Editor's note: John P. Begeman retires this week after 13 years as the urban horticulture agent for the University of Arizona-Pima County Cooperative Extension. Next Sunday will be his final column.
Tucson in the summer sun and heat is no place for the faint-of-heart when it comes to garden plants. Flowers, in particular, have to be tough to survive. Here are some of the best for summer color — ones that will not just survive but actually thrive in the scorching sun and withering heat of the desert Southwest.
Vinca, also referred to as Madagascar periwinkle, is one of the best choices for summer color. The leaves are a rich glossy-green and provide the perfect backdrop for the showy star-shaped flowers.
Selections are available in a range of colors from red and hot pink to lavender, purple and white. A small 6-inch potted vinca will quickly grow to a height and width of 18 to 24 inches. Their mounding form makes them ideal for growing in broad containers.
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Flowering is continuous through summer and fall. Full sun is a must for vinca. They love the heat and are one of the most drought-tolerant annuals, although they still need daily watering when temperatures exceed 90 degrees.
A word of caution: Plant vinca in pots with loose, well-drained soil. They are prone to root-rot in poorly drained, waterlogged soils.
Next on my list of favorite summer bloomers is portulaca, also known as moss rose. Portulaca is a succulent with thick button-size leaves.
Two distinct types of moss rose are available. One has small, elongated, needlelike leaves; the other has broader, oval-shaped leaves. The broader-leafed form is, in my estimation ,the better of the two, with more attractive foliage and more flowers.
Both types have bright, nearly florescent quarter-size blooms in a rainbow of colors. Some have bi-colored petals. Most are single flowers, but some are roselike double flowers. All are heat and full-sun tolerant, but they still require daily watering.
A word of caution: Moss rose bloom only when it's sunny. Usually, that's not a problem in Arizona. But during our summer monsoon, afternoon clouds will cause the flowers to close, often for the remainder of the day.
If you're looking for a summer annual with true-blue flowers and a true penchant for sun and heat, try Nierembergia. Also known as the cup flower because of its bowl-like shape, Nierembergia flowers are yellow-throated, the perfect color combination with their blue, purple or white petals depending on the variety. The lacy, needlelike foliage of Nierembergia is also attractive.
This flower tolerates full sun but looks and flowers its best if provided some afternoon shade. Shaded flowers will not close. Other heat-tolerant summer annuals I recommend include zinnias, dusty miller, globe amaranth, celosia and salvia splendens.
Some garden centers and home supply stores still have a few winter and spring holdovers on their shelves, including petunias, dianthus, ageratum, alyssum and cosmos. Marigolds will flower reliably only through June in the low desert. Don't choose these holdovers unless you live above 4,000 foot elevation, where summer heat is less intense.
Demonstration
"Composting & Fertilizing" will be the topic of this week's gardening demonstration at 1 p.m. Wednesday at the Wilmot Library, 530 N. Wilmot Road. It is the last demonstration of the season. Presentations will resume in the fall.