Seed Saving from Beetroot
Beetroot, leaf beet/perpetual spinach, swiss chard & sugar beet are all members of the same family and will readily cross with one another. Since the flowers are wind pollinated, crossing can take place with any other flowering beet plants within around two miles!
However, most people do not grow beets for seed and their plants will be harvested as food in the first year of growth. Since beets are biennial, (flower in their second year) even if beets are being grown close by, they will be harvested before flowering so not able to cross-pollinate your plants.
Plant beets being grown for seed closely together in a square. At the end of year one, chard and leaf beet can be overwintered in situ. Select a minimum of six to eight plants to leave for seed.
Beetroot can also be overwintered in situ, or can be harvested in autumn, the best plants selected & stored then replanted in spring.
At the end of the second year, when the plants have flowered and set seed, take seed from the central plants in the block; you will find that the amount of ‘contamination’ is minimal providing there aren’t large numbers of other flowering beets right next door.
If you are aiming to keep a variety true to type you need to isolate it, usually by physically covering your seed plants.
To do this, plant at least six plants very close together in a circle, with a wooden stake in the middle. As the seed stalks form, growing up to four feet tall, tie them together, supported by the stake. Then as they develop cover the group of flower heads with either a shiny paper bag that will withstand rain, or a bag made out of agricultural fleece.
Shake the bag from time to time to make sure that pollen is distributed within the bag.
As the large, prickly seeds mature, keep an eye on them, and start to harvest as they turn brown and start to dry out. You can either cut entire seed stalks, or harvest mature seeds by rubbing them into a bucket.
You can watch this video to learn more.
Make sure that the seeds are thoroughly dry before storage, and they should last at least five years.