Amaranth definitely attracted the most attention in my garden this summer...at least by people. It towered over us, growing taller than myself and thriving even with little water. Though amaranth is most commonly known for its high protein grain, the primary reason I grow it is for the leaves. They are nutritious, mild tasting, colourful, can be eaten raw or cooked, and make wonderful purple pesto. It does like sun but did fine in part shade as well. Amaranth makes a great companion for lettuce as it provides dappled shade, without making the plants leggy and weak. Having a deep tap root, it does not compete for soil space with plants that have shallow roots, such as lettuce and brassicas.
If you want to harvest the gluten-free grain, wait until the plant matures and either shake the grain into a large paper bag, crush it with your hands or use a comb to facilitate the grain being released. Let it dry (perhaps on very low in the oven) and blow off the chaff with your own breath or with a fan. When harvesting the leaves, we usually eat the smaller leaves raw, chopping them fine and cook the older leaves. One can also make delicious purple pesto. Unlike with basil, I do not recommend pinching off the top. Though it can be done, the stem has a tendency to split this way.
Though the earwigs loved to hide in the upper folded leaves, at least the established plants did not show signs of damage and slugs simply didn't climb that high. What did cause a real issue for the amaranth in my garden was pill bugs. They managed to take down a large plant at the base, after hiding in a nearby row cover. They also completely decimated a dozen seedlings. I was able to save a few tender starts by green mulching around the base so the rolly pollies had something else to munch on. For the most part, once established and if the stem is given room, the insects simply don't like the amaranth like we do.
If you are growing amaranth in fertile loose soil just make sure to stake your plant somehow!
I grew 2 types of amaranth this summer and both were fabulous, though Red Garnet Amaranth gave more grain and Hu Hsien did really well in pots. The history and cultural significance of this plant is worth looking into. It has been revered, burned and banned and reclaimed.