"Flowers for borders" is the concept behind ground-breaking research and has revealed how gardeners can attract beneficial insects — ladybugs, lacewings, ground beetles and other insects that feed on pests — simply by planting certain flowers. We've been monitoring this research and compiling a list of plants that are both highly ornamental and proven effective in attracting and sheltering beneficials. Here's our exclusive special report on these beautiful and valuable plants.
To get energy to search for their prey, or to reproduce, many beneficial insects feed on nectar (for carbohydrates) and pollen (for protein) from flowering plants. Researchers are discovering that some flowers are much better sources of nectar and pollen to sustain beneficial insects than others. Studies are also revealing the best plants to grow for shelter to help good bugs thrive. And as an added bonus, many of the nectar sipping/pest-eating insects that are attracted to flower pollen will also pollinate your fruit and vegetable crops and increase your yields.
Here are the top ten ornamental plants we recommend for Beneficial Borders. All are very easy to grow and ideal choices even for new gardeners.
The 11 Best Plants for Beneficial Borders
1. Bachelor's Buttons or Cornflower (Centaurea cyanus) This beautiful blue wildflower has extrafloral nectaries, which means the plant's leaves release nectar even when the flowers are not blooming. Research in Germany has found that bachelor button nectar has a very high sugar content of 75 percent. This nectar is highly attractive to flower flies, ladybugs, lacewings, and beneficial wasps. Sow easy-to-grow bachelor's buttons seeds directly in the garden in fall or early spring; plants usually reseed energetically.
Photo: (cc) Carl Lewis/Flickr
2. Sweet Alyssum (Lobularia maritima) This low-growing annual makes a lovely white, highly fragrant edging for flower beds, or a fast-growing, beneficial-attracting, weed-smothering ground-cover to interplant in vegetable beds. Numerous studies have confirmed that sweet alyssum is highly attractive to aphid-eating flower flies. You can start with seeds, or buy bedding plants for earlier flowering.
Photo: (cc) Carl Lewis/Flickr
3. Borage (Borago officinalis) This annual herb has bright blue clusters of edible, cucumber-flavored flowers. Studies in Switzerland have shown borage to be exceptionally attractive to good bugs, with an average of over 100 beneficials found in just 1 square yard of borage. In addition, common green lacewings have a very strong preference to lay their eggs on borage. Look for borage on garden center seed racks and mail order seed catalogs.
4. Cup Plant (Silphium perfoliatum) This 6 to 8 foot tall native perennial has a unique feature that makes it a star in Beneficial Borders. The leaves wrap all the way around the stems, forming a deep cup that collects dew and rainwater. Beneficial insects and small birds can easily use the leaves as landing pads, and then drink from the cups. Cup plant is an outstanding ornamental, with large attractive leaves and clusters of yellow flowers in mid to late summer that are highly attractive to many insects. It's hardy to zone 4 or 3. To start seeds, sow in fall, or store in damp sand in the refrigerator for 6 to 8 weeks before planting in spring.
5. Anise Hyssop (Agastache foeniculum or A. rugosa, aka Korean mint) Perennial, summer-blooming anise hyssop has fuzzy purple or violet flower spikes on 2 to 3 foot high plants with licorice-scented leaves. The nectar-rich flowers are very attractive to both butterflies and pest-eating beneficial insects. Anise hyssop is hardy in zones 6-9; Korean mint in zones 5-8.
Photo: (cc) Anna/Flickr
6. Golden Marguerite (Anthemis tinctoria) This long-blooming perennial produces bright yellow 2 inch daisies that are highly attractive to five key kinds of beneficials—ladybugs, lacewings, flower flies, tachinid flies and mini-wasps. It was the only plant out of 170 species to score this well in a 3-year study at botanical gardens in Colorado and Wyoming. Golden marguerite thrives in poor soils, growing 2 to 3 feet high and wide. Deadhead (remove spent flowers) to promote rebloom, and divide plants every 2 to 3 years. Hardy in zones 3 to 7.
Photo: (cc) Sabrina Huber/Flickr
7. Fennel (Foeniculum vulgare) Long-lasting fennel flowers are extremely attractive to all nectar-feeding beneficial insects, and the feathery green or purple foliage looks wonderful in spring and early summer. Fennel is a host plant for the caterpillars of the anise swallowtail butterfly. The seeds and leaves are also eaten by humans, and are excellent in salads (leaves) or spaghetti sauce (seeds). The plants grow about 5 feet high and are perennial in zones 6-9.
Photo: (cc) Weisserstier/Flickr
8. Mountain Mints (Pycnanthemum virginianum and P. muticum) Both of these native mountain mints (and many other members of the mint family) are excellent choices for Beneficial Borders. Short-toothed mountain mint (P. muticum) has broad clusters of small white flowers surrounded by unique, showy white bracts; it makes beautiful dried flowers. Mountain mints grow 2 to 3 feet tall and are hardy from zones 4 to 7. Not yet widely available, these plants can be ordered from Sunnybrook Farms, 440-729- 7232.
9. Pussy Willows (Salix species) Willows are especially valuable because they produce pollen so early in the spring, when many beneficials are just emerging. Pussy willows are super-easy to grow and fun to cut for flower arrangements. Most garden centers will carry pussy willows in spring, or you can root cuttings from a neighbors' shrub in water.
