I tried my hand at growing New Zealand Spinach this year. I sowed several seeds and they all came up, but a few of them do not look like the others! I don't want to accidentally eat something I shouldn't, so can someone identify if this is a weed or just a taller spinach plant? The leaves also have a sandy underside.
Congratulations, the taller plants you have are Lambsquarter plants. Considered a weed by everyone I've ever met and it sets up to 75,000 seeds per plant. I suggest killing it with extreme prejudice.
From comments it appears that Lambsquarter is in fact edible and grown by at least a few people as food. It is a fast growing plant, in garden soil it will likely top out over 5 feet tall. If you feel like keeping it around I would at least consider repositioning it, because it will have no problem shading out your spinach plants. And for the sake of next years garden, don't let it go to seed.
