Organic Broadcaster

Farm couple takes pollinator conservation to higher level

By Eric Lee-Mäder, Xerces Society

Vilicus Farm 3

To attract native pollinators like this ground-nesting Eucerine bee, the Crabtrees worked with the Xerces Society to seed their buffer areas with more than 20 species of native grasses and wildflowers, including plains coreopsis shown here.
Photo by Jennifer Hopwood, Xerces Society

“We want to implement pollinator conserva­tion at the field-level scale.” I’m having lunch with my friends Doug and Anna Crabtree at a Portland, Ore. diner where Doug is holding the floor. “Anyone can create a small wildflower strip, but as we scale up, we need conservation areas distrib­uted across the entire operation.”

Doug’s vision is not small, nor are Crabtrees’ initial accomplishments. Farming more than 1,500 acres of dryland organic field crops in north­ern Montana, Doug and Anna have already integrated huge, expansive wildflower buffers between their production fields. Yet if you ask, they’ll tell you that they’re just getting started.

I first met Doug and Anna at a very snowy organic farming confer­ence in Washington state in early 2012. They had a strong land ethic and were working with their local National Resources Conservation Service (NRCS) office to explore different conservation options. Talking with them about pollina­tors at the conference however, we began to see a larger model for ecosystem-based farming unfold.

While it’s true that many of the Crabtrees’ more than 15 crops, such as black emmer and einkorn wheat do not require insect pollination, others like flax, safflower, and sunflower benefit greatly from bee visitation, especially visitation by wild bees.

In fact, in the most ground-breaking and com­prehensive study of its kind, more than 40 of the world’s leading pollination researchers pub­lished a major report in the journal Science ear­lier this year with the finding that pollination by native wild bees—such as those supported by the Crabtrees’ habitat—increased yields in all of the crops studied, while pollination by the domesticated honey bee only increased yields in14% of those same crops. The report also noted that in crops with demonstrated yield increases by both groups, wild bees increased yields twice as much as honey bees. More than 40 crops were reviewed in the analysis.

Working with the Crabtrees, we quickly began to tally up a list of other benefits that the wildflower habitat on their farm is providing. For example, one of Montana’s most significant grain pests, the Russian wheat aphid causes millions of dollars in annual crop losses to the state’s farmers. Yet, as extensive research now demonstrates, wildflower habitat near grain fields yields an enormous payoff in natural pest control by increasing populations of more than a dozen species of tiny parasitoid wasps that at­tack the aphid. The Crabtrees’ growing network of wildflower buffers also provide value by re­ducing wind velocity for adjacent seedling crops, reducing overland surface water and sediment runoff, and capturing wind-blown weed seed before it can settle in production fields—plus, the buffers themselves are just plain beautiful!

While the Crabtrees’ wildflower buffers are clearly paying dividends today, early in the design and establishment phase we faced a number of pragmatic feasibility questions. Spe­cifically, could we establish high quality native wildflower habitat using only organic methods? Also, what was the optimal seed mix for the buffer areas—one that would resist weeds and persist over time? And, when was the ideal planting time for a non-irrigated landscape averaging less than 12-inches of precipitation annually?

In tackling the first of these questions, we were confronted by the fact that most successful prairie restoration—which is in essence what we were doing—is heavily dependent on conven­tional herbicides to remove the baseline weedy plant community and create a clean slate for native plants to grow without competition. And, the Crabtrees’ field edges certainly had weeds. The most significant of these was a dominant cover of non-native crested wheatgrass—a rangeland plant initially introduced from Siberia for its wildly successful ability to completely takeover cold, low-precipitation landscapes. I knew from experience that simply drill seeding native wildflowers into the crested wheatgrass would be a waste of time and money. We had to create a new plan, one without precedent for me as a restoration practitioner.

After a lot of head scratching with my Xerces Society colleague Jennifer Hopwood, we worked with the Crabtrees to design a series of replicated tillage trials to understand which cultivation strategies would be most successful at suppressing future re-growth by the crested wheatgrass and provide a clean seedbed for our natives. The trials included wide chisel plowed swaths to open up bare ground strips that we could re-seed into, as well as another set of treatments where we used deep moldboard plowing to invert the entire sod layer and create a totally barren, grass-free surface. The moldboard treatment worried me a lot, espe­cially with the high potential for wind erosion on the northern plains. Yet, by summer 2013 it was clear that the moldboard treatment was an overwhelming success. There was little to no re-growth by the crested wheatgrass, and without competition, the native plants grew fast and prolifically enough to protect the soil.

A well-designed conservation buffer can provide multiple benefits to a farm, ranging from soil and water protection to natural pest control from the beneficial insects that the buffer exports into adjacent crops. Photo by Jennifer Hopwood, Xerces Society

A well-designed conservation buffer can provide multiple benefits to a farm, ranging from soil and water protection to natural pest control from the beneficial insects that the buffer exports into adjacent crops.
Photo by Jennifer Hopwood, Xerces Society

With some hindsight, I think a key part of our success was a thoughtful approach to answer­ing another of our initial questions: “What is the optimal native plant seed mix for this piece of land?” Of course our goal was a wildflower-rich plant community, but wildflower-only seed mixes are prone to weed encroachment since native grasses help occupy the space and the root zone between wildflowers to form a tight living mat that resists weed invasion. With this in mind, we included several species of low-stature native grasses at almost 15% of the seed mix—including both warm season and cool season species to fill any ecological void that a weed might otherwise occupy.

For the flowers in the seed mix, we looked to the most drought-adapted Western native species for which we could find seed sources. Lewis flax, blanketflower, Maximilian sun­flower, yarrow, scarlet globemallow, and others formed the foundation of the seed mix, which we wanted to be resilient in the face of the toughest climate change conditions that the Crabtrees might ever face. The inclusion of some annual wildflowers like plains coreopsis and wild sunflower helped provide immediate beneficial insect value and rapidly covered the soil to prevent erosion. All of this was planted in late spring, immediately after plowing, and just before the area typically receives most of its rain.

The results of this process have been wildly successful. In addition to having most of the species in our seed mix establish, the buffer areas are showing little weed invasion, few spaces for new weeds to occupy, and immedi­ate colonization by beneficial insects, includ­ing many species of wild bees and beneficial predators like soft-winged flower beetles. Complementing these wildflower buffers, the Crabtrees are using extensive multi-species flowering cover crop rotations that build soil organic matter, disrupt pest and disease cycles, and help create seamless corridors for benefi­cial species to move throughout the farm. The net effect is a carefully orchestrated ecosystem that provides its own pollinators, its own pest control, and its own nutrient cycling.

While we’ve made amazing progress so far, there’s a lot more to do, as Doug and Anna will readily point out. In addition to wanting to expand their operation with more land (and hence more habitat), Doug and Anna are committed to mentoring new farmers through an apprentice program. They see this type of conservation expertise as one of the core skills they want their apprentices to gain. Ultimately when those apprentices go on to establish their own farms, Doug and Anna hope that they will bring these ideas along, and a new generation of ecosystem-based farmers will take root all across the northern plains.

Eric Lee-Mäder is an agroecologist and author of the books Attracting Native Pollinators, and Farming with Beneficial Insects through Storey Publishing. He is the Assistant Pollinator Program Director at the Xerces Society, and an Assistant Professor of Exten­sion at the University of Minnesota’s Department of Entomology. He blogs at


January | February 2014

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