My amaranth reseeds and will grow quickly. We are in the same zone 9a. Go ahead and try it.
Which amaranth do you have?

I ordered from Baker Creek: Green Calaloo Amaranth.
Will plant some today. Are yours tasty in the summer in 9a? I didn't find Malabar Spinach good to eat raw in our hot summers. I am excited to give this plant a try. I wish I had ordered a more colorful variety, as an afterthought, but that is what I get for being impulsive.

Hi there, I do grow Callaloo, which is Amaranthus dubius, as a veggie since last year. Before just used the store bought. They love the heat and full sun and do grow very fast. I don't think they are 120 days to mature at all. I don't harvest them too small, since I don't like the taste when cooked to young. For me they are just right around 3 feet. Not too soft stalks and not too hard either. The will regrow out of the main stalk. I strip them first to remove the stringy outside skin, then leave in a lot of salt water for 10 min and rinse very well. Fry an onion soft, then add cut up callaloo, salt and 1 minced gove of garlic, a bit water and steam until soft. Be careful not to overcook.

I have only grown amaranth for seed. But after seeing this post I may now try the leaves as well. I found this info while looking for seed sources

"Amaranth Edible Red Leaf: FOLIAGE: You can start harvesting leaves when plant is greater than 4" tall; harvested leaves will be replaced with new foliage. You can also wait until plant is mature, between 7 and 9 weeks, and harvest the whole plant; the iron content of the plant doubles between the 7th and 9th week. GRAIN : Wait until seeds are mature and dry. Pull up plant and hang upside down in a warm, dry place; when completely dry, shake seed heads into paper bag. Seeds should be stored in an airtight container."

subtrop ~ Did you get your seeds from Baker Creek?

No, I purchased the callaloo (sold in bunches for cooking0 in the store and set some aside for rooting. That worked and I let those plants go to seed. Keep in mind that callalo produces oxalic acid in the leaves and shouldn't be fertilized with a high nitrogen fert because they'll put that in the leaves and make extra oxalic acid as well.

subtrop ~ Your calaloo patch looks really nice. I would have loved to have a patch of that in my garden this summer too. I've tried to grow the calaloo from Baker Creek several times but they go to seed when the plants are still very small. As for fertilizer, your plants look well fed, so if you aren't using a high nitrogen fertilizer, what are you using?

Christine