Sand Verbena

Rare Plant Profile – Small-flowered Sand-verbena (Tripterocalyx micranthus (Torr.) Hook.)

Small-flowered sand-verbena (Tripterocalyx micranthus (Torr.) Hook.) is an annual herb in the Nyctaginaceae (Four O’clock) Family[1]. It has many trailing, glandular-hairy stems that can measure up to 60 cm long, and has opposite, elliptical to egg-shaped leaves[2]. Clusters of tiny, greenish- to pinkