This article was first published in the July–August 2020 issue of MOSES Organic Broadcaster
Insects are an essential link in Earth’s ecology. While a small number of pest insects tend to capture most of a farmer’s attention, the overwhelming majority of insects are not only beneficial, but also critical to our survival. For example, insect pollinators are essential to the production of more than two-thirds of the world’s crop species and contribute $20 billion annually to US agriculture. Similarly, despite chemical-based pest management, beneficial (predatory and parasitoid) insects provide at least $4.5 billion in free pest management to US farms annually. Beyond agricultural economics, pollinators play a critical role in maintaining the diversity and function of our natural ecosystems.
Despite these (and numerous other) contributions, many insects are in serious decline. Habitat loss and degradation, as well as pesticide use and climate change, are driving the loss of insects to the point that one-quarter of North American bumble bee species are currently facing extinction and even some of our most common species, such as the monarch butterfly, have experienced declines of roughly 80% over the past 20 years.
At a field day at Scattergood Farm in Iowa, Sarah Foltz Jordan, center, explains the process of native habitat installation when starting from seed. (Photo: Liz Kolbe, Practical Farmers of Iowa.)
To help reverse these declines, the Xerces Society has been working with farmers across Iowa to create a network of on-farm demonstration sites that showcase a wide variety of pollinator habitat options and installation methods. This project, supported by a Conservation Innovation Grant from the Iowa Natural Resources Conservation Service (NRCS), seeks to not only boost local insect populations on each individual farm, but also to design projects and test ideas that other farmers in the community and across the Midwest can learn from. Many of the participating farms are serving as sites for field days and workshops, where, already, hundreds of farmers and community members have had the opportunity to learn about habitat establishment methods, maintenance, organic weed control, plant identification, pesticide drift protection, edible/saleable native plants, and more.
Happily, “pollinator habitat” often does much more than support insects. Our farmer partners consistently emphasize the value of insect habitat in addressing other common concerns on the farm, such as soil health, nutrient management, water quality, farm aesthetics, farmer quality of life, and wildlife conservation more broadly.
When it comes to habitat on farms, there truly is something for everyone, ranging from relatively simple annual flowering cover crops and cut-flower gardens, to more complicated orchard understory plantings and native prairie restorations. A few of the habitat options we’ve been focusing on with our Iowa farm partners are highlighted below.
Beetle banks are long, linear strips of native plants integrated into crop fields to provide shelter for predatory ground beetles and other insects. These creatures, in turn, help support natural pest control and pollination on farms. Historically more common in Great Britain, this practice has recently been gaining momentum in the U.S. Upper Midwest.
Beetle banks are especially well suited for organic farms since these cropping systems are often highly reliant on beneficial insects for pest control, yet also often utilize regular cultivation for weed control. Establishing strips of habitat directly within or adjacent to crop fields offers ground-dwelling predators a critical refuge from soil disturbance, and promotes the movement of pollinators and predators into crop fields where their pollination and pest control services are most needed.
Ground beetles (Carabidae) are fearsome hunters and will kill prey much larger than themselves, illustrated by this Agonum species beetle attacking a caterpillar. Largely nocturnal, ground beetles are not often seen, but offer important pest control services on organic farms. Dr. Kirk Larsen of Luther College recently launched a monitoring project at four Iowa farms where the Xerces Society has installed beetle banks, finding over 1,400 individual ground beetles, representing 43 different species, with an average of 26 different species per farm. (Photo: Jenn Forman Orth, Flickr [CC 2.0].)
Beetle banks are typically composed primarily of native bunch grasses (such as little bluestem, side-oats grama, and prairie Junegrass) but may also include a wildflower component. For our Iowa farms, we included wildflowers in all of our strips at a rate of about 40% wildflowers, 60% grass. Of course, this ratio could change depending on what insects you are trying to support and the resources you have on your farm. For example, if your farm has limited nectar and pollen supplies, you may wish to have a stronger wildflower component but still include grasses for structure, nesting habitat, and to help the planting resist invasion from grassy weeds.
When selecting plants, it is helpful to familiarize yourself with the natural plants in your area and use this knowledge, along with soil conditions at your site, to guide your plant selection. For the flowering component, try to include representatives from as many different plant families and genera as possible in order to support a wider range of insects, including bees and butterflies that may be specialized to feed only on certain plants. Check the bloom time of the species in your selection to make sure you have at least a few species blooming in early spring, late spring, and onward throughout the growing season.
