Grow native plants that attract predatory insects, trap crops, and manage generalist plant predators and living mulch to provide resources for beneficial insects.
Farmscaping is the management of the entire farm ecosystem to favor beneficial insects, using every available piece of ground. Though many eco-friendly plantings focus on pollinators, farmscaping is about insect predators.
Successfully attracting beneficial insects that feed on pests requires knowing your predators. Beneficial insects include fireflies, ground beetles, lacewings, ladybugs, mantids, soldier beetles, and wasps, as well as robber, syrphid, and tachinid flies. They’ll be able to control some common garden pests, including aphids, the Colorado potato beetle, the striped cucumber beetle, caterpillars, grasshoppers, mites, snails, slugs, thrips, and whiteflies. Perhaps contradictory to the way we generally think of pest control, both prey and predator must be present for farmscaping to work; after all, your predators need something to eat! The key is to encourage more beneficials than pests.
Sometimes, both the adult and larval stages of a predator will feed on pests, as with ground beetles and mantids. However, some beneficials are only predatory at the immature larval stage, as with many flies and wasps; for these cases, offer nectar and pollen to attract the adults and get their larvae. Furthermore, insects will need overwintering locations and access to nesting materials. So, to maintain a population of beneficial predatory insects for a good duration of your growing season, offer food and housing for all.
Native Plants That Attract Predatory Insects
Include a diversity of plants in your farmscaping, as each plant has something different to offer. Those that bloom early, such as crimson or Italian clover (Trifolium incarnatum) and wild lilac (Ceanothus spp.), or late in the season, such as goldenrod (Solidago spp.) and sunflower (Helianthus spp.), will help extend beneficials’ active periods. Those that can withstand weather extremes, such as drought and high temperatures, will provide a consistent source of food throughout the summer. Examples include coreopsis (Coreopsis spp.), cup plant (Silphium perfoliatum), West Coast native globe gilia (Gilia capitata), cowpea (Vigna unguiculata), and partridge pea (Chamaecrista fasciculata).
Plants with “extrafloral nectaries,” or nectaries located outside plants’ flowering structures, are especially attractive to the nectar-gathering adults of many beneficial predatory insects. Plants with extrafloral nectaries include cornflower (Centaurea cyanus), elderberry (Sambucus spp.), sunflower, cowpea, and partridge pea. Also attractive to adult beneficial insects are the umbel-shaped flower heads of the Apiaceae family, including angelica (Angelica spp.), dill (Anethum graveolens), fennel (Foeniculum vulgare), lovage (Levisticum officinale), and eryngo (Eryngium spp.). Their many small, shallow flowers offer a great deal of nectar to beneficials of all sizes, including the miniscule ones that can’t access the nectar of larger flowers. Shallow nectaries are also a trait of mountain mint (Pycnanthemum spp.).
Perennial Plants for Nesting Materials
Perennial features are an asset with farmscaping, given their emphasis on nesting and overwintering spaces, such as hollow stems, pithy branches, and undisturbed ground, both bare and with a surface buildup of leaves and other plant materials. Plantings with perennials will offer necessary nesting materials, such as peeling bark and coarse plant fibers.
- Beetle berm or bank. This is often slightly hilled and chiefly populated with un-mown native grasses, whose fibrous root systems make the soil beetle-friendly. A beetle berm supports ground beetles by offering both hunting grounds and an excellent overwintering habitat. Ravenous generalist predators in both the larval and adult stages, different ground beetles are known to alter their diets during the season based on prey availability, and they’ll even eat weed seeds. This flexibility is an asset when trying to keep beneficial insect populations high. Big bluestem (Andropogon gerardii), Indian grass (Sorghastrum nutans), and switchgrass (Panicum virgatum) are good options for the berm.
- Filter strip. Plant a filter strip to reduce the flow of sediment, organics, nutrients, and other contaminants from runoff into waterways. Filter strips can be for aesthetics, which can include bee balm (Monarda fistulosa), black-eyed Susan (Rudbeckia spp.), and wingstem (Verbesina alternifolia), or for managed animal grazing with sainfoin (Onobrychis viciifolia), purple prairie clover (Dalea purpurea), and alfalfa (Medicago sativa).
- Ground cover. This offers erosion control along slopes and on sandy and rocky soils. Use ling heather (Calluna vulgaris), lemon thyme (Thymus x citriodorus), berseem clover (Trifolium alexandrinum), and New Zealand white clover (T. repens).
