Plant Answers

Weekly Express-News Article
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
Saturday, August 11, 2007

“The Heat Lovers, Where Are They?”

We have not had a typical South Texas summer, what with near record rainfall amounts and very cool temperatures, but it is interesting to take note of what is blooming in our landscapes in this atypical summer.

Crape myrtles were slow to begin blooming this year but they sure have made up for it in recent weeks. In a previous article, we discussed powdery mildew and sooty mold. Other factors that affect plant health and bloom are lack of sun and poor drainage. If your crape myrtles have been overgrown by shade trees or even shrubs for the smaller selection, you can increase bloom by opening them up to more light. Crape myrtles in shrub borders become covered with vines and lose leaves. This year with all the rain, coral vine, morning glory, green briar, cat’s claw and other aggressive vines are overrunning some landscapes. They shade out the crape myrtle leaves, the leaves drop and there is less bloom.

In a few cases, the soggy soils have caused root injury in plants that are planted in low or poorly drained areas. The symptom in less severe cases is small reddish leaves. The instinctive reaction is to fertilize but that is not a good way to address the problem. The salty fertilizers just stress the injured roots further. An established plant will probably recover on its own. For crape myrtles planted in the last three years you may have to move them if you are going to have a healthy plant. Crape myrtles are drought tolerant and require well drained soil to prosper. If they were planted in a low spot during the two years of drought, soggy soil was not a problem. Now it is and will be in the future.

The poincianas have not liked this wet cool weather much at all. The glow-in-the-dark orange/red/yellow blooms are just becoming noticeable in area neighborhoods. Pull off any vines that have overgrown them. If the sunny warm weather persists through September, they should still make a show and provide nectar for hummingbirds and butterflies.

Vincas are usually the mainstay of summer flower beds in South Texas. This year has not been good for the drought tolerant, sun loving species. They are susceptible to the disease aerial phytophera that results when the foliage stays wet due to rain, humidity, or overhead sprinkling. Many beds of vincas planted in May or June succumbed to the phytophera by disintegrating into a pile of mush. The good news is that it looks like the constant rains have ended and vincas should survive and bloom until November.

Chaste tree (vitex) has bloomed well but you may not notice the blooms this year. The foliage has been growing at the same time and the flowers are partially hidden within the new growth. The hummingbirds and butterflies have been able to find the blooms and they should be more visible this fall.

Texas sage (ceniza) has been invisible in the six weeks of rain. It performs best in dry periods with infrequent rains. Newly planted ceniza is especially susceptible to root damage due to soggy soil. If your ceniza is planted in a low spot it may experience a leaf drop. It does not need fertilizer and in fact, an application of salty fertilizer will add to the problem. Let them recover on their own.

Lantanas have also responded to the heavy rains with a flush of growth at the expense of bloom visibility. They should make a great show this autumn.

Esperanza is also taking advantage of the rain and mild temperatures to grow foliage. The plants are lush and full. Somewhere within the thick growth are the blooms. Like lantana and chaste tree, expect a great bloom period this fall I we can have some normal dry, sunny weather.

Both old fashioned and modern roses often take a break from blooming in July and August. This year they have had weather that could have supported blooms all summer but foliage disease pressure has been so strong that most varieties have lost foliage. If the leaf fungus did not reduce bloom, the heavy rains took a toll on the buds and flowers.

This autumn could be spectacular for all roses if it dries out. Fertilize your roses with one cup of slow release lawn fertilizer per plant and begin your spray program.

Organic gardeners have a new tool in the arsenal to protect roses from insects, Spinosad. Neem Oil and sulphur products are organic controls for fungus. Acephate and Funginex are the usual manufactured sprays for controlling pests on roses. Old fashioned roses and the tough modern roses like Belinda’s Dream and Knockout do not require a spray program most years.