Q • I have old boxwood, burning bushes, yew and holly that have not been trimmed in two years. Can I still trim these shrubs now? Or should I wait until fall or next year? I know if I trim back the burning bushes now I may not have much color in fall.
A • You should do light pruning only this late in the growing season — just to even out any flyaway shoots. For heavy pruning of boxwood and yews, wait until after the last spring frost is past (approximately April 15, for the St. Louis area). Heavy pruning of burning bush euonymus should be done in late winter while the shrub is still dormant, before new growth occurs. Many gardeners wait until December to prune holly so they can repurpose their trimmings in holiday season decorations.
Write to Chip Tynan of the Missouri Botanical Garden at email@example.com or Horticultural Answer Service, 4344 Shaw Boulevard, St. Louis, 63110.