- Living mulch. This provides weed control and soil protection in gardens and in perennial fruit plantings, such as orchards. My favorite living mulches are clovers – crimson, red (Trifolium pratense), subterranean (T. subterraneum), and white.
- Permanent and perennial insectary strips. These are chiefly composed of native grasses and wildflowers, including spiderwort (Tradescantia spp.), self-heal (Prunella vulgaris), wild field mint (Mentha arvensis), and rattlesnake master (Eryngium yuccifolium). Their placement sets them apart from the other ground uses.
- Permanent border. These may be composed of various trees or shrubby and herbaceous vegetation. Borders can be a good place for rock piles, brush piles, wooden posts, tree stumps, and dead-but-not-dangerous trees, each bringing a unique aspect to the ecosystem. Border plants range from basswood (Tilia americana) and wild cherries (Prunus serotina), to goldenrod and milkweed (Asclepias spp.) and everything in between.
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- Windbreak and hedgerow. Whereas “windbreak” is often used to describe a less-diverse, though still potentially valuable, planting for protection from the sun and wind, “hedgerows” have an emphasis on densely constructed habitats for beneficial insects and wildlife and microclimates for plants. Plant trees, shrubs, and perennial forbs and grasses there. These can include hypericums (Hypericum spp.), blackthorn (Prunus spinosa), elderberry, the spring-flowering meadowsweet (Spiraea spp.), and wild lilac.
Annual Plants for Pollen and Nectar
Though permanent plantings are valuable, annual ones can be used to great advantage, especially when it comes to providing continuous supplies of pollen and nectar.
Annual or temporary insectary strips. These consist of familiar annuals that are easily sourced, affordable, and (as a diverse mixture) support all manner of beneficial insects. They commonly contain coriander, dill, basil (Ocimum spp.), cosmos (Cosmos bipinnatus), and dwarf sunflowers, to name a few.
- Companion plantings. These can serve many purposes for cash crops, from attracting pollinators, as dill will; to disguising them from pests with a strong scent, which marigolds (Tagetes tenuifolia) are famous for doing; to camouflaging crops from would-be egg-laying pests with “inappropriate landing confusion,” causing the pests to leave the area and seek appropriate host plants elsewhere (a great job for red clover) – and all this while also feeding the “predatory” nectar and pollen gatherers!
- Cover crops. These protect the ground through winter and resume growth in spring. Chicory (Cichorium intybus), crimson clover, hairy vetch (Vicia villosa), and radish (Raphanus sativus) will also offer desirable spring flowers. Furthermore, planting cover crops involves removing cash-crop residue, which is often a source of pest-overwintering sites.
- Green manures. Use these for the summer season instead of cash crops to add nutrients to the soil; consider quick-growing buckwheat (Fagopyrum esculentum), lacy phacelia (Phacelia tanacetifolia), cowpea, partridge pea, and the lanky white sweetclover (Melilotus albus).
- Strip intercropping or multiple cropping. This is a great way to incorporate insectary, living mulch, and companion plants into larger-scale fields by alternating cash and beneficial crops. Strip planting into an established cover crop or into green manure would further enhance benefits by including strips of undisturbed soil.
- Trap crops. These are a specific kind of companion planting. Trap crops are gathering places for pests that are intended to divert their attention from cash crops. However, situations should be evaluated case by case: For example, few gardeners will allow squash vine borer adults to remain as potential food. Trap crops can be of the same plant family as the cash crop, as with trap collards or radishes in cabbage or broccoli, and blue hubbard winter squash with any cucurbit cash crop. Trap crops can also be of a different family; alfalfa, common vetch (Vicia sativa), and sweet alyssum (Lobularia maritima) are used as trap crops for many cash crops, from strawberries to potatoes.
Trap Crops or Insectary Plantings
Now that we know the “what” of farmscaping, let’s take a look at the “where.” Pests will often overwinter either in crop debris or in the undisturbed perimeters of plots, and then they’ll move in. To prevent this, plant trap crops or insectary plantings between perimeters of your land and the cash crops. Bring beneficials close to their food with insectary plantings among the interiors of gardens.
