Q.Mandevilla
I purchased a mandevilla (red) and it was split right down the middle, exposing the woody stem. Can I just use some string to keep it together and plant it? Or should I completely split it and plant them in individual pots?
I would first see if the place in which you bought it would take it back, as most should. If not, there may be little you can do. While you could string them together, there is no guarantee that it will work. Split stems will also be an invitation to pests or disease, so just to be safe I would treat with neem oil. Unless you could get two individual plants with roots, dividing it won't do much good either. In the meantime, you could just keep a watch on it. If one of the halves looks weaker or more unhealthy than the other, you could simply remove it.