So, I recently ordered a salvia divinorum plant, but I think I might have over watered it : the base of the plant is black (althought the rest look's fine for now).

Should I cut above the node, just above where it is darkening, and make a cutting to save it ?

Or, should I wait ? Maybe this is something that happens ? Maybe the plant will recover on it's own.

It doesn't look good.

I suspect you'll need to cut it, but maybe keep an eye on it for a couple days. If it keeps creeping, cut away.

Make sure to give it plenty of air flow. Overwatering usually only turns to that with lack of fresh air exchange, ime.

Unfortunately, I also went through similar issues. Salvia plants do not travel well, I suspect. It'll need humidity for the time being. Enough water few times a week, allowing it to be moist for some days, too. Part sun, at least until it can begin growing some maturity.

Hope it does well.

Symptoms seem like that of root rot

I will wait and see if it keeps on moving up.

Your probably right about it needing more fresh air exchange I will look out for that.

Thanks for your input

How's your plant going?

I found that if that black part is not soft at all but relatively hard (maybe as hard as the rest of the stalk), it may be okay and normal. Some of the plants I've known had their black bit (only refering to the black bit at the base, not other random black parts) hardened more and acquired a wood-like texture and appearance and the plants remained healthy and vibrant.