Penta is the common name for a group of upright evergreen shrubs or tall perennials grown mainly for their decorative properties. As is the case with practically every other shrub or tree, pruning is of utmost importance to guaranteeing the health and longevity of your pentas.
Importance of Pruning
Pruning serves a variety of purposes for healthy penta growth. Two common causes of diseases in trees and shrubs is improper air circulation and diminished sunlight exposure, both of which can be resolved by pruning. Pruning can also "train" the shrub to grow in a specific shape and size and can control the spread of diseases or mold and fungal infections that may have taken hold in parts of your pentas. Finally, "maintenance" pruning your pentas can result in healthier and longer blooming periods.
When to Prune
Leonard Perry, of the University of Vermont, recommends only pruning to shape -- in other words, pruning anytime your pentas grow outside of their desired shape or size, which can essentially be done at any time of year. Texas A&M University horticulturists recommend a regular pruning in spring to promote "branching" and "more abundant and better quality flower stems."
How to Prune
Pruning technique depends somewhat on what you are trying to achieve with pruning. To control the spread of disease and fungus, simply prune away diseased parts of the penta and discard immediately. To prune to shape, prune away any branches of other parts of the plant that grow outside of the size or shape that you desire for your pentas. To promote healthy flowering during blooming season, pinch or cut off ("deadhead," as some gardeners refer to the technique) spent flower heads so new, healthy flower heads can grow in their place next season.
Other Pruning Tips
These are generalized guidelines for all pentas, but the prevalence of hybrid varieties and numerous cultivars of pentas means that the type of penta you grow may require more a more customized pruning technique and schedule. Upon purchasing the penta, confer with the gardening store salesperson as to the best pruning techniques for that specific cultivar or, if your pentas are already planted, consult a local university extension service as to the best time and technique for pruning your pentas.