“I can sit on the porch before my door and see miles of the most beautiful prairie… surpassing, in my mind, the beauties of the sea. Think of seeing a tract of land on a slight incline covered with flowers and rich meadow grass for 20 miles”
John Brooke, an early settler in the Tall Grass Prairies of Texas (1849)
Many beekeepers are interested in putting their bees in locations with diverse forage that produces nectar and pollen across a wide range of the growing season, like a well-stocked pantry that stays full until Winter weather comes around. Unfortunately, such diverse forage has become harder to find. The good news is that researchers are finding that native prairie wildflower plantings in the ‘margins’ of agriculture can be beneficial not only to pollinators but also to the bottom line of commercial growers.
How Prairies Came to Be
At one time trees dominated the landscape of the continental United States from coast to coast1. With the upwelling of the Rocky Mountains, a large “rain shadow” was created, robbing the lands immediately east of the Rockies of rainfall. As a consequence, trees retreated to the riverbeds where water was more abundant while short grasses, forbs (flowering plants) and shrubs which required less moisture came to dominate the landscape of what is now called “Short Grass Prairie.”
Further to the east, moisture-laden air rolling northward from the Gulf of Mexico contributed to increased rainfall, enabling taller and more robust prairie plants to grow in “Tall Grass Prairies” of what is now Iowa, Illinois and Indiana. Interestingly, this spectrum of plant height from east to west continues today when one considers the dominant cash crops of the Tall Grass regions (corn) and Short Grass Prairie regions (wheat).
This adaption to rainfall variations took place in soil formed by the repeated advance and retreat of glaciers, massive sheets of ice that dragged and pulverized mineral-laden boulders and rocks from Manitoba and beyond into an extraordinarily rich blend of soil. Eventually, bison converted nutritious prairie grasses into compost; prairie dogs and gophers churned the soil from below, while natural (and, eventually, man-made) fires replenished the soil above with critical nutrients. All of this contributed to one or more inches of new topsoil every one hundred years.
This deep topsoil enabled native prairie plants to grow roots down to twelve feet or more, leaving little doubt that prairie natives could withstand both drought and fire. The prairie biome teemed with life above and below ground. Although dominated in many places by wind-pollinated grasses, native pollinators thrived in the extraordinary diversity of wildflowers that was also part of the North American prairies. This is the landscape that homesteaders found as the American frontier opened in the 19th century.
What Happened to Prairies
Three important factors precipitated a breathtakingly rapid conversion of this prairie ecosystem to cropland between 1840 and 1900. First there was the personal motivation of homesteaders to “pay their way”. They saw this incredibly rich and diverse ecosystem as a landscape filled with nuisances that must be cleared. Second, a new tool – the steel plow invented by John Deere – enabled homesteaders to tear through a tough prairie sod that literally broke conventional machinery. Finally, government policy and officials encouraged the conversion to cropland, exemplified by this statement from a land official in 1868: “. . . the plains are an obstacle to the progress of the nation’s growth . . . in not yielding sustenance for increasing population.”
A steady intensification of agriculture practices and urbanization continues to this day, having trimmed away at prairie remnants so that only 1-2% of residual prairie acreage can be found.
Many beekeepers believe that this loss of naturally flower-rich areas has had a significant impact on the production and health of honey bees. Fortunately, recent research suggests that prairie wildflower restoration not only benefit pollinators but also return a net positive return on investment.
How Restoration Can be Worthwhile
With funding from Syngenta, the Kellogg Foundation and other sources, three research universities studied the costs, benefits and best practices of establishing wildflower-filled field margins on farms. At Michigan State University in 2009, researcher Rufus Isaacs and colleagues seeded fifteen native wildflower species that would provide nectar and pollen across the entire growing season in the margins of five blueberry farms in 2009. They paired each planting with a control field with no wildflower planting and then evaluated crop pollination success by measuring the percentage of fruit set, the berry weight, and the number of mature seeds per berry. They also counted the number of wild pollinator species supported at each of the sites.
Their findings, published in the journal Applied Ecology, showed that were more pollinators in the fields adjacent to the wildflower planting. Importantly, their findings suggest that the wild pollinators complement, not replace, the work of honey bee pollination. They noted an increase in blueberry size and count that was sufficient to fully recover the initial expense of the wildflower planting after only four years.
Encouraged by these findings, Syngenta is now seeding wildflower buffers at commercial farms and at more than sixty golf courses across the country. Isaacs has received funding to expand his research on wildflower plantings at over thirty farms in multiple states and with multiple types of crops.
Meanwhile, at Iowa State University, the Science-based Trials of Rowcrops Integrated with Prairie Strips (called the STRIPS project)4 tested the hypothesis that putting a little bit of prairie in otherwise marginal land could yield significant environmental benefit. They found that re-planting the least productive 10% of farmland with a mix of indigenous prairie plants reduced soil loss by 95%, nutrient loss by 80-90%, water run-off by 44%, and showed a four-fold increase in biodiversity, including pollinators.
In some states there is talk of converting some of the millions of acres of mowed roadsides with low-growing native grasses and wildflowers. The fuel and manpower savings from eliminating the thrice-yearly mowing would go a long ways towards paying for the investment in wildflowers. If replicated widely across the country, such prairie wildflower plantings could have an impact on growers as well as commercial, sideliner and hobby beekeepers.
Like all things worthwhile, developing a landscape of native prairie that is resistant to drought, conserves topsoil, protects water quality and provides support for honey bees and other pollinators takes work. One can purchase live plants, bare root plants, or seeds. Live plants and bare root plants are more expensive but will provide pollinator support sooner. Assuming that we are discussing restoration of a space one quarter-acre or more, it will be most cost-effective to seed the site.
