I did find a picture of a green stem malabar spinach and it does look like that plant.

My malabar spinach has heart shaped leaves. That's not what I see here. But mine is red-stem (basella rubra). Maybe different? This time of year, my malabar spinach is covered in flowers and berries that turn deep purple. I think that should be the case with both varieties. Those berries drop, and the stuff is somewhat invasive as a result. The stuff thrives in hot weather, and slows down considerably in cooler weather. Completely frost-intolerant.

I looked at a lot of photos and there is some variations in leaf shape with some having more of a heart shaped base than others. It did seem like the 'rubra' displays this heart shaped variation more often. I would think the plant should have already bloomed and produced berries by now.

If the leaves have mucilaginous texture and taste rather bland than it most likely is a Malabar Spinach.

My malabar spinach certainly doesn't taste bland, especially compared to other greens. To me, it has a slightly citrussy flavor. Vastly more flavor than most lettuces. The stems are decidedly mucilaginous. The leaves, not so much.

But if it's fall, and it doesn't have flowers and berries, I don't think it can be malabar spinach. The stuff spends a huge amount of effort producing berries. Every year, I have a 4-foot trellis that is overflowing with malabar spinach, and there are *thousands* of berries on it this time of year.