Strip length and width will vary depending on the cropping system, space available, and other factors. On vegetable farms, we have been planting strips as narrow as 4 to 8 feet; on grain farms, as wide as 25 feet or more. Several farmers have expressed a preference for placing strips on the edge of a crop field rather than the interior so that one edge can be mowed to manage weeds while the other edge is up against crops.
Although large native habitat plantings are best established from seed, smaller plantings can be established using plugs (small plants). The plug approach requires less weed control in advance of the planting (since the plants will have a better competitive advantage over the weeds) and in the early years of establishment (spot-weeding rather than regular mowing). In addition, plug plantings establish far more quickly than seed plantings, often flowering in the first growing season or certainly by the second. The downside of starting with plugs is, of course, higher cost. However, most vegetable growers are well equipped to grow plant starts; they can grow out at least some native plant species fairly easily and purchase harder-to-grow plugs from a local native plant nursery.
Here is just a short list of a few wildflowers, grasses, and sedges that are native to much of the Midwest and relatively easy to grow out for use as transplants:
Achillea millefolium (yarrow)*
Agastache spp. (hyssop)
Asclepias incarnata (swamp milkweed)
Aster spp. (New England aster and others)
Astragalus canadensis (Canada milkvetch)
Coreopsis spp. (coreopsis)
Dalea spp. (prairie clover)*
Desmodium canadense (Canada tick trefoil)*
Echinacea pallida (echinacea)*
Eupatorium spp. (boneset)
Eutrochium spp. (Joe Pye weed)
Eryngium yuccifolium (rattlesnake master)
Helianthus spp. (native sunflowers)
Helenium autumnale (sneezeweed)*
Heliopsis helianthoides (early sunflower)
Monarda spp. (bee balm, spotted bee balm)*
Pycnanthemum spp. (mountain mint)*
Solidago speciosa (showy goldenrod and others)
Silphium spp. (compass plant, cup plant, etc.)
Tradescantia spp. (spiderwort)
Verbena spp. (vervain)
Vernonia spp. (ironweed)
Zizia aurea (golden Alexanders)
GRASSES AND SEDGES
Andropogon gerardii (big bluestem)*
Bouteloua curtipendula (side-oats grama)*
Bouteloua hirsuta (hairy grama)*
Bromus kalmii (prairie brome)*
Carex brevior (plains oval sedge)
Carex vulpinoidea (fox sedge)
Elymus spp. (wild rye and bottlebrush grass)*
Koeleria macrantha (prairie Junegrass)*
Panicum virgatum (switch grass)*
Schizachyrium scoparium (little bluestem)*
Sorghastrum nutans (Indian grass) *
Sporobolus spp. (prairie dropseed and others)
[*Seed does not require any treatment (e.g., cold moist stratification) to break dormancy.]
If you are new to growing native plugs, it’s worth noting that native plant starts tend to grow much more slowly and irregularly compared to vegetable starts. For example, germination may be staggered over several weeks, and it can take many months to get from a seed to a plant that is ready to be transplanted. However, this longer growing time typically isn’t a problem, since native plugs can be out-planted at any time during the growing season, as long as they are watered at the time of planting and receive additional watering as needed. On that note, some farmers prefer to place drip irrigation on their strip plantings during the first growing season as the plants are getting established.
As far as plant spacing, we typically plant plugs on one-foot centers, and try to design the planting to have smaller-stature species clustered together in patches so they do not get outcompeted by taller species. For example, if you were planting a 100-foot linear strip planting that is five feet (and five rows) wide, you could start by dividing your larger and smaller plants into two groups and then plant 10 linear feet (50 plants) of taller plants followed by 10 linear feet of shorter plants, and so on, throughout the planting for a “wavelike” effect when the plants reach maturity.
At Grow: Johnson County Farm in Iowa City, the beetle banks were designed to match the standard bed width used on the farm in order to utilize equipment regularly used for vegetable production. A tractor-mounted water-wheel transplanter was used to streamline the process of transplanting. Weed control during the first growing season was also streamlined at this farm, using tractor-mounted finger weeders designed for in-row cultivation. After the first growing season, native plants are typically filled in enough to not require anything more than occasional spot-weeding by hand.
Site preparation is one of the most important and inadequately addressed components for successfully installing pollinator habitat. Pre-planting weed control is especially critical when starting from seed, but also can be important when starting from plugs, depending on the weed pressure. As all farmers know, not all weeds are created equal, and some can be particularly trying. In the Midwest, we typically plan on at least one growing season of organic weed control prior to planting native perennial habitat—an up-front investment that really pays off in the long-term success of the planting. The Xerces conservation guide, Organic Site Preparation for Wildflower Establishment, outlines a variety of organic methods for weed control, including pros and cons of each method, step-by-step instructions, and regional timelines and checklists for preparing both small and large sites.
