Radish White Icicle (Raphanus sativus)

Fruiting branches can be cut as they mature or all at once, when approximately two-thirds of the planting is seed mature. Although losing seeds to shattering is not a concern, seed quality can decrease if pods are left in the field for too long after maturity. After they are cut, the mature seed stalks should continue to dry on row cover or landscape fabric in a sheltered location. Threshing is easiest when pods are completely dry, usually after one to five days of drying. On a small scale, plants can be threshed by placing the harvested material on a trap or in a large container and treading upon it until the siliques break apart. Radish pods may not release their seeds easily even when broken open, and it may be necessary to crush fruits completely during the threshing process. When stored under cool, dry conditions, radish seeds can be expected to remain viable for six years.
-Information from Seed Savers