mix and match tubes, drilled logs, and grooved wood to attract a variety of bees. Each has different preferences in the type of nest and in the diameter of the opening. They’ll supplement the “rooms” by filling them with natural materials.
Bug Snug
A “bug snug” is a cozy spot made of stacked twigs, leaves, and evergreen boughs that create burrows for insects and other garden life. Simple structures like tripod branches filled with natural materials create attractive overwintering sites. The snugs offer warmth and insulation against the elements, protection against predators, and are easy to make with landscape materials.
Brush Piles, Rocks, and Logs
Snags, brush piles, stones, and logs provide natural habitat options for fall beneficial insects. If you have a naturalized area of the garden, let debris remain in place or in piles and stacks. Situate these habitat options out of the neighbor’s sightline, if necessary. Screen them with plantings or place them in out-of-sight corners or the yard.
