I have professed my love for Orach (also known as Mountain Spinach) before, but I truly am smitten with it. For me, it just fits with my personal kitchen-gardening model. However, there are attributes that might make it unsuitable for everyone’s garden. Most importantly, it self-seeds profusely. For me, this is a huge win, because it is the first thing to pop up in the spring and provides us with bowls of effortless salad in the early weeks when we are still waiting on the lettuces and other spring greens. Because I grow a fuscia/burgundy, and lime-green mix (“Caramel Apple Mix” from Floret), I find it very easy to identify the seedlings in my beds. I plant around them and let them grow. Then I snip them for salads and they are done. They aren’t “weedy” in the sense that they don’t grow back once you snip them at ground level (like, say, dandelions). Taste-wise, I find orach very similar to spinach, though with less oxalic acid (which gives it that distinct mouthfeel) and a slightly saltier taste. By early June, I have harvested all the young orach plants (spare a few that happened to self-seed in ideal locations; those I allow to grow into tall cut flowers. They form spectacular tall seed heads which I love to use in arrangements. They also make a catchy tall border/background flower. I grow them amongst the sunflowers on my fence line (sometimes, by transplanting them there) and I always get questions about them from passersby.
I no longer seed orach (I just wait for it to come up, and transplant as needed), but you could sow it in the fall, early spring, or the summer if you wish (though I wouldn’t do that). It requires no special care. If you don’t want the plants to self-seed then you should snip all the seed heads and use them in arrangements (but if you compost them, know you will find volunteer orach everywhere in following years, which is OK by me).