I prune my Myrtles back the end of February. I cut the tall thin branches making certain to remove any dead, damaged, or diseased material first. I use bypass pruners for a sharp clean cut (my favorite brand is Felco, made in Switzerland). I do not cut the branches back every year at the same place. When landscapers and homeowners hack their trees back every single year at the same location, the tree produces an unsightly knot. The issue is that many yards have the wrong kind of Crepe Myrtle planted. Some varieties grow as tall as 30 feet tall. Not good if they are planted right next to your house. Rather than “murder” the tree every year, make certain that you plant a smaller variety and there are many dwarf varieties coming out each year.
It is truly the old adage of making sure you have the right plant in the right place. Down here landscapers are notorious for planting shrubs that are too large for a foundation planting right next to the house. By the way, my Viburnum odoratissimum are gone! I am looking at Florida anise as a replacement
(Illicium floridatum). They like shade and grow slowly at to a correct height depending upon the variety. Hopefully no more whitefly.
It does amaze me to see how people prune shrubs. As mentioned before, power tools are not the way to go. Mow and Blow landscapers just chop and slash away with no regard for when the plant can and should be pruned. I visited a yard last week where there was a large flat topped hedge – it was really scalped. On closer examination, they were Azaleas. They will not bloom this year because the landscaper sheared off all of the buds for this spring. You should prune most flowering shrub after they bloom and no later than July 4th. You do not wish to cut off next year’s flower buds.
You should also prune down here from the inside out, opening up the shrub to air. If you look closely at a massacred shrub, you will see quite a bit of dead material inside the mound of the shrub. If you let that go, you will soon have a shrub with green on the outside and brown on the inside. Ugh. Opening the shrub up also helps to prevent disease. With pruning, always cut out the dead branches first as well as any that are crossing and rubbing against each other. Look for cracked and open branches and discard those as well.
Pruning correctly can help make a beautiful healthy floral display on flowering shrubs and healthy renewed foliage on shrubs not known for their flowers such as Podocarpus, Boxwood, and Ligustrum.