A question from a fellow grower:
accidentally broke off a main cola on a sour deisel. it is about a month before harvest… outdoors. have it soaking in a solution. is it a lost cause or is it possible to graft it back on the mother plant. if so, how? peace
Grafting expectations are very low, even with someone with experience; not to mention the stress you would be introducing while in flower. You’re better off fixing the break with a clean cut and throwing it in water to root.
It probably won’t fill out much more, but has a better changes of survival. Check out cloning techniques on this.
If it broke off completely; I would try to root it. take a 1 gallon pot and put seed starting mix in it. Get some rooting hormone, and trim stem as you would a clone. cover with rooting powder and stick it into the pot. Water in and do not over water after that. Try to keep medium moist.
If I read your post correctly, you stated this plant was a month old…It can be rooted. Good Luck. Now you may end up with an extra plant.
Trying to graft it or re-attach it to plant…Forget about it! 
OOOOoooooooops! You stated a month before harvest. Just let it go.
Maybe some other member can use my above advice in the future. Sorry