Saturday, April 27 2002
Submitted by Calvin Finch, Ph.D., Manager, Conservation Division, Water Resources & Conservation Department, SAWS, and Horticulturist

SUMMER BLOOMS

We went from winter to summer without much of a transition for spring. If you want summer color, it is important to do some planting now.

Semperfloren begonias are top bedding plants for shade in South Texas. They will even work in the sun if they are planted now. They will grow strong for 8 or 10 weeks and then “hunker down” for the hottest part of the summer. If they are well established in a compost-enriched bed, mulched, and watered with drip irrigation you can expect them to look presentable until autumn when they perk up in the cool weather. There are a number of choices of semperflorens; I have also had good luck with the whiskey and vodka selections. Flowers are carmine or pink and leaves are light green or red-green. All of the begonias in this group have waxy leaves. They are drought tolerant.

Moss roses (portulaca) and purslane are a lot alike. They grow low (6 inches), tolerate heat and drought, like full sun, and offer a large range of flower colors. Red, orange, white, pink, yellow, and bicolors are available. The newer selections expand the daily bloom period beyond banker’s hours. One complaint on moss rose and purslane is that they only bloom during the day, every day all summer, but they are not early risers or late bloomers. Both plants are good choices for hanging baskets or other containers. Moss roses will reseed in locations where the seeds can reach the soil (no mulch) and remain in full sun.

Zinnias are outstanding summer bloomers. ‘Dreamland’ is the selection I have had the best luck with because it seems to resist mildew for the longest period. The hybrids like ‘Dreamland’ are full, uniform, and colorful (red, white, yellow, lavender, orange), planted now as transplants they will perform well until July. In later July you can compost the old plants and replant fresh transplants for the fall. Another strategy to consider is to let a few of your flowers at the end mature and drop their seed. The naturalized zinnias that follow do not offer the uniformity or color variation that the hybrid transplants provide, but they produce lots of flowers until cold weather. All zinnias are attractive to butterflies but the naturalized versions seem to offer more nectar. They are especially attractive to butterflies. Use zinnias in full sun. They make excellent cut flowers and seem to be deer proof. If you deadhead zinnias (remove spent flowers) they bloom longer and more attractively.

Vinca (periwinkle) is an annual flower that, like moss rose, qualifies as a xeriscape plant. It requires full sun to prosper but once established tolerates droughts just as well as lantanas, salvias, or the other well-adapted perennials. Plants in full sun provide quarter-size (coin) flowers in lavender, white, and red-pink. There are many bicolors. Some selections are 8 to 10 inches tall but most are in the 18 to 24 inch category. Deer do not eat periwinkle. They sound perfect, don’t they? And, in fact, for many years vinca was the most popular annual flower in the U.S. In the last few decades, however, aerial phytophera, a fungal disease, has found vinca.

Recognize aerial phytophera by a meltdown of the vinca plant. The disease is everywhere and has forced us to only plant vinca in conditions where the plant can survive. Plant vinca after the middle of May when relative humidity has dropped. Only irrigate by drip irrigation or, if you must irrigate overhead, do so in the morning so the moisture on the foliage dries before nightfall. Mulch under vinca so the soil does not splash on the foliage. The fungal spores survive in the soil. Once on the plant they start the disease cycle.

Vince is still a good annual flower for beds in full sun with plenty of air movement. Get it established and it will bloom with only one watering per month.