Field Guide
Tripterocalyx micranthus
By almost every measure, the small-flowered sandverbena is not what it appears to be
At first glance, this plant’s double-barrelled name seems a misnomer. The small-flowered sand-verbena boasts a large and quite lovely peach-coloured bloom. A second, somewhat closer glance, though, reveals that the tiny white dots at the end of succulent green tubes are the actual flowers. The attractive, peachy two-centimetre ovoid that first catches the eye is in fact the seed pod. It seems to have evolved this way to catch the wind. Little about this plant is as it appears.
Tripterocalyx micranthus, as it is known to botanists, has a hearty will to live in Canada: native only to Saskatchewan and Alberta, it thrives in desert-like conditions on unstable sand dunes, preferably south-facing. (It should not be confused with the genus Verbena, with about 250 species of annual and perennial vascular or semi-woody flowering plants, including the ubiquitous blue vervain and, of course, lemon verbena.) An opportunistic annual, it is able to withstand prolonged drought thanks to seeds that refuse to germinate in dry conditions. A small-flowered sand-verbena seed can lie in wait for several years, through intensely cold winters and baking hot summers, until conditions are favourable. It manages this trick thanks to a tough wrapper around the seed that dissolves only with prolonged exposure to moisture. This increases the likelihood the plant will have enough water as it rapidly germinates, flowers and sets seed. Speed is essential in such conditions: a plant’s entire lifespan is only two to three months. In a world of shifting sands, that is an eternity.
Known to many as “sand puff,” the small-flowered sand-verbena is part of a small genus of flowering plants in the four o’clock family (Nyctaginaceae), thus named for their shared trait of flowering only late in the afternoon and closing before morning. While most of these types of flowers, including bougainvillea, are found in the tropics, a few flourish in the southern United States, into the Midwest. Only one is native to Canada. And it is a strange thing to see this “tropical flower” on the harsh, dry prairie.
When flourishing, it is an appealing plant, erect and compact, with stiff reddish stems and somewhat elliptic, heavily veined opposing leaves. (Its thickness and rigidity minimize moisture loss.) A closer look reveals grains of sand adhering to the sticky stems, which seems to have evolved as a means of girding and protecting it from buffeting windborne sand. Clusters of white-green trumpet-shaped flowers only about six millimetres across offset the eye-catching spongy peach-coloured fruit that features three slightly raised, very thin wings. These enable the seeds to be carried aloft for some distance as they seek the hospitality of similarly inhospitable dunes downwind. (Some research suggests these wings also work in water, as seeds have been noted being carried downstream on the Saskatchewan River, for instance. There are hopes that undiscovered colonies may dot the riparian beaches and dunes, though none have been spotted yet.)
Despite its robust adaptations and patient opportunism, the small-flowered sand-verbena has been listed as endangered in Canada’s Species at Risk Act database since 2002. Threats are largely due to habitat loss (including natural sand dune stabilization followed by encroachment of woody vegetation) in combination with an increase in invasive aliens and habitat degradation from industrial uses and recreational activities. Also at risk are many of its companion species, including smooth goosefoot and slender mouse-ear-cress, as well as both the dusky and the pale yellow dune moth. (I confess I include this list mostly for the sake of repeating their lovely names.) Still, given the plant’s capacity to wait out droughts, it is virtually impossible to have a complete picture of the species’ health. An Alberta plant count during the nasty drought of 2001 found only one plant extant; two years later, the count in the same region was 3,600 plants. Estimates today suggest that among a dozen “sand dune complexes” between Taber, Alta., and Lake Diefenbaker, Sask., there may be 10,000 plants. It is a curious plant, not really what it appears. Called verbena, but not a Verbena. Tough and resilient, but fragile. Highly evolved and enduring, yet fleeting and ephemeral. Showy and attractive, but with only minuscule blossoms. Perhaps this is why I find the small-flowered sand-verbena so fascinating.