Flax Pollination and Isolation Part One

I am so far behind on writing about my flax project that it’s hard to know where to start. If you and I have spoken in person since last Friday, you already know about my rodent apocalypse. However, rather than skipping too far ahead in the story here on my blog, I will try to reconstruct events chronologically in the next few posts.

Back in April I did a lot of reading about flax pollination, because the two main goals of our study group’s flax germplasm project this year were:

1. To increase the quantity of seed we have of each of the varieties Carolyn requested from the USDA (they send 200 seeds).

2. To prevent the varieties from cross-pollinating so that we can grow them again next year and evaluate the different cultivars for a number of traits including height, branching, and fiber quality.

When I first began to think about how to keep the varieties isolated, I started with my own observations and assumptions. I have many photos of bees and other insects visiting my flax flowers (and many more pictures of blurs or nothingness which I swear *were* bees or other flying creatures). You can see an earlier blog post about that here. So, I imaged that I needed to separate varieties as far as a bee might fly. Well, honey bees can fly really far, like 5 to 7 miles, which would mean I would need to plant each type of flax in a different town! When I visualized myself driving to twenty-five to thirty far-flung places around Western MA to weed, water, photograph, etc., it became obvious that it wasn’t a feasible design for this project.

So, I did some research, and enlisted the help of Carolyn, the USDA folks, and other flax growers. It was extremely interesting and informative to read up on isolation but also frustrating. We encountered a very wide range of recommendations and practices.

Despite many years-worth of experience and observations in growing flax, I have practically no experience with saving flax seed and none at all with isolating different varieties from one another. However, I’m familiar with several strategies that seed savers use to keep vegetable varieties isolated. For example, you can separate plants by distance, use physical barriers, or separate by the timing of planting and flowering. I had hoped to find a “best practices” set of guidelines for fiber flax, but alas I did not encounter such a thing.

In our research, the distances cited to prevent cross-pollination included (from least to greatest): 10 cm, 5 feet, 3 meters, 7 meters, and 35 meters. These were just distance recommendations, without any physical barrier. A couple of the studies were concerned with out-crossing of GM oil-seed flax crops, not fiber flax, and were specifically trying to measure a phenomenon described as “gene flow”. To my knowledge, no one is trying to create GM fiber flax, thankfully. However, I figure the research is still relevant insofar as we’re trying to prevent two types of plants from crossing by keeping them separated in an effective way.

Botanists regard flax as self-pollinating, and flax flowers are considered “perfect” (which is a sweet way to put it) meaning the structure allows for self-pollination and does not rely on other factors. There does not seem to be a consensus on the role of other factors such as wind or insects except that it’s variable from year to year and site to site. Flax pollen is considered “heavy” and thus not especially wind-borne, and on the whole flax is not considered very appealing to insects. I did find mention of honey bees, bumble bees, and thrips, but no definitive ideas about how much their visits contribute to pollination. (NB Recent conversations with a local entomologist have only complicated matters, because apparently flax *is* preferred by some species for nectar, but it’s unclear how much that might impact pollen transfer. Also, my closer observations of insects on flax this summer suggest that actually bumble bees and teeny, delicate flying creatures are the main visitors, not honey bees after all).

It was helpful to know that much lesser distances than 5-7 miles could keep the varieties isolated. However, with such a wide range of guidelines, it was difficult to know how to proceed.

Long story short, I decided to use a physical barrier, and to build isolation cages. In theory, these would prevent both wind and insect pollination, allowing me to plant a lot of different varieties in close proximity. That’s what I did.

At the USDA station in Ames, Iowa, they construct isolation cages with mosquito or no-see-um netting, and these are inside greenhouses. I was hesitant to order either of these types of netting because I honestly wasn’t sure how much I would need or exactly how I would make the “cages”.

Fortunately I found an alternative that allowed me to tinker and experiment. A million thanks to Ryan at Many Hands Farm for his generous contribution of a roll of light-weight Agribon row cover, and to Bernard at Amethyst Farm for putting us in touch. The row-cover worked fine for keeping insects off. As Ryan pointed out, it also may have had the added benefit of slightly shading the flax to off-set the heat of July.

Next up, photos of cutting, sewing, setting up, and repairing the isolation “cages” ….