Photo: (cc) Dag Endresen/Flickr
10. Ornamental Grasses All clump-forming grasses provide excellent summer shelter and overwintering sites for ground beetles, ladybugs and other beneficials. Studies in England found more than 1,500 predators per square yard in grass-covered "beetle banks" planted in arable fields.
11. Corn Corn tassels produce large amounts of pollen that is a nutritious protein source for many beneficials. And while we usually don't think of corn as an ornamental, it's actually very striking when planted in flower beds. Think of it as a very fast- growing, tall ornamental grass. And if you want an extra bit of beauty, try the 'Japonica' corn which has green, white and pink variegated leaves.
Photo: (cc) Matt Lavin/Flickr
Plants for Pollen and Nectar
Basils (Ocimum basilicum)
Bachelor's buttons (Centaurea cyanus)
Bee phacelia (Phacelia tanacetifolia)
Birds Eyes (Gilia tricolor)
Blue Lace Flower (Trachymene coerulea, aka Didiscus coeruleas)
Borage (Borago officinalis)
California poppy (Eschscholtzia californica)
Candytuft (Iberis umbellata)
Chervil (Anthriscus cerefolium)
Coriander (Coriandrum sativum)
Corn (Zea mays)
Corn poppy (Papaver rhoeas)
Cosmos (Cosmos bipinnatus)
Dill (Anethum graveolens)
Lobelia (Lobelia erinus)
Meadow foam (Limnanthes douglasii)
Mexican sunflower (Tithonia rotundifolia)
Pincushion flower, aka Sweet scabious (Scabiosa atropurpurea)
Signet ('Gem') marigolds (Tagetes tenuifolia)
Sunflowers (Helianthus annuus)
Sweet alyssum (Lobularia maritima)
Sweet marjoram (Origanum majorana)
Tidy Tips (Layia platyglossa)
Early research on flowers for beneficials has focused primarily on weeds and wildflowers growing around farms, to discover which of these plants farmers might encourage to help with pest control. Gradually, more ornamental plants are being identified, and we now have a very nice list you can choose from:
Asters (Aster alpinus and A. tartaricus )
Angelicas (Angelica )
Anise hyssop (Anastache foeniculum)
Basket of Gold (Aurinia saxatilis)
White lace flower, aka Bishop's weed (Ammi majus)
Blue cardinal flower (Lobelia syphilitica)
Bog rosemary (Andromeda polifolia)
Carpet bugleweeds (Ajuga)
Coral vine (Antigonon leptopus)
Crimson thyme (Thymus serpyllum 'Coccineus')
Crocus (Crocus )
Cup plant (Silphium perfoliatum)
Evening primrose (Oenothera biennis)
Fennel (Foeniculum vulgare)
Feverfew (Chrysanthemum parthenium)
Garlic Chives (Allium tuberosum)
Golden marguerite (Anthemis tinctoria)
Jerusalem artichoke (Helianthus tuberosus)
Korean mint (Anastache rugosa)
Lavender globe lily (Allium tanguticum)
Lovage (Levisticum officinale)
Mountain Mints (Pycnanthemum muticum and P. virginianum)
Mountain sandwort (Arenaria montana)
Pincushion flower (Scabiosa caucasica)
Poppy mallow (Callirhoe involucrata)
Queen Anne's lace (Daucus carota)
Rocky Mountain penstemon (Penstemon strictus)
Sea lavender (Limonium latifolium)
Sea pink (Armeria alliacea)
Stonecrops (Sedum kamtschaticum, S. spurim, S. album)
Fernleaf Tansy (Tanacetum vulgare var. crispum)
Teasel (Dipsacus) Thrift (Armeria maritima)
Green lace flower, aka Toothpick ammi (Ammi visnaga)
Wild Bergamot (Monarda fistulosa)
Wood Betony (Stachys officinalis)
Trees and Shrubs
Top choices include willows (for their early spring pollen to provide a food source and get overwintered beneficials off to a strong start), forsythia, firethorn, potentilla, ceanothus, four-winged saltbush (Atriplex canescens), euonymous, and Texas sage (Leucophyllum frutescens).
Clovers and other soil-building cover crops provide pollen and nectar, alternate insect prey, and shelter. Crimson clover is as beautiful as any "regular" flower, and buckwheat is a standout because it grows very, very fast and has extrafloral nectaries that attract a wide variety of beneficials even before it begins blooming.
Plants that Shelter Beneficials
Blue wildrye (Elymus glaucus)
Deer grass (Muhlenbergia rigens)
Orchard grass (Dactylis glomerata)
Tufted hairgrass (Deschampsia caespitosa)
Velvet grass (Holcus lanatus)
Permanent plantings of perennials, trees and shrubs.
Especially good are dense low-growing groundcovers, perennial cover crops, and certain perennial flowers with woody stems and/or dense crowns, such as yarrows, comfrey, and coneflowers. Comfrey provides highly attractive hibernation sites for spiders, with up to 240 spiders per square yard, compared to only 10 spiders per square yard in adjoining wheat fields.
These plant lists were compiled from a variety of scientific sources, including Enhancing Biological Control—Habitat Management to Promote Natural Enemies of Agricultural Pests, edited by Charles H. Pickett and Robert L. Bugg, and a 3-year study of 170 species of ornamental plants by Mohammed Al-Doghairi and Whitney Cranshaw, Ph.D. of Colorado State University.