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Turnips & Oriental Brassicas

Mizuna, pak choi, tatsoi and mibuna are all sub varieties of Brassica rapa - the same family as turnip. This means that although they will cross with each other, or with turnips in flower, they won't cross with broccoli or cauliflowers. Although you can only grow one of these vegetables for seed in any year, you can of course grow any of the others for kitchen use, so long as you don't allow them to flower at the same time as your seed plants.

To grow an oriental brassica or turnip variety for seed, you usually need to over winter the plants. They are naturally biennials, producing their flowers and seeds in their second year of growth. Although spring sown crops may bolt to seed in hot summer weather, this is not ideal for seed-saving, as you may end up accidentally selecting for early bolting in future years. The best solution is to sow your seed crop after midsummer in a greenhouse, where semi-mature plants will overwinter quite happily in all but the coldest parts of Britain. If necessary you can give extra protection in cold weather by putting fleece over plants inside the greenhouse. Select at least 6 of the healthiest and most typical plants to reserve for seed, eating the rest over the winter. In spring, the plants will flower, and then form seedpods. Make sure that there is good insect access to the greenhouse at this point so that the flowers are pollinated.

The seedpods are green at first, but then gradually dry out and turn a pale tan colour. Once most of the pods are dry and brittle, cut the entire stalks of the plant, and lay out on a sheet somewhere undercover with a good airflow to finish drying off. Then rub and crush the pods with your hands to release the seeds, and separate the seeds from the chaff with a coarse sieve. More information on seed drying can be found under our section ‘Seed Cleaning and Drying’ on our website.