Organic & small-scale seed crops

Harvesting seed crops

Here at DBF about half of the farm’s income comes from seed contracts with a number of different seed companies.  I’ll be learning a lot about how to produce organic, open-pollinated seed crops this summer.

Growing seed crops is a bit different than growing food crops because the plant must go through all of its life stages, including pollination and full seed formation.  Then, the seeds must be harvested and cleaned before they are ready to be sold or packed away for next year.  This entire process involves careful planning and observation in order to ensure that the crop has proper conditions to produce healthy seeds.  Like food crops, seed crops require various growing conditions, harvesting methods, and storage conditions.  These traits tend to be similar across plant families.

In the past two weeks I got my first look at harvesting seed crops when we cut the turnip seeds in DBF’s back field.  Turnips are in the brassica family (broccoli, kale, cabbage, radishes, mustard greens, etc) and are more specifically in the brassica rapa species (along with broccoli raab and napa cabbage).  Turnips are an example of a biennial plant, which means it typically takes two seasons to go through its life cycle.  Such a life cycle might look like this: plant growth occurs in the first season, the colder winter follows as a period of energy storage for the plant (in the case of turnips, this would be in the roots), and when it warms up in the second season the plant completes its life cycle with flowering and eventual seed formation.

In a process known as bolting, turnips flower by extending a middle stalk much farther upward than the rest of the plant.  The flowers must be pollinated by insects that carry pollen from one plant to the stigma of another plant.  If all goes well, the pollen will germinate and develop into a viable seed.  In turnips and most other brassicas, this completed seed pod is skinny and oblong (a couple inches in length) with a tough skin. 

Steve planted DBF’s turnip seed crop last October.  It flowered this spring.  We allowed the seed pods to dry in the field so that all of the pods turned from their initial green, tough pod to a dry, tan pod.  We then went into the field to cut the seeds.  

turnip seeds ready for cutting

We trimmed the entire stalk of the plant that has seed pods on it, laying them on big denim sheets, and then carried them up to the barn loft to lay them out for their final curing.

We turned the stalks daily for about one week to help with the drying process.  Once the seed pods were completely dry, we could shatter the pods by walking over them.  The seeds fell to the bottom of the tarp.  Then comes the cleaning process:  removing the chaff (all of the dry plant material like the pod shells that no longer are needed) and any nonviable seeds.  This is a multi-step process which involves sifting the material through a variety of screens of different sizes and using a fan to do the final winnowing.

Steve sifting out chaff

A close-up look at the remaining seed & chaff

These seeds still require a final winnowing.

The end product should be about eight pounds of turnip seeds, which Steve will be selling to Southern Exposure, a seed company based in Virginia.

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Update: In the few days after I wrote this post and before I could upload it, we began cutting the broccoli raab seed crop.  It’s very similar to the turnips because they’re in the same species.  This time we have many seeds to harvest- the big goal is 100 pounds of seed!  Here are some photos to get some perspective.

raab seed pods

We made a nice dent in the field after one day's work.

We will fill the entire barn loft with seed stalks this time.