Blooms may last longer in climates that are cooler than ours, but cooler climates do not have the potential for two spectacular bloom periods each year like we do in South Texas. We expect our flowering perennials to bloom well in the spring but we overlook the best possible season for bloom—fall. Plants do not flower to make us happy; they are flowering to produce seed and complete the reproductive stage of their life cycle. If the old flower stalks are cut off and not allowed to mature seeds, the plant will attempt to make more seeds. Then we get to enjoy another bloom cycle.
Hot weather greatly shortens the life and beauty of blooms. During the spring bloom season, Texas weather makes the transition from winter to summer—Texas temperatures rapidly change from frosty to scorchy. The fall weather conditions, in comparison, are ideal for blooms. Usually the extremely hot weather ends in September and the cooler temperatures, especially at night, signal that the South Central Texas “second spring” has begun. These cooler temperatures stimulate plant growth and intensify the color and duration of the blooms. Many people do not prepare their plants for this second spring so they miss really the most spectacular bloom period.
August is the time to act. Shrubs that bloom after June usually do so from buds that are formed on shoots that grow the same year. These shrubs should be pruned in late winter to promote vigorous shoot-growth in spring. Examples of shrubs that bloom on current season’s growth include: Vitex, Butterfly Bush, and Hibiscus. Fall-blooming perennials, such as Salvia , Mexican Marigold Mint and Chrysanthemum should have been pruned periodically during the summer to keep them compact–if you didn’t do that pruning, cut them back by one-third as soon as possible. Perennial or Summer Phlox should be cut to the ground and allowed to resprout with new stems.
By Dr Jerry Parsons