Margaret commented on The Survival Gardener community:
Here’s an amaranth story: Two years ago I bought some amaranth seedlings to see how they would grow. They grew about two feet, were covered in bug bites, and ended up in the compost pile. About a month ago I added a generous amount of compost from that bin to my garden beds. See here.
That’s epic.
Amaranth really loves disturbed soils and grows very vigorously when native.

It’s also interesting that seeds have come out of the compost pile – in my experience, seeds often survive composting, even when you try to compost the “right way” by composting at high temperatures – seeds are good at surviving and they love compost.
Last year, purple amaranth grew and left seeds in the garden, potting soil, and nurseries, so this year it’s blooming everywhere, but that’s OK, because it’s pretty, and much nicer than its prickly pigweed cousin.
Seeing my Margaret Amaranth growing out of control makes me want to sow seeds all over my food forest and see what happens next spring. Daisy is already selling purple seeds in the seed store. I also have some Golden Giants that I think would be fun to sow there.