Sizzling Annuals for Texas Summers

By William Scheick

Contributing Editor

Now and then I think there’s something a little sad about annuals. Their glorious beauty is oh-so brief. Like us, annuals get just one go-round.

So I tend to find perennials more comforting. Even so, I love annuals, too. It would be a big loss if somehow we were deprived of the splendor that annual flowers bring to our lives each year.

Actually, the single-year life cycle — from seed, to plant, to flower, to reproduction and death — is not identical for all annuals. Some annuals last longer than others. Hardy annuals, such as snapdragon, are often among the earliest and the latest to be planted in many Texan gardens. Often one batch can start soldiering in the cold of late February and then a new batch can brave the cold from early October.

For most Texas gardeners, however, the cold hardiness vs. tenderness of annuals is less a worry than is their heat tolerance. Many annuals need regular access to water for ample flowering, so they often fail during our droughty summers despite our efforts to provide moisture. Some die because transpiration (the normal loss of water through leaves), accelerated by heat and wind, often exceeds their roots’ osmotic ability to absorb moisture from the soil. Others die from our well-intentioned efforts to keep them hydrated, resulting in various fatal root diseases. Also for many annuals, our high summer temperatures impede photosynthesis, the plants’ life-sustaining means of carbohydrate production.

So particularly whenever our Texas springs are suddenly hijacked by skyrocketing and brutal summer-like temperatures, a large number of our favorite annuals simply collapse. Even durable zinnias, which now come in an amazing array of floral shapes and colors, can seem to be here today and gone tomorrow once premature summer temperatures ruin spring.

Even so, there are easy-to-grow annuals that can put on a first-class show during our Texas summers. Here are four of my favorite summer-thriving annuals.

Portulaca [pronounced poor-two-LAH-kah], also called purslane or rose moss or sun jewel, heads my list of summer-through-autumn annuals. Portulaca includes more than one species hailing (it is believed) primarily from Central and South America, but whatever the species, this amazing plant must be seen to be believed. When glimpsed for the first time on a broiling summer day, a first reaction to portulaca’s floral spectacle just might be, “That’s utterly impossible.”

But possible it is! With thick, fleshy foliage, portulaca thrives in poor sandy (draining) soils beneath blazing summer sunlight. In short, it excels where most other annuals quickly wither. An extremely low-maintenance plant, rose moss will actually fail to bloom if it receives too much water or if it receives insufficient sunlight. A limited amount of mulch, though, helps keep its roots a bit cooler.

Most portulacas stay low to the ground, and when occasionally leggy can be easily snipped back into desired contour. So rose moss makes a good summer choice for border edges. The only problem with this positioning, in my opinion, is an odd one: the radiant varied floral colors of sun jewel tend to steal the show. They are so vividly “hot” that they arrest a viewer’s attention instead of guiding it from an edge farther into a garden bed. On the other hand, by mid-summer portulacas might be the only show still performing in your garden.

Gomphrena [pronounced gum-FREE-nah], also known as globe amaranth, isn’t as sun-proof as portulaca, but it’s also a topnotch summer-through-autumn annual for Texas. This Central American tropical has minimal needs: plenty of sunlight, excellent drainage, occasional watering.

Not all gomphrenas are equal, though. Their height varies, ranging from six inches to almost four feet, depending on the cultivar. Ideally, a product tag will indicate what you might expect.

Globe amaranth, which should be spaced about eight inches apart, bears numerous clover-like floral balls in an amazing range of nearly iridescent colors. There are so many available color variations that, for me at least, choosing one is impossible. It must be hard for butterflies, too, if I’m any judge of their behavior.

As a bonus, incidentally, these flowerheads can be cut and brought indoors, where they look great in a vase for about a week. Then they can be dried.

Mulch gomphrenas lightly and water only sparingly, especially during humid weather, or else there might be a risk of leaf spotting and powdery mildew. ‘Fireworks’ gomphrena received the FlameProof and the Best New Introduction awards from the Dallas Arboretum.

Penta [pronounced PEN-tah], also known as Egyptian star cluster, is not technically an annual in frost-free regions, but it’s commonly grown as a summer-through-autumn annual in most of Texas when not overwintered as a container plant. It is much easier to keep going in the heat than its eye-catching beauty might suggest. All it needs is sunlight, water when dry and a little monthly feeding in well-draining, well-composted beds.

Penta’s floral “shooting stars,” ranging from white through a variety of reddish to purplish tones, crown equally showy green foliage. In most of Texas, pentas grow to only about two feet or so and should be spaced about two feet apart. Pentas are not quite as drought tolerant as gomphrenas, but they sometimes withstand a light frost.

They are also easy to propagate from cuttings, and their flowerheads often last for several days indoors in a vase. Pinching off the flowers (deadheading) fosters re-blooming — that is, if you can get your local hummingbirds to let you get that close to their/your pentas.

Hyacinth bean (Dolichos lablab), a prolific twining vine also known as Egyptian or lablab bean, grows so easily and rapidly that it could stand in for the magical plant featured in the fairytale about Jack and the beanstalk. It’s a perennial, technically, but so short-lived and cold sensitive that it performs like a non-invasive annual in most of Texas. Plant hyacinth beans and simply watch them sprout.

What a performance this vine puts on as it reaches for the sky! How high will it climb? I’ve seen hyacinth bean vines tower over 10 feet in our state. So they need ample space and also strong support, especially later when they produce an abundance of heavy purple pods. The raw pods and seeds, I should mention, can be dangerous to pets.

While the foliage of this vine can’t get enough of our summer sunlight, its roots prefer to be more sheltered. Shielding the roots by locating them on the northerly side of a shadow-casting fence or trellis will conserve soil moisture and coolness. While this bean is not fussy about soil, drainage is crucial and so is watering when dry.

The faintly scented pink or white pea-like flowers of hyacinth bean bloom from mid-summer through fall in Texas. Their abundant clusters are showy and, if you are lucky, they just might distract your resident hummingbirds long enough for you to deadhead their/your pentas.

The pincushion flower (Scabiosa atropurpurea) is a fragrant annual that can put on quite a lovely show during our scorching Texas summers. Although its skinny two- to three-foot stalks usually droop, it’s an easy-care plant that prospers in slightly alkaline conditions.

Apparently, though, the pincushion flower is too much of a good thing, at least in some parts of our state. It has naturalized in North Central Texas, where it is now considered “a serious threat” as an invasive species. According to the Botanical Research Institute, Scabiosa atropurpurea “is currently taking over roadsides and adjacent areas in the northern part of North Central Texas (e.g., Collin County) and has the potential of becoming one of the most destructive invasive exotics in the area.”

Why is it considered so destructive? The answer is that wherever pincushion flower has naturalized, it has tended to form a monoculture. In other words, it dominates a habitat so thoroughly that it crowds out other plant species.

Annuals for Every Garden, ed. Scott D. Appell. Brooklyn Botanic Garden, 2003.

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