Every year, the High Mowing Production Farm reliably produces many varieties of quality seed for tomatoes, peppers, cucurbits and some species of Brassicas. This past year we grew seed for 46 varieties including: Ali Baba watermelon, Long Pie pumpkin, Tom Thumb popcorn, Jack Straw pumpkin, Indigo Rose tomato, and My Fair Lady F1 & Bling F1 sweet corn. Although we wish that we could grow most, if not all, of the varieties that we offer, it just isn’t feasible in our region because of both our limited space and our climate.  Growing for seed requires a lot of land with many isolated fields separated by at least a half mile (depending on the crop) so that related varieties can’t cross.  Our other major challenge is our climate.  Our cold and often damp climate can prevent some seed crops from fully maturing.  Over the past few years we have started doing some smaller experiments, or test productions, to push our boundaries and continue to increase our knowledge of seed production.

Seed Crops that are Most Challenging for Us: Biennials

Producing seed for biennial crops (see our recent article on this) poses a challenge in our harsh New England climate.

Biennials such as Brassicas require vernalization—a prolonged period of cold temperatures—to trigger the plant to flower and ultimately to produce seed. 

Biennial plants best overwinter in temperatures that hover near freezing.  The premier climate for growing biennial seed crops is best showcased by the mild, wet winters followed by hot, dry summers of the Pacific Northwest, from where we currently source many of our biennial crops. In that region, Brassica crops such as cabbages are seeded in the fall and overwintered in the field.  In early spring they break dormancy, flower and produce seed in the height of the (hopefully) dry summer when the threat of disease brought on by moisture is lessened.

In any given year on our Seed Production Farm, we produce about a dozen Brassica varieties, including: Ruby Streaks, Green Wave, and Garnet Giant mustard greens as well as Asian greens such as Prize Choy, Vivid Choi Pac Choy, and Shanghai Green Pac Choy. Unfortunately, we can really struggle to get high yields out of our crop due to several factors:

  • Our winter temperatures can simply kill the plants, rather than vernalize them. Prolonged periods of sub-freezing temperatures such as those typical of northern Vermont, do not provide the best climate for biennial crops to overwinter right out in the field, even with row cover.  Currently, the Brassicas that we plant for our seed productions are seeded in the greenhouse in very early spring.  They are then hardened off and transplanted in the ground long enough to trick them into thinking that they’ve had a full winter—as long as the weather cooperates!
  • We have trouble with complete vernalization and therefore have had non-uniform flowering and lower seed yields. Because of the ways that we push vernalization of our Brassicas, different plants can reach different levels of vernalization.  This causes Brassica plants to flower at different times and therefore yield less seed, due to something called “self- incompatibility”—a trick that Brassicas use to decrease inbreeding—they will not self-cross, or cross with other plants that are too genetically similar.  While this is a beneficial trait for the plants, it makes it even more important to have the stand flowering uniformly to maximize the opportunities for pollination.
  • We can have cool, wet summers.  These types of conditions can pose challenges with disease, and can make it difficult for plants to be nicely dried down for threshing.


Why do we grow these crops if they are so challenging? 

Seed Production of Golden Frill Mustard in our Hoop House

We really think that it’s important to try and improve on our seed production systems here at HMS, because there are a lot of opportunities for us to improve what we do, and also because many other farmers in the region have interest becoming more seed self-reliant.

We also know how important our stock seed is.  Being able to grow stock seed in our climate is really important for controlling the quality, even if we don’t grow an entire seed crop.  Not to mention that it is also fun and challenging top push our knowledge and boundaries!


Test Productions Take on our Climate and Space Challenges

Planting into a Controlled Environment

By creating a more controlled environment to grow some of these biennial crops, over the past few years we have been able to get to know the limits of certain varieties.  By providing minimal protection to the elements by way of row cover and unheated hoop houses, we can control moisture and take just enough of that cold away to overwinter some varieties.  In past test productions we have also planted Brassicas in the field and covered with row cover but these plantings did not survive as well, or yield seed as well as hoophouse plantings.

Experimenting with Plant Size

You may have noticed that your later fall-planted arugula or lettuce can hold up better to the first frosts than more mature plants of the same varieties.  We succession-plant test crops to pinpoint optimal planting dates for crops so that they are small enough to tolerate the cold temperatures, yet large enough to “register” vernalization. During the four years we have run test productions, we have experimented with different planting dates with varied results.  For instance, in 2011 a crop of Shanghai Green seeded in the greenhouse on September 5 and transplanted in the hoophouse on October 10 was overly mature and killed by winter temperatures, while a second succession seeded and transplanted two weeks later were young enough to tolerate cold temperatures and produced seed in the mid- to late-summer.

Determining the Possibilities and Limitations for our Seed Production

By playing with plant varieties, sizes, spacing, timings, and treatments, every year we get a little better at dialing in to the possibilities for seed production here.  Our test productions have the potential for identifying how to minimize plant loss, achieve uniform vernalization, getting earlier seed crops with an extended season, and increasing our seed yields significantly.  For instance, Shanghai Green Pac Choy typically yields 34 pounds of seed, per 1000 plants in the field, but our optimal test productions of this variety have yielded 100 pounds per 1000 plants in the hoophouse.  Because we can control the moisture in the hoophouse, we can also plant at twice the density as in the field.  This means with tighter spacing and increased seed yield, there is the potential for up to six times the seed yield for this variety—or one sixth of the space, if grown under cover.


These test productions could inform us for doing productions of rare and/or hard-to-grow varieties, such as Rosalind broccoli, which has been particularly difficult for us to get seed from.  Growing under cover could also provide more options for closer placed isolations, if we fit hoop houses with isolation screens.

Exploring the specifics is important to determine whether if it is cost-effective as well.  So far, working within our small hoop houses means doing everything by hand.  As these test production tell us more, we can continue exploring more mechanized ways of doing seed productions, and options for using existing infrastructure on farms.

We hope that someday soon, the test productions will give us enough information to effectively predict and control climate variables and produce quality organic seed at quantity large enough to justify costs.  We hope to gain enough information through these test productions so that in the future more small farmers in New England will find it economically viable to grow seed utilizing mostly existing infrastructure.  As we become more comfortable producing seed using these methods we will be glad to share this knowledge with growers.  We’ll share more about our test productions as we continue to learn!