Turnips are cool-weather vegetables and offer a variety of nutritional benefits in the root and the greens. Dating to the prehistoric era, turnips (Brassica campestris) have provided a rich source of vitamins A, C and K, calcium and iron. Turnips are a delicious addition to soups and stews and make an excellent side dish when boiled or sautéed. In addition to the root, turnip greens are a staple in southern dishes and packed with nutrients. When grown from seed, harvest occurs from 45 to 75 days, depending on the variety grown.
Grow at least 20 turnip plants, when saving seeds, to prevent mutations in future cultivars caused by inbreeding.
Allow turnip plants to develop flowers, and avoid harvesting greens from seed plants, as this can weaken the viability of the seeds.
Pull the entire plant when the seed pods dry to a light brown shade. Discard any plants with wilted or discolored greens to prevent propagation of diseased specimens.
Lay turnip plants out on a bed sheet, in a dry, breezy location, to finish drying.
Remove seed pods from each plant, discarding those that are still green.
Place seed pods in a cloth bag, and pound the pods with a mallet to release the seeds.
Winnow away chaff and seed pods by pouring the seeds into a bowl or bucket lined with a towel, holding the bag at least 6 to 12 inches above. Do this outdoors, or in front of a fan on a low setting, so that the chaff and pods will blow away from the container, leaving clean seed.
Lay the seeds out on a screen or baking sheet to dry for one to three days, then store them in airtight plastic bags or glass jars with lids.