Week of April 29, 2002
Submitted by Calvin Finch, Ph.D., Manager, Conservation Division, Water Resources & Conservation Department, SAWS, and Horticulturist

SUMMER ANNUALS

The cool weather flowers such as snapdragons, petunias, pansies, and dianthus are at their peak, so it is hard to think about hot weather blooms but, if you want a good display this summer, it is time to plant them.

All the fancy modern petunias look great now, but it is not a good time to plant more. They do not last long in the heat. The first few days of 90-degree temperatures and the petunias will decline quickly. There are a group of petunias, however, that will last as long as zinnias, celosia, or most summer annuals. They are the new “old-fashioned” petunias. Petunias like ‘Kahuna’ and ‘Laura Bush’ have been bred to tolerate heat. The color selection is not great yet, violet is it, but they will grow aggressively and stay covered with blooms all through the summer. Plant the ‘Kahunas’ and ‘Laura Bush’ petunias in full sun for best performance. They also make good plants for hanging baskets.

If you are from the North you remember cockscomb, also called celosia. The old red cockscomb form was common in many summer gardens. Most varieties available in San Antonio have the plume type flower in red, pink, salmon, or yellow, but a few cockscomb from transplants are available and the seed is also available. We generally think of celosia as a full sun plant but I like it as well in a location with sun until early afternoon. It seems to perform longer into the summer if it is spared the full blast of the afternoon sun.

Marigolds are on the market now but I prefer them for the fall. Marigolds are spider mite heaven, they are the first plants to develop populations of the pests, and they readily share the mites with tomatoes and other plants. If you must have marigolds in early summer or you are planting them as a nematode control, get them in now and then be prepared to pull them when the mites appear, or be ready with kelthane (red spider control).

Semperfloren begonias are the best summer blooming plants for the shade. They can even be used in the sun if they are planted in compost-enriched soil and mulched with leaves or grass clippings. The key to good begonia performance in the summer is to plant them early in the spring before mid-May. Once the 95-degree F. temperatures start the begonias will hold on if they were vigorous in the spring. The versatile flowers will perk up again in the fall.

If you live in a neighborhood blessed with deer, zinnias are an excellent choice for summer color. The deer do not seem to like them. The butterflies and hummingbirds do, however. My favorite selection has been ‘Dreamland.” It reaches about 2 feet tall and seems to be more mildew resistant than other selections. Zinnias need full sun to bloom well. Like celosia, expect zinnias to last until July. Replant them for the autumn.

Another deer proof plant is vinca. Vinca, also called periwinkle, is the most drought-tolerant of the summer annuals. It can live and bloom without supplemental irrigation once it is established. Vinca is susceptible to aerial phytophera. To keep the plants from melting down from the fungal disease, plant vinca after May 15 in full sun on a site with good air movement. Mulch the soil and rely on drip irrigation or no irrigation. If you must water over the top, irrigate in the morning so the leaves can dry by evening. Vinca is available in red, white, pink or violet.

            Coleus does not have a showy bloom but its foliage can be spectacular. It varies from a deep burgundy to a light green. Most selections have patterned leaves of two or more colors. Coleus is not a xeriscape plant and is not deer proof but is a good choice to bring color to shady flowerbeds. Planted now it will last all summer.