Cleaning Brassica Seeds

With snowy times upon us; and my regular work hours tossed around by a combination of families, friends, holiday seasons, and cross-country skiing; and putting together our 2011 seed catalog; I’ve had a bit of trouble scheduling in some computer time to write a new post. I thought it might be easiest to look back to the growing season and wrap up 2010 with a post about cleaning brassica seeds -  our biggest seed crop both in area grown and amount  harvested.

Cleaning dry seeded crops (like brassicas) usually consists of three activities:

  • Threshing
  • Screening
  • Winnowing

Let’s start off where we left when we last talked about brassicas

with piles of plants laid out on tarps in the barn. The plants stayed there a few weeks continuing to dry and mature.

In September, on a sunny Friday around 3 p.m. when we ran out of other things to do (i.e. gave up on that week’s to-do list) we put on our gloves and got


There are different machines that can be used to thresh seeds. However we thresh by hand.

We all stand around and rub the seeds off of the stems into Rubbermaid bins. Processed plants go into a wheelbarrow and then to the compost.

Do notice everyone is wearing gloves – saving seeds is asking for small (and not so small) cuts and splinters.

We always thresh on a tarp to catch the seeds that shoot everywhere. We empty the tarps in the Rubbermaid bins of chaff and seed.


Next we separate the big pieces of chaff from the small pieces of chaff, seeds, and dust …

by pouring the contents of one Rubbermaid onto a screen placed over another Rubbermaid. We shake the screen to let the seed fall through and then transfer the big bits to another bin destined for the compost.

We repeat the process with a smaller screen.

Gradually we remove most of the chaff. We transfer the large bin into a small container and proceed to


In this step, we clean the heavy seeds by blowing out lighter material.

Two fans each with 3 speeds give us a number of different wind speed variations. We start on a low setting and if it isn’t strong enough, we try again with a higher speed.

Always try to pour an equal steady stream in front of the fans.

We winnow over multiple bins on a tarp in case the fan blows a bit too hard and the seeds go flying. We also like to see what is being removed from the seed lot.

We alternate screening and winnowing multiple times to get the seeds as clean as possible.

We spread the clean seed  on trays or tarps to let it dry a week or two, before one last winnowing and then pack the seeds up.


Speaking of brassicas, I recently read a blog post at subsistence pattern about winter gardening in low tunnels in Northern Idaho with great pictures of brassicas and other hardy crops.

And speaking of winter growing, the veggie patch re-imagined has a series of posts on overwintering hot peppers indoors.

I’ll probably post shortly about cleaning beans.

Happy New Year!

15 thoughts on “Cleaning Brassica Seeds

  1. On seed saving, I’m curious as to your thoughts on the viability of fully formed but still not totally dry “green” seed that is allowed to dry away from the garden. I saved a whole lot of parsley seed before this fall’s bad weather set in and am hoping they will still have good germination rates. This is often an issue in our short season and I sometimes wonder if it really makes any difference wheather I leave fully formed seeds to dry on the plant in the garden or pull them for drying on our porch.

    I like how you used double fans and more than one tote…I will keep that in mind for next falls seed harvest.

    1. Hi Mike,
      Sometimes fully-formed green seeds might be viable but they might not be as vigourous or keep their germ as long, as if they had been left to mature on the plant. Though the best seeds usually mature in the field, seeds that are left on pulled plants will keep ripening and achieve better quality than by simply threshing green seed.
      Weather is one reason to pull plants. The other reason is that on some plants the seeds mature gradually – unharvested mature seeds will often shatter as you wait for the rest of the seeds to dry. I pull plants when about 2/3 of the seed is ready and hope that most of the remaining seeds will mature indoors.
      I usually winnow seeds pretty aggressively to remove lighter seeds that aren’t as potent.
      Of course, if all I can harvest are green seeds, and the variety is important to me, I will do so; but I usually will only use this seed on farm and won’t sell any of it.
      I love using double fans. I saw this at the Organic Seed Alliance conference in 2008 and adopted the technique immediately.

      Thanks for the questions,

    1. Hi Mike,

      We start with 1/2″ screens then use 1/4″ screens. This sequence removes a lot of the chaff.

      After winnowing we use window screens for very small seed like amaranth.

      After these steps the seed is usually quite clean.


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