Spinach is a frequent ingredient in my recipes, but rarely the only one. I usually combine it with various kinds of lettuce and other green leafy vegetables.
Sadly enough, spinach is nearly impossible to grow here in the NM desert. As soon as it warms up enough for the seeds to germinate, it gets so hot right away that the little plants always bolted on me to go to seed.
Luckily enough, we have an excellent substitute here in the desert, and the best thing of it is that wild amaranth is a weed that flourishes in the summer months. If there have been some rains, it can cover vast areas. The tender young leaves can be processed exactly like spinach leaves. It's a bit more work because the leaves are smaller, but hey, it's free. The final product looks and tastes the same as spinach. At least I could not tell the difference.
Another good alternative is the subtropical chaya or spinach tree. Unfortunately, that tree is not winter-hardy, so I need to keep it in buckets and bring indoors for the winter. See Cream of Chaya Soup.
Many other leafy vegetables can be prepared in the same way: beet greens, cabbage leaves, carrot greens, chards, lettuce, turnip greens, mustard leaves, radish greens, etc. but those all taste very different than amaranth and spinach.
Green amaranth is by far the most prolific growing weed around here in Southern New Mexico. It needs some rain to get started, but with enough moisture these plants can be 7 ft. tall by August and can cover large areas without any effort at all on your part. When it’s dry, they just stay smaller.
Hispanic people call this plant 'quelites' or 'espinacas' = spinach, which tells you right away what to do with them. These weeds are a perfect summer substitute for spinach. It grows abundantly at a time that you can't grow any spinach here at all. I call it a perfect substitute because I don't think that I could differentiate between the two by looks and taste alone.
I used to have a vegetable garden outside the wall surrounding the house for 3 years (2013 to 2015.) Every fallow patch in that garden just teemed with green amaranth seedlings, so much that in 2014 I decided to keep an experimental patch to harvest the leaves. This was the result.
Pic2: amaranth plants in the desert summer