WHEN TO PRUNE FLOWERING SHRUBS
By Douglas F. Welsh, Landscape Horticulturist
If a shrub is grown for its flowers, time the pruning to minimize disruption of blooming. Spring-flowering shrubs bloom on last season's growth and should be pruned soon after they bloom. This allows for vigorous summertime growth and results in plenty of flower buds the following year. [Prune late spring after flowering]
Some examples of shrubs that bloom on last seasons's growth are:
- Cercis canadensis - Redbud
- Chaenomeles japonica - Japanese Quince
- Chionanthus virginicus - Fringe Tree
- Forsythia spp. - all Forsythia species
- Lonicera spp. - Honeysuckle
- Rapheolepis indica - Indian Hawthorn
- Rhododendron spp. - Azaleas & Rhododendrons
- Rosa spp. - Rambling Rose species
- Spiraea spp. - early white Spirea species
- Viburnum spp. - Viburnum species
Some shrubs that bloom after June usually do so from buds which are formed on shoots that grow the same spring. These shrubs should be pruned in late winter to promote vigorous shoot growth in spring. [Prune January-February]
Examples of shrubs that bloom on current season's growth include:
- Abelia X. grandiflora - glossy Abelia
- Buddleia davidii or B. globose - Butterfly Bush
- Hibiscus syriacus - Shrub Althea
- Hydrangea arborescens - Hills of Snow
- Hypericum spp. - Saint-Johns-wort
- Lagerstroemia indica - Crape Myrtle [proper pruning - prevent crape murder http://thedailysouth.southernliving.com/2009/02/24/what-concerns-p/]
- Rosa spp. - Bush Rose [including Knock Outs, etc] [rule of thumb: heavy on Valentine's Day, lighter on Labor Day; see http://www.bhg.com/gardening/flowers/roses/tips-for-pruning-roses/ for tips]
- Vitex agnus-castus - Chaste Tree [we just call it Vitex]
For complete information on pruning shrubs, consult our website: www//aggie.horticulture.tamu.edu