Grain amaranths and leaf amaranths are both mainly wind pollinated although insect pollination is possible.

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 and to keep the seed strong. Plant different cultivars 10 meters apart with tall crops in between.

Ideally suited to Bio intensive mini farming where harvests of 7kg/10 sq. metres can be achieved, the minimum isolation between leaf varieties is 500 ft, and 2 miles between grain varieties. Grow 16 plants minimum, preferably 32 or ideally 64 to keep genetic strength. 

For commercial production of large amounts of grain, 5kms distance may be necessary for seed purity.

I’ve never seen any crossing in my garden over ten years of growing two varieties each year.

As we collect these seeds and we listen, we become aware of the part that the ancestors play in getting them to us. Then we have to be aware that we are the ancestors of the next stage. .... What we’re setting up right now is our role as ancestors for our children and those children five hundred years on down the line for whom we will be these distant little voices in the seeds.