Weekly Express-News Article
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
Saturday, April 26, 2008
“Annual Color for Summer”

            In the annual flower garden the snapdragons look great, but within a few weeks they will begin to decline with the heat.  Other cool weather flowers like cyclamen, primula, pansies, stocks, and calendula already look pretty sad.  It is time to consider replacing the cool weather annuals with hot weather flowers.

             There are two cool weather flowers, however, that are exceptions; dianthus and petunias.  If you skin the dianthus with your string mower, they will reset blooms and look good for another two months.  Petunias, especially varieties like Wave, VIP, and Laura Bush will tolerate considerable warm weather and may survive the summer.

             Among the best summer blooming annuals are zinnias, begonias, moss roses, and vincas.

             Most nurseries in our area seem to offer Dreamland zinnia transplants.  Another option is to grow one of the many available varieties by seed.  Dreamland is popular because the colors are strong (yellow, red, pink, lavender and white), the stature is compact and they resist powdery mildew for a longer period.  For best blooms you probably will have to plant one batch now and then replace them in four months.  Plant zinnias in full sun.  They are not xeriscape plants, keep them well watered. 

             Semperfloren begonias are surprisingly drought-resistant.  Get them established now and they will even do well in sunny locations if you have good soil.  They do best in partial shade, however.  Begonias will often provide blooms every day through summer and winter over two or three years if the winter is not too cold.  Begonias have pink, red, or white blooms above lush light green, dark green, or red green foliage.  They grow to about 12 inches tall.

             Moss roses and the similar plant, purslane, grow low (four inches tall), and also have drought-tolerance.  Grow moss roses in beds, containers or hanging baskets in full sun.  Moss roses have strong pastel colors.  They are available in pink, white, yellow, red, and orange.

             Vincas used to be the most popular annual flower on the market.  They bloom very day all summer until cold weather arrives. Unfortunately, they are very susceptible to a fungal disease called aerial phytophera that melts them down to mush if the foliage stays wet in cool weather.  New on the market they year is a variety, ‘Cora,” that is sold as aerial phytophera-resistant.  That means gardeners can begin using vincas in the garden this time of the year instead of waiting until June when temperatures are high and humidity is low.                  

If you chose to use the older vinca selections, it is essential that you mulch around the plants and avoid watering from overhead.  The fungal spores are splashed from the soil. 

            Vincas are available in pink, lavender, red, and white.  Many selections are bicolor.  Vinca is very drought-tolerant and a favorite of butterflies.  Grow them in full sun. 

            Other summer annuals to consider are caladiums, impatiens, and coleus.  All are plants to use in the shade and none are drought-tolerant.  Coleus and caladiums rely on foliage color for their impact.  There are some coleus that are very dark maroon.  They make a striking contrast to light colored plants in the shade garden. 

            Marigolds are an annual flower for the full sun.  They look great in the nurseries now, but rarely recommend them because they inevitably become infested with spider mites as the summer proceeds.  They are better used as an autumn blooming annual.