Saving your own kohlrabi seeds is one of the most rewarding parts of gardening. Kohlrabi belongs to the Brassica oleracea family, which means it is a biennial plant that produces flowers and seeds in its second year. With a little patience and the right technique, you can harvest hundreds of viable seeds from just a few plants—ensuring future crops, improving resilience in your garden, and preserving varieties perfectly suited to your climate.
Understanding Kohlrabi as a Biennial
- Kohlrabi produces bulbs in its first year, but flowers and sets seed in its second year.
- Plants must survive winter (or be protected) in order to “bolt” and form flower stalks in spring.
- It cross-pollinates easily with other Brassica oleracea types—cabbage, broccoli, kale and cauliflower.
- To save pure seed, ensure no other brassicas of the same species are flowering nearby.
Selecting the Best Plants for Seed
- Choose healthy, strong plants that produced good-sized, uniform bulbs.
- Avoid saving seed from plants that bolted early, split, or grew irregularly.
- Pick 3–6 plants if possible—this maintains genetic diversity.
- If your climate is warm, look for plants that handled heat without stress.
Overwintering Kohlrabi for Seed Production
- Leave bulbs in the ground after harvest time.
- Mulch heavily to protect plants during cold weather.
- Alternatively, harvest bulbs, store over winter, and replant them in early spring.
- In spring, the plants will send up a tall flower stalk—this is normal and expected.
Flowering and Pollination
- Kohlrabi produces clusters of small yellow flowers on tall stems.
- Bees and other insects pollinate the flowers.
- To keep seed pure, avoid flowering brassicas nearby, or use insect-exclusion mesh.
- If cross-pollination doesn’t matter to you, simply let them bloom freely.
When and How to Harvest Kohlrabi Seeds
1. Watch the Seed Pods Mature
- After flowering, plants produce long, thin seed pods called siliques.
- Pods begin green and plump, then turn pale yellow or tan as they dry.
- The seeds inside change from light yellow to dark brown when fully mature.
2. Harvest at the Right Time
- Cut seed stalks when pods are mostly dry but before they shatter.
- Place stalks upside down in a paper bag to finish drying safely.
- Keep bags in a shaded, ventilated area for 1–2 weeks.
3. Extracting the Seeds
- Rub pods between your hands or against a colander to release seeds.
- Blow away chaff or use a gentle fan to separate light debris.
- Only keep seeds that are firm, round and dark brown.
Cleaning, Drying & Storage
- Spread seeds on a plate or tray for several days to remove all moisture.
- Store in a labelled paper envelope or airtight jar.
- Keep in a cool, dry place—ideally in a fridge for long-term storage.
- Properly dried brassica seeds last 4–5 years, sometimes longer.
Common Mistakes When Saving Kohlrabi Seeds
- Letting pods drop seeds before harvest (use paper bags early if windy).
- Saving seed from stressed plants—can pass on undesirable traits.
- Crossing with other brassicas, producing unpredictable offspring.
- Storing seeds while damp, leading to mould or reduced germination.
Improving Seed Quality Over Time
- Save seeds from plants that performed the best in your climate.
- Observe which plants resisted pests naturally.
- Choose strong bulb shape, colour and growth habit.
- After a few seasons, you’ll have a locally adapted kohlrabi strain.
Using Your Saved Seeds
- Sow in autumn, winter or early spring depending on your region.
- Use saved seed for testing germination rates each season.
- Share excess seed with friends or seed-saving groups.
- Plant a “seed plot” each year to refresh your stock.
Next Steps
Once you’ve learnt how to save kohlrabi seeds, you can explore growing, companion planting, or turning your harvest into delicious meals.
👉 Learn how to grow Kohlrabi successfully
👉 Plan a companion-planted Kohlrabi bed
👉 Discover cooking, fermenting and recipe ideas
👉 Find comprehensive information on Kohlrabi