Brassica Seed Harvest – Mizuna Time!

My head has been full of garlic lately – garlic scapes, garlic bulbils, and currently we’re knee deep in garlic harvest – but the end of July also happens to be annual brassica seed harvest time!

Last week, we pulled in a big Mizuna seed crop. Today, to celebrate the occasion we’ll talk brassicas, specifically

  • Different brassica species and biennial vs. annual seed production
  • Growing annual brassicas for seed
  • Harvesting brassica seed

Brassica Species and Biennial vs. Annual Seed Production

The Brassicacea family (Brassicas for short) contains multiple species:

  • Brassica Oleracea (broccoli, cauliflower, cabbage, some kales, and more!)
  • Brassica Napus (other kales and rutabage)
  • Brassica Rapa (chinese cabbage, turnips, rapini, mizuna, …)
  • Brassica Juncea (spicy mustards)
  • Eruca Sativa (arugula)
  • Raphanus Sativus (radishes)

Each brassica will only cross pollinate within it’s own species – i.e.a B. Rapa won’t cross with a B. Juncea. As such, you can grow one type of each species side by side. Brassica seed also stores quite well. I grow enough seed of each type to last about 3 years before I will have to grow it out again.

This year I am growing Mizuna as my main annual Brassica Rapa. Mizuna is a mild Japanese green with a slight bite. It can be eaten in raw salads or stirfried but it is also great as a pickled condiment.

All brassicas can be grown as biennials (planted in late summer and overwintered to produce seed in their second year) but only a few can also be grown as annuals (leafy B. Rapas, B. Juncea. Arugula, Spring Radishes and short season Broccoli and Cauliflower). On our farm we grow quite a bit of overwintered brassicas, which also happens to mature about a month earlier than annual brassicas (see this post for our overwintered brassica seed harvest and this post about growing out radish seed as an annual.)

Growing Annual Brassicas For Seed

Annual brassicas are a lot easier to grow than biennials since you don’t have to worry about plants dying over the winter. The only trick is planting early enough for seed to mature, but not so early that plants suffer from severe cold snaps.

May 1st, we transplanted the Mizuna.

Early June, the plants were established and had sized up.

End of June, Mizuna is in full blossom. I usually assume that brassica seed will be ready to harvest about a month after they flower.

Early July, flowering was over and green seed pods were on.

Last week, the fields were drying to a nice brown. Well, except for the green weeds that exploded in the heat, despite weekly weeding. (This is a case of do as I say not as I do.Earlier this Spring, I posted on the importance of good weed control in seed production.)

Harvesting Brassica Seed

We cut the plants with secaturs and stuffed them (ever so delicately) in rubbermaid bins.

We brought in three wagonloads of bins.

And now, the Mizuna is sitting on tarps in the barn waiting to be threshed. (Not pictured in the photo are the fleet of fans on ventilation duty.)

I will wait for a nice dry sunny day to thresh the Mizuna. Hopefully sooner than later, but we’ll have to fit threshing inamidst garlic and onion cleaning and grading, the weekly seed tomato harvests, and all those other August tasks!

I’ll keep you posted on the brassica front.

14 thoughts on “Brassica Seed Harvest – Mizuna Time!

  1. Hi Dan,

    Nice post. It reminds me of what you were saying today that you were missing in the early stages of your agricultural education- an easy calendar with the general tasks outlined in overview. I’m sure many (including myself!) will find it quite helpful. I liked the hot tip, too, about being able to expect seed ready about one month after flowering.

    See you tomorrow,

  2. I know this post is very old, but it’s the closest page i could find on the internet, with a light-medium amount of searching.

    I live in California, and my Red Mizuna is starting to produce large and healthy looking seed pods! I have about only 6 plants (i’m growing in my backyard) and saw the bees go from one to another to another all month, so i know they’re fertilized.

    My question is: i have no idea how to harvest the Mizuna for seed for next year, how long do i wait before cutting them down, and how long do they dry out? i literally have not an inkling of what to do! thanks for your time, and your help!

    please email me a response at “casualty of civilization AT gmail DOT com” without spaces! 🙂

    Dylan, zone 9-10!

  3. Hi Dylan,

    The mizuna plant will tell you when it’s ready to be harvested. You’ll know the plants are ready when the pods turn yellow brown and they shatter when you handle them.

    For six plants you don’t have to cut the whole plants the way we do for hundreds of plant
    Instead leave the plant standing in your garden. You can bend each plant into a paper bag or a bin and shake the plant around. The mature seed will be collected in the bag and the immature seed will stay on the plant. Do this every 3-4 of days until all the pods have shattered or you get tired of collecting seed.

    You can clean the seed as you collect it or you can gather all the seed and dry pods until you’ve harvested everything off the plants.

    To clean the seed: use a colander or 1/4″ screen to separate the pods from the seed; then winnow the seed by pouring the seed from one container to another outside on a windy day – the wind will blow the dust away. You can also read more about cleaning brassica seed (mizuna is a brassica) at this post:

    Good luck!

  4. i am an agriculture teacher. i have started transplanting mizuna seedlings in containers. this is the first time i come across such plant here in the manila.

  5. Thank you so much for the time frame! This lets me know that for my tiny garden, watering daily (probably twice a day in our heat) for roughly two months just to get a $3 packet of mizuna seed is not worth it! Better to buy and let others like you do the work!

  6. Thank you for sharing this. This year I have been experimenting with trying to make grocery store veggies last. Much of is has been working, the leeks were most impressive. Since I have grown potatoes in the past I thought I would try my favorite, turn ups, but had no idea how they grow. I have found that cutting the tops (a bit of the root with the new greens growing in) and placing it in water for a week or two allows the plant to grow roots. Then I placed that in dirt. Eventually they flowered but I wasn’t sure when I would spot the seeds. I found out in another blog of yours that the flowers are edible 😎👍 Today I found the seed pods! So again, thank you for sharing. Very helpful.

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