Well, yes, depends.... ;o)) That is not what I intended to do when temporarily moving a mophead to protect it from roof work when, whoops, all of the sudden I had two mopheads instead of just one.... Those shrubs are not really geared for splitting them like that but many people do so successfully. If you want to play it safe, first propagate from cuttings and then try dividing... just in case things go badly.

I did the same thing last year with Pistachio to save it from my original spot (hot and dry). Ended up with one big pot of it and 3 smaller pots of much smaller plants. Maybe one year I will find a good spot in the yard to plant it.

I have been successful in dividing large mature hydrangeas. As long as there are roots, it should work. The problem with dividing rather than using cuttings is the shape of the new shrub and the old branches attached to the root ball may not be very attractive and the time to get it back to a beautiful plant may be several years.. It is one way to propagate a mature plant immediately. No need to wait for the cutting to root, branch out in the spring and then grow at a rate that will seem slow to a new gardener. It also works great if you have to move a mature plant- for temporary reasons or if you are actually moving to a new home. Digging the mature root ball from the ground is a big chore and takes a lot of muscle. All of the old soil should be washed off the root ball and then planted in the same soil it where it will be situated. If this has to be done in hot weather, I would suggest plunging it into a bucket of water for at least 12 hours before planting. This give the shrub a good hydration before being replanted in the container or new site. Due to circumstances beyond our control, one mature plant had to spend almost one month in the bucket, in the shade, and finally when planted - in several pieces - did just fine.