Q • I have a rose of Sharon bush that is about 10 feet tall. It has been in full bloom all summer. I need information on how to care for it, such as trimming it and when?
A • The rose of Sharon (Hibiscus syriacus) flowers best in full sun or light shade in a site with a moist, well-drained soil that is high in organic matter.
Pruning is best done in spring before new growth occurs. Young plants can be cut back hard after the first year to encourage branching at the base. They flower on new wood, so how far back you cut on an annual basis is a matter of personal choice with respect to the amount of space available for it to grow.
Plants can also be pruned lightly during the growing season to restrict overly vigorous growth, though pruning at that time may remove buds and reduce potential flowering. Left unpruned, rose of Sharon produces a mature shrub in the 8- to 12-foot tall by 6- to 10-foot width range. Dead wood can be removed at any time.
Write to Chip Tynan of the Missouri Botanical Garden at email@example.com or Horticultural Answer Service, 4344 Shaw Boulevard, St. Louis, 63110.