The spinach is an annual, which willingly cross-fertilizes with all other kinds of spinach, but not with goose-foot and chard. There are several varieties. Spinach flowers are male or female or both.

Sow as usual in spring and remove bad-looking plants. The first plants that begin to bloom, should also be removed. Early blooming spinach is not suitable to reproduce from. Male plants are taller and thinner and all of them should be removed when the blooming is over to give the female plants more space.

Autumn-sown spinach that survives the winter, possibly with some cover, yields ripe seeds earlier.

When the plants have grown yellow-brown, pull them out and hang them up to dry. Some fully ripe seeds could tumble during drying and it is important to put a large cloth beneath the drying plants. The seeds ripen unevenly. Be careful when harvesting. The first, best ripe seeds are loose.

Thresh by pulling the seeds off by hand. Use a flail or threshing mill for larger amounts, but some seeds may get stuck and must be loosened by hand. Clean the seeds from the rubbish by sieving and winnowing.