The Xerces Society team plants buckwheat to smother weeds prior to planting insect habitat. This planting from 2019 set seed (unintentional) and came back as a very dense ground cover shortly after the plugs had been planted. In the 2020 growing season, the buckwheat seed set from the previous season was not problematic; in fact, it served as a “nurse crop” to hold other more challenging weeds at bay while the native plugs were getting established. (Photo: Xerces Society / Sarah Foltz Jordan.)
Lately, our go-to methods for site prep are smother cropping (growing a densely planted cover crop—typically buckwheat—to smother out existing vegetation), and solarization (smothering existing vegetation with clear, UV-stable 6-mil high-tunnel plastic). At River Root Farm in Decorah, we had great luck using a new (to us) approach of stale seed bedding (using irrigation and silage tarps to encourage the germination and subsequent death of weed seeds). On another farm (Nature Haven Farm in Garnavillo), we are continuing to explore the use of pigs for rooting up difficult weeds prior to planting.
Native Flowering Hedgerows
Native flowering shrub hedgerows are another favorite habitat option on farms. We typically recommend hedgerows when spring bloom is limited on the far, edible/saleable products are desired, and/or weed pressure is such that it would be very difficult to get smaller wildflower plants established. Native shrubs not only support wildlife with abundant food (nectar, pollen, foliage, fruits), but also provide nesting and overwintering shelter in their branches, stems, older trunks, and undisturbed soil at the ground level. Hedgerows also can be used to provide visual screening from roads or adjacent fields, reduce wind and dust, capture snow, intercept pollution, and more. These living fences simultaneously beautify farms and provide supplies to make a variety of products, such as jams, juices, syrups, tinctures, teas, wicker for basket weaving, branches for floral arrangements, and other products.
The following list highlights a few of the many native flowering shrubs with high value to pollinators. Almost all of these plants have fruit or other parts that can also be eaten by humans and offer a great opportunity for us to diversify our own diets.
NATIVE FLOWERING SHRUBS:
Amelanchier spp. (Juneberry)
Amorpha spp. (leadplant and false indigo)
Aronia melanocarpa (aronia)
Ceanothus americanus (New Jersey tea)
Cornus spp. (dogwood)
Crataegus crus-galli (cockspur hawthorn)
Prunus americana (wild plum)
Ribes spp. (currants)
Rosa spp. (roses)
Rubus spp. (raspberries and blackberries)
Salix spp. (willow)
Sambucus spp. (elderberry)
Spiraea spp. (meadowsweet)
Vibernum lentago (nannyberry)
Vibernum opulus var. americanum (highbush cranberry)
As always, be sure to choose plants that match your soil moisture levels and other site conditions. For more information on native hedgerows and the process for getting them established, see our article in the May|June 2016 issue of the Organic Broadcaster.
A mature hedgerow planted with native shrubs that provide food for pollinators and other insects, but also people—the plants all produce edible fruit. Although not created as part of the project described in this article, this hedgerow was planted on a farm in Minnesota under the guidance of Xerces staff. (Photo: Xerces Society / Sarah Foltz Jordan.)
We are currently seeking farmers in western Wisconsin (especially the Northwest and Driftless regions) who may be interested in creating or enhancing habitat on their farms. For more details, email [email protected].
Additionally, the USDA’s Natural Resource Conservation Service offers two programs, the Environmental Quality Incentives Program (EQIP) and the Conservation Stewardship Program (CSP), that could help fund your habitat projects. Contact your local NRCS field office to ask about opportunities.
The Iowa farmers who participated in this project include: Helgeson Farms in Lake Mills, Grinnell Heritage Farm in Grinnell, Genuine Faux Farm in Tripoli, Blue Gate Farm in Chariton, Mustard Seed Community Farm in Ames, Mugge Family Farm in Sutherland, Smart Farm in St. Charles, Scattergood Farm and School in West Branch, Grow: Johnson County Farm in Iowa City, Partridge Family Farm in Wall Lake, River Root Farm in Decorah, Rose Farm in Norwalk, and Nature Haven Farm in Garnavillo.
Download our in-depth conservation guidelines on Habitat Planning for Beneficial Insects
Read more about Organic Site Preparation for Wildflower Establishment
Get an overview of pollinator conservation on farms, Farming for Pollinators
Read more about our work to protect pollinators