Larval predators of any kind don’t naturally travel far, nor do adult ground beetles; if you want them present, plant their habitats nearby. For insects that hunt and bring prey to their larvae, such as wasps, the closer their nests or larvae are to the “hunting grounds,” the less time they’ll spend traveling. Having food for the adult wasps close to the crops you want them to patrol will increase their effectiveness as well.
Establishing perennial plantings in a perennial cropping system is easily done; establishing perennials in an annual system requires more planning. It’s worth the effort, as “perennial islands” within an annual cropping system will increase the area impacted by beneficials. Additionally, establishing “corridors” of a mixture of annuals that lead from perennial perimeters to the center of annual cropping systems will help move in predators.
Managing Living Mulch
Farmscaping isn’t just about the flowers you plant, but also the way you manage them. For example, leaving spent stems and leaves to cover the ground in perennial flower or insectary areas helps create the dark, damp, and cool sheltered areas favored by predatory arthropods, such as ground beetles, wolf spiders, and centipedes.
Ground cover and living mulches, particularly in perennial areas that allow matter to build up, provide additional shelter, especially for overwintering; alfalfa, mints, sweet alyssum, and perennial American vetch (V. americana) are distinctly effective at this. Mulch, such as grass clippings, compost, and other organic materials, can be used in both perennial and annual settings to achieve the same effect; plus, decaying plant matter will attract organisms that feed on it, creating additional prey.
Plants that tolerate mowing, such as clovers, can be cut after flowering and before seed set to stimulate further flower sets. Those plants with a branching habit, such as cosmos, rudbeckia, and sunflowers, can be deadheaded to trigger additional blooms from axillary shoots. While perennial areas benefit from selecting flowers for successional blooming, successional planting is an additional way to keep annual areas flowering.
In both annual and perennial plantings, mass planting or species “clumping” frequently adds to the attractiveness of flowers, as opposed to the same plants sparsely scattered in a mix with others. This is particularly seen with figwort (Scrophularia spp.), spiderwort, and basils. My favorite for mass planting is tulsi, or “holy basil” (O. tenuiflorum). Where possible, minimum-4-foot-square patches are a good planting pattern for most plants.
Managing Generalist Plant Predators
Balance is key to farmscaping. For example, ground beetles are incredible beneficials, being generalist predators in both the larval and adult stages. However, they’re such generalists that they’ve been known to eat other beneficials. Furthermore, clover, while attractive to many desirable insects, can also attract lygus bugs. To keep this pest in check and to stay in clover, you’ll need a variety of plants to attract a range of beneficials, some of which will feed on the lygus bugs.
Having various beneficials will improve your system in other ways. Some predators feed on adult pests, while others consume immature pests and eggs, together increasing the likelihood of predation.
And the many aerial predators, as well ascatching prey themselves, can cause some pests to flee downward where terrestrial hunters, such as those voracious ground beetles, may catch them – if they’re present!
By using land in different ways and creating “bloom time” for as much of the year as possible, a diversity of plants will improve your chances of attracting and supporting a thriving population of beneficial insects to help with your pest control. So, do what you can to hang out the welcome sign!
Insect-Eating Birds and Bats
Birds and bats also have a place in farmscaping. Spring, when they’re raising their young, is the most active insect-catching period for both. Both can be encouraged to remain on your property with freestanding nesting boxes and “customized” portions of buildings.
Insect-eating birds range from wrens and chickadees to bluebirds and barn swallows. Barn swallows will build their own nests along the eaves of barns, while the others will require boxes with opening holes of the appropriate size (up to 1-1/4 inch round for chickadees and wrens, and 1-1/2 inch round or oblong with a 2-inch vertical for bluebirds). These diurnal (daytime) predators will be further encouraged to remain if offered a water source, such as a birdbath, and their preferred plants, which can include cup plant, cosmos, ocean spray (Holodiscus discolor), and sunflowers.
Bat-friendly water sources need to be a bit larger, such as a minimum-10-foot-long pond, since they dive to water for a flyby drink. These nocturnal hunters want warm, dry, and disturbance-free locations during the day, whether in a box or among the beams and rafters of a building.
Leah Smith is a freelance writer and home and market gardener. She works on her family’s farm in mid-Michigan called Nodding Thistle (certified organic 1984 to 2009, principally by Organic Growers of Michigan). A graduate of Michigan State University, she can be reached at NoddingThistle@Gmail.com.
