If I cut a branch off of my rhodo and put it into water, will it root and become a new plant, or is there a special trick to this? Since I'm going to be pruning my Rhodos this year, I might as well take advantage and grow some new ones with the branches I cut off, if that's possible.
Rhododendrons can be rooted from cuttings; last year's growth only, terminal removed, rooting hormone applied, and cuttings put on bottom heat, under mist or in a poly tent to keep humidity high. Some varieties root easily, some do not; cuttings from young plants tend to root more easily than from old plants. If you want to try a few at home, when you prune, take cuttings from that last year's growth (not the whole branch), dip it in rooting hormone, stick the cutting in damp, coarse sand in a pot, put a vented plastic bag over it and put it in a shady location. Keep it moist but not wet; you may get good rooting. Another method for older plants is to layer- stake a limber branch to the ground so young tissue is in ground contact; wait a year, then cut the branch and move- it should have roots. Rooting hormone will also help here.
I've successfully started a couple of rhodo cuttings by just inserting a cutting of fairly new growth into soil, no hormone, no bottom heat, no cover... may just have been easy species or just the right time of year. Bottom line: nothing to lose by trying!
I have been experimenting (yea never ending) with Rhodo cuttings taken at different times of the year and in different conditions etc etc. Now I haven't had much success except with current year's growth taken in fall and put in cold frames. The wood of the cutting must be sufficiently hardened else it just rots ... and if too hardened (woody) then they have a hard time forming roots ... and IMO fall has another advantage in being cool -- I feel this is a key factor!