Looks like okra, to me!

It's been a while since I've grown okra but the leaves look right, the plant should be one main tall stalk as it matures.

Okra at that size it should be flowering and fruiting already, unless perhaps it's not hot enough

Okra is in the mallow family, but okra has bigger, less round leaves, and it grows tall instead of flat. This isn't okra, though. It looks like mallow (the leaves don't look the same shape as the Malva neglecta found where I live, but maybe it's another species or has different traits in your area). Okra has bigger, showier flowers (yellow flowers with black). I see white flowers in the picture. You can see the fruits on this, and they look like little, flat, round mallow fruits.

Agree with Mokinu's comments, it is a mallow. A similar wild mallow has been in every garden I've ever had, from NorCal to Wisconsin. There is even some coming up in my okra rows, where the family resemblance is quite visible. I allow Malva sylvestris to self-seed in my garden, it has nearly identical leaves to common mallow, but much larger purple flowers. It is an outstanding bee plant.

Mallows are not really terrible as weeds, and will even function as a trap crop for Japanese beetles... but I recommend pulling that one soon, because some of the seed pods are nearly ripe. The seeds are very long lived in the soil, let them go to seed once & you'll be fighting them for years.

Thank you all so much, most informative. What a bummer... I've removed it, but the roots has gotten huge already!

If you are having a problem pulling it out, I suggest you grab the main stem and twist it around and around until the smaller roots snap off and then try pulling out the main plant. I do this with zebrina hollyhock (also a malva) which is almost impossible to yank out when fully mature.

Malva parviflora.