Posted: 05/06/2012 at 16:24
If you leave it unpruned it will develop stems that are woody, of which have no foliage or blooms. Not nice to look at, IMO.
Group 3 - should be pruned back severely every year in late winter, when they are completely dormant, to about 12 - 14 inches. Leave at least two pairs of buds on each stem of the plant. This group are very fast growers and usually reach they full height before each summer.