How to Save Mustard Green Seeds for Planting

It seems like you only have to look away for a second, or maybe a day, and your mature mustard greens will start flowering.

And not long after that, they’re full of seed pods.

In some circumstances you can collect the seeds and save them for replanting next season or to share with friends.

A close up vertical image of a bright yellow flower pictured in light sunshine on a soft focus green background. To the top and bottom of the frame is green and white printed text.

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Mustard greens are a cool-weather crop, usually grown in the spring or fall and are typically ready to harvest after 30-60 days, depending on the variety.

The most popular types to grow for the spicy, flavorful leaves are Brassica juncea, B. rapa var. japonica and B. rapa var. narinosa.

You can learn more about how to grow mustard greens in our guide.

In this article, I’m going to cover how to save seeds from your mustard greens for planting.

Planting Considerations

When mustard greens bolt the leaves become excessively bitter, putting an end to your harvest.

The plants send up flower stalks with small yellow blooms. After the flowers have opened up, they attract pollinators, and after pollination the pods start to form.

A close up horizontal image of a bee about to land on a yellow flower, pictured in light sunshine on a soft focus background.

If you are intending to harvest the seeds, you need to keep in mind that mustard greens can cross-pollinate with other varieties of the same species, and if that happens, the saved seeds won’t grow true to the variety you planted.

Mizuna, for example, is a variety of B. rapa, as are all types of turnip. If you have turnips growing nearby, you run the risk of cross-pollination.

There is no danger of cross pollination between different Brassica species, so you don’t need to worry if you are growing kale or cabbage nearby.

If you are growing a hybrid variety, plants grown from saved seed will not produce true to the parent plant. So check your seed packet to make sure the cultivars you have chosen are open-pollinated or heirloom varieties.

A close up horizontal image of a yellow flower head pictured in light sunshine on a soft focus background.

In addition to cross pollination, if the plants are exposed to wild mustard or other cruciferous weeds and volunteers, certain pathogens like Colletotrichum higginisianum that causes anthracnose, can make their way from the infected wild plants into your cultivated greens.

The plants can then produce infected seed and spread the disease to the next generation of plants. This is thankfully quite rare, but if you suspect a transfer of infection, that’s a good reason to purchase a new packet of seeds instead of trying to save them from your plants.

If you’re not growing related plants and are fairly certain you don’t have an issue with disease or volunteers, the seed-saving process is fairly simple.

Timing is everything, so keep reading to learn when to make your move.

When to Harvest

As with any member of the cabbage family you grow in your vegetable garden, it’s particularly important not to plant mustard greens in the same place two years in a row. And you shouldn’t plant any of their Brassica relatives in that same spot, either – such as broccoli, turnips, or kale.

A close up horizontal image of bright green, mature leaves growing in the garden pictured in bright sunshine.

I understand if you’re wondering, “What does this chatter about crop rotation have to do with saving seeds?” The answer: If you allow these spicy vegetables to go to seed in the garden, you risk having volunteers grow in that same space next year.

Then you’ll be establishing a haven for Brassica insect pests and soil borne diseases. Instead, make sure to harvest before the pods start popping.

A close up horizontal picture of pods developing on a plant pictured in light sunshine on a soft focus background.
Unripe pods not ready to harvset.

But you can’t do this too early, as the seeds won’t be viable if you pick the pods before they are ready.

You need to allow the pods to dry and turn brown on the plant. To make sure they’re ready, slit one or two of the pods open and make sure the seeds inside are brown, or in the case of some varieties like red leaf mizuna, a dusty rose or plum color.

If they’re green, light green, or white, they aren’t yet ready to harvest.

The pods may not all dry out at the same time, those closest to the base of the flower stalk tend to dry first. You can pick these off individually or simply wait until most of the pods on the stalk are ready. Some of the drier pods may split and drop their seed.

Separating and Storing

To save mustard green seeds, you can remove the dry pods individually, cut off the entire branch, or you can pull up the plant.

A close up horizontal image of dried pods ready for harvest.

Carefully separate the pods from the flower stalk and set them on a drop cloth or in a shoebox or bucket. Some of the seeds will drop out of the pods on their own.

For the others, you can rub the dry pods between your thumb and forefinger to release them.

If you have a huge batch, you can set them out on a clean sheet or tarp and walk over them with clean-soled shoes until the pods pop open and release their contents.

Remove large pieces of chaff and debris by hand, and separate the rest by winnowing.

A close up horizontal image of small round dark brown seeds on a white background.

Discard the stalks or spent plants, whichever you cut for the harvest, and the chaff.

Store the seeds in a small craft paper envelope, a jar with a screw-on lid, or a plastic storage container. Be sure to label the storage container with the date of collection and the variety.

Place them in a cool dry place and they should stay viable for up to four years.

Mustard Greens, Year after Year

Saving seeds from your own plants is an economical way to enjoy your favorite varieties season after season. And instead of feeling disappointed when your plants bolt, you can see it as an opportunity instead!

A close up horizontal image of bright yellow flowers forming on the top of long stalks pictured on a soft focus background.

Plus, the pretty yellow flowers attract pollinators and beneficial insects to the garden.

Did you let any of your mustard plants flower and produce mature pods? Let us know and share your tips in the comments section below!

And for more information about mustard greens, check out these guides next:

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An avid raised bed vegetable gardener and former “Dirt to Fork” columnist for an alt-weekly newspaper in Knoxville, Tennessee, Rose Kennedy is dedicated to sharing tips that increase yields and minimize work. But she’s also open to garden magic, like the red-veined sorrel that took up residence in several square yards of what used to be her back lawn. She champions all pollinators, even carpenter bees. Her other enthusiasms include newbie gardeners, open-pollinated sunflowers, 15-foot-tall Italian climbing tomatoes, and the arbor her husband repurposed from a bread vendor’s display arch. More importantly, Rose loves a garden’s ability to make a well-kept manicure virtually impossible and revive the spirits, especially in tough times.

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Michelle (@guest_17647)
1 year ago

Can I let my kale, mustard and radish go to seed in the same bed as I’m growing my tomatoes without negative affects?
Zone 7b nice Gardener. TIA!

Briana (@guest_31525)
Reply to  Michelle
10 months ago

Golly, looks like no one has helped you out 😕. If you have a Facebook account, you may be able to find vegetable garden groups for your area. I’ve done that and have found members in the group very helpful.