It is an Orange!
Not a weed. A wee teeny orange tree.
It’s the leaves. The leaves have grown out and given it away as an actual orange tree of some kind. Since I don’t know which part of the seed it sprouted from there’s no telling if it’s identical to one parent or a cross between the seed bearing parent and the pollen producing parent. I could guess, but it would be just that– a guess.
The weather looked like it was going to clear up so my little citrusy babe has spent his first whole day and night out of doors in anticipation of the great glowing orb’s return. He doesn’t look too distraught at the change in light and temperature, although I can honestly say that my desk looks very sad without a wee orange tree on it.

From tiny seeds and acorns do mighty trees grow. Give it another 7 years or so and harvest time. Or not