How to Harvest and Store Kale Seeds

In the last few decades, nutrient rich kale has become widely popular as a healthy staple for meals and snacks. And home gardeners have readily embraced it in the veggie patch as well.

This easy-to-grow leafy green thrives in cool temperatures, and a generous selection of cultivars make it a beautiful and delicious addition to the garden.

A vertical image of deep purple kale stems, with dark green leaves and bright yellow flowers. The background fades into soft focus, to the center and bottom of the frame is white and green text.

A member of the Brassica genus, these plants are biennials. They produce leafy growth in the first year, then overwinter in the garden. In their second growing season, they resume growth, flower, then set seed.

With plenty of open pollinated varieties to choose from, reproducing plants true to their parents is easy. And you can begin your own organic, heirloom collection – a wonderful legacy your family will cherish for generations!

Let’s look at the easy steps involved to save and store your kale seeds.

Second Year Growth

Although it’s often grown as an annual, kale requires two years to complete its life cycle.

To collect seeds, you’ll have to let your plants overwinter. This is good news if you’re in USDA Hardiness Zones 7-10, because you’ll also be able to harvest yummy leaves all winter!

A close up of curly kale leaves and stems seen covered in snow, on a snowy background. The dark green of the leaves contrasts with the bright light reflecting on the white frost.

In late autumn, lay down a thick, 4- to 6-inch layer of mulch around the base of plants. Compost, grass clippings, leaf mold, sawdust, and straw are all good materials to use.

In spring, this cold weather brassica is one of the first plants to awaken and quickly yields fresh leaves early in the season. By summer, plants have finished their life cycle and will set buds before sending up tall flower stalks. Pods form shortly after.

Curly kale bushes with long stems of bright yellow flowers, next to a rock, with some river stones to the left of the frame, and the background is stones and vegetation in soft focus.

Leaves can be harvested as long as the plant is viable, but the flavor will suffer once they flower. They’re still suitable for use in stir-fries and soups, but will be tougher and if eaten raw, they may taste bitter.

Gather Flower Stalks

As temperatures rise, each plant sends up tall flower stalks that reach 3 to 5 feet high with large terminal racemes made of small yellow flowers.

A close up of a kale stem with lots of small yellow flowers towards the bottom of the frame, to the top of the stem there are closed buds yet to bloom. The background is soft focus green.

Once the flowers finish, long, thin pods form on the stalks.

And as they fade from green to beige, you need to act quickly to preserve the ripe fruit. Waiting too long can result in dry pods bursting open and dispersing their cache.

A close up of Brassica oleracea branches with developing seed pods. The pods are green and have small droplets of water on them, the background is a bright soft focus green.

Flower stalks can be somewhat brittle, particularly in high winds. If stems begin to flop as they mature, gather a handful together and attach them to a bamboo stake for support to preserve your harvest.

Once the pods have ripened and begun to dry out, cut stalks close to the ground.

Invert the stems with heads and place them in a large paper bag. Tie off the opening with garden twine then hang the bags in a cool, dry location out of the wind.

In areas with high humidity, place only a few stems in each bag to avoid mold.

Once the pods are thoroughly dry, in 10 to 21 days, shake and slap the stems inside the bag to dislodge the seeds.

Winnow Out the Chaff

All varieties produce small, round seeds that are black, gray, or tan colored.

A close up of kale seeds, their colors ranging from very dark brown to very light tan. The texture of each seed is clear, with a slight indentation running across them.

When collecting your own seed, the bits of dried casings and flower stems (or chaff) need to be separated from the seeds by a process known as winnowing.

This can be done using a screen calibrated with holes large enough for them to fall through as you gently shake it. Discard the chaff left on the screen when finished.

Or, on a breezy day, use a mesh strainer or winnowing basket to gently toss seeds up in the air and let the breeze take away the chaff. They need to be tossed high enough for the wind to catch the chaff and disperse it, but not so high as to lose them!

A third option is to dump seeds and chaff onto a large plate and manually separate the two, pushing the chaff aside and saving the seed.

Safe Storage

A single plant can produce hundreds of seeds, and proper storage conditions are required to keep them viable.

Store them in paper envelopes or ceramic or glass jars, then label with the plant name and date.

To the right of the frame is a small white ceramic pot, on its side, with Brassica oleracea seeds spilling out of it onto a wooden surface. Next to it are some tiny microgreens with a small amount of soil on the end of the stems.

Once packaged, they require a cool, dark location that keeps their moisture content stable.

Temperatures of around 50°F with a humidity of 40 percent are ideal – which makes the produce drawer in your refrigerator a sweet spot for storage.

Other good locations include unheated garages, potting sheds, and root cellars. If your unheated areas flirt with temperatures close to freezing, place your seed containers in a small insulated beverage cooler before storing.

When stored properly, they will remain viable for up to four years.

Save a Seed, Sow Some Love

Saving your own open-pollinated seed is smart and economical.

It ensures plants grown from seed will be true to their parent, and you get complete control over their growing environment.

A close up of a healthy Brassica Oleracea plant growing, the small tender leaves in the center and larger, curly leaves around the edges, in bright light.

You’ll never have to buy seedlings again, and you can create your own heirloom lineage of plants – perfect for the self-sustaining or organic gardener.

Plus, you’ll never have that excruciating wait for your local garden shops or direct order companies to be stocked for spring before starting your plants!

Remember to overwinter your kale to collect the seed. And be sure to collect plenty.

Seeds make a great gift fellow gardeners will love, and can be used as tender to barter with at your local seed exchange.

What varieties are you folks saving? Let us know in the comments below.

And be sure to check some of our other guides on this delicious, nutritious green. Here are a few that might interest you:

Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Uncredited photos: Shutterstock.

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About Lorna Kring

A writer, artist, and entrepreneur, Lorna is also a long-time gardener who got hooked on organic and natural gardening methods at an early age. These days, her vegetable garden is smaller to make room for decorative landscapes filled with color, fragrance, art, and hidden treasures. Cultivating and designing the ideal garden spot is one of her favorite activities – especially for gathering with family and friends for good times and good food (straight from the garden, of course)!

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