Pollination: Grain amaranths and leaf amaranths are both mainly wind pollinated, although insect pollination is possible.
Isolation Distances: For commercial production of large amounts of grain, 5 km distance may be necessary for seed purity, but in a home garden situation be sure to plant your amaranth in beds with several rows close together in blocks to encourage cross pollination between plants.(picture Franzi)
To keep the seed strong and seed lines pure I have found planting different cultivars 10 m apart with tall crops in between works well. I’ve never seen any crossing in my garden over ten years of growing two varieties each year. If you find varieties crossing, at this distance you may have to plant yours further apart.
Minimum Numbers: 30-60.
Best Time To Plant for Seed Saving: To achieve a heavy crop of seed the plants must go into the ground, at the same time as your main crop corn. I plant mine in seed trays 3 weeks before that, and prick out as they emerge at 2.5cm diagonal spacings, and then into the ground at 30cm diagonal spacings into Bio intensive beds.
Rogueing: Pull out any plant that does not look true to type before flowering, ie smaller, taller, weaker, different colour, etc.
Support /Protection: We cover our beds with bird netting held up on concrete reinforcing rods bent over to form an upside down U shape, to protect from bird damage.
Harvest: Seed ripens from the bottom of the stem up. It’s easy to tell when to harvest the heads as they change colour from bright and showy to dull, and the seed come sout easily when you rub them in your hand.
Drying: After harvest lay in plastic house on wire shelves especially built high up for drying grains if they have not reached the dry stage before you harvested the seed heads.
Your propagation benches in the greenhouse will do as well, as long as they are not solid wood (the air needs to be able to move through the plants to fully dry the seed in our climate) before threshing and winnowing.
Threshing: Once the heads are dry and crunchy, you can lay them on a sheet or tarpaulin on the concrete or hard ground and dance on the heads, or thrash them with a flail (see diagram 4) or rub them by hand to get the seed out of the heads. The more heads you have, the less you will feel like rubbing them by hand, and the more you’ll find a way to dance/stomp/flail them.
Winnowing: Once the seed has been dislodged it is easy to winnow by tipping from a bucket into a large cut off barrel, another bucket or a screen, a few times, to blow away the rubbish. I then return the seed on a sheet to the greenhouse bench for a few days to finish drying and then store in a barrel or jars until needed in the kitchen.
Seed Life Expectancy: In cool dry dark conditions we find amaranth seed will retain 80% germination for many years, it is regarded as a long lived seed.