Water it well, not soaking wet, but damp. Make sure to cut out well away from the plant, a good 5 inchs all around the the plant at least. Go deep to get all the roots. Then try to put it in a pot big enough to leave it in for the rest of the summer. YOu can re-plant the dahlia tuber later.. Yes, this can be done. Just be gentle. Bertram Vancouver Canada.