The first step is to select what kinds of plants to seed into the space. Of course, the seed mix should contain wildflowers that are useful to pollinators in general and honey bees specifically. It would be useful to also include some prairie grasses for variety. It would be optimal to select a variety of plants that bloom across the entire growing season. A reputable operation should be able to provide seeds for plants that are appropriate for your location. Identifying your USDA “Plant Hardiness Zone” is only the first step in identifying plants appropriate for your site. One must also consider various characteristics of the site before deciding which plants to seed. For example, clay soil has fine grains, causing it to be “heavy” and to retain moisture longer. Sandy soil, on the other hand, will drain more quickly. Some natives favor one type of soil over the other. The amount of moisture typically in the soil is also important. Soil described as “mesic” has a moderate and well-balanced supply of moisture, while dry soil and wet soil are fairly self-explanatory. The amount of sunlight the site receives – full, partial or none – is also an important factor to be considered.
It would not be unusual to see more than one of these at any given site. On the one-third acre restoration on our property, the entire piece has full sun exposure and heavy clay soil, but soil moisture runs from mesic to wet, with a spring-fed creek running through the middle of the site.
While selection of the prairie natives that will go into your site is largely an exercise on paper, preparation of the restoration site is where the “sweat equity” investment begins. The optimal time for a native wildflower seeding in the upper Midwest is late Fall or early Winter, meaning site preparation should begin in the preceding Spring. There are two things that must be cleared away: vegetation and the “seed bank” on and in the ground from previous growing seasons.
Mowing, tilling, and burning are all options for clearing vegetation. As a general rule, tilling the site is not considered the best option because opening up the soil makes it much easier for “undesirable” seeds to take hold. Mowing will get the vegetation down to the ground and the roots will still hold the soil to prevent erosion, but the legacy vegetation is not killed and could come back. A controlled burn will remove the vegetation down to the soil and could kill off those plants will more shallow roots. Of course, a controlled burn is more complicated and requires specialized experience, expertise and tools. Of course, one should follow the local rules and regulations regarding a burn, and notifying the local fire department in advance of the burn would be a good idea. All things being equal, a controlled burn is the preferred method for clearing a site of legacy vegetation. However, that is only the first step of site preparation.
Once the site is initially cleared, seed and rootstock in the soil will quickly spring to life. Be prepared to take steps to clear out this new growth, perhaps more than once. The most effective way to clear out this re-growth is with a low-impact glyphosate-based herbicide. If the initial vegetation load was cleared with a spring burn or mowing, plan on doing two herbicide treatments through the Summer months before doing the Fall seeding.
Late Fall or early Winter are a good time to put out the seed for a native wildflower planting, especially in the northern tier states. Most seeds require a soil temperature of 60°F or greater in order to germinate, so this means the seeds will lay fallow for the Winter, germinating in the Spring. Since many forbs require a period of cold and wet treatment called “stratification,” a Fall/Winter seeding works quite well. Second best option for seeding time is late spring, after the first weeds have a chance to germinate and then be removed.
Bare dirt without tilling is the best surface for the seeding. As noted earlier, tilled ground offers a nice bed for new or existing “undesirable” seeds to germinate. If the site is prone to erosion and a fall seeding is planned, the erosion risk can be mitigated with a late Summer seeding of oats or some other annual. The oats will quickly germinate, holding the soil and keeping undesirable plants at bay. The wildflower seeding can be done right on top of the oats before the first killing frost.
There are a number of ways to distribute the seed, with the best method depending on the size of the restoration site and your access to specialized seeding equipment. Organizations that routinely do large-scale restorations often have a seed drill machinery that functions much like the name suggests. This equipment is usually out of reach for most of us. With a small restoration, perhaps a couple of acres or less, hand-broadcasting the seed is a viable option.
The seed should be mixed with filler material, to give a good mixture and to provide some volume for more even distribution of the seeds. Sand, dirt and sawdust are all acceptable fillers. Mix the seeds and the filler(s), put it in five-gallon pails and start throwing it out on the site. It will seem rather futile, and you will probably question whether you are getting a good distribution or if this will even work.
One good way to insure even distribution is to use a very visible filler. Something light, like white sand or kitty litter work well because you can see where you’ve seeded or missed.
Don’t worry – it will work!
What to Expect When Expecting Prairie Wildflowers
Do not expect any of the native wildflowers to show up during the first growing season. Those plants are there, but they are germinating and must first grow down in order to group up. Instead, the “undesirable” plants will likely reappear in season one. As satisfying as it might be, resist the urge to pull these out by the root – the small tender wildflowers just getting started might also be pulled out. Instead, mow all vegetation at the highest setting on the mower and do not let the undesirables bloom.
The second growing season is probably when the seeded wildflowers will start to appear. This is when hope rises, when the doubts you had when hand-broadcasting the seed disappear. Once beyond the second growing season, it would be fine to mow the site once blooming is done at the end of the season. Eventually, after the fifth year or so, a Spring burn would be helpful to remove the accumulated plant debris.
Do not be surprised if the composition of wildflowers shifts after a burn. Some of the natives might not be obvious until a burn gives them room to show off. In our case, the Compass Plant did not become evident on our restoration until the fifth growing season. Each season the constellation of blooms will change. Some species will flourish early and then dwindle in numbers as other species become more prevalent. With or without a burn, the floral makeup of your new prairie will change from year to year, giving your honey bees a new pantry every year.
1Where the Sky Began, John Madson, Unniversity of Iowa Books, 1982
2National Park Service, U.S. Department of the Interior, http://www.beatricene.com/homestead/prairie.html
3Rufus Isaacs et al, Journal of Applied Ecology, Vol 51, Issue 4, pp 890-898