I have three questions. The first is about a very large crape myrtle, in a very small space. The more I trim it, the bigger it gets. I cannot move it, and the root system is everywhere. Do I cut the entire lot back down each spring, or do I stop pruning altogether? Will blooms appear on wood from this year, or does it need new wood?

Also, my lilacs aren't doing anything, year after year. They just sit there — they don't die, but they don't bloom. Should they bloom on old or new growth?

Finally, my butterfly bushes bloom fine all summer. Should I cut them back this fall, or next spring?



Crape myrtles flower on new growth. To get the best size control, they can be cut back to stubs just a few inches from ground level every spring, and they will still bloom as long as they receive ample sunlight.

Lilacs bloom on old wood. If pruning is necessary, it should be done right after they finish flowering in spring. Pruning anytime after midsummer will limit or eliminate flowers the following year. Lilacs bloom best in full sun. The more shade, the fewer the blooms. If shading is a factor, transplant it to a sunny site.

Lilacs are also subject to cold weather damage. Single digit or colder temperatures during winter, and late spring frosts that arrive after they break dormancy will reduce or eliminate flowers for that year. Young lilacs often experience a juvenile period where they are too immature to flower. I have heard of some varieties of lilac taking as much as seven to 10 years before they mature and start to flower reliably. Patience is the key to curing juvenility.

Butterfly bushes are like crape myrtles in that they also flower on new growth. Don't prune in fall. If we have severe cold in winter, you might lose your plant. Wait until spring and prune butterfly bush as its buds begin to swell. Cut it back to a low framework of branches about 6 to 8 inches from the soil line. Remove all but two buds of the previous year's growth from each stem.


Write to Chip Tynan at chip.tynan@mobot.org or Horticultural Answer Service, Department PD, P.O. Box 299, St. Louis, Mo. 63166. Check his blog at mobot.org/gardeninghelp/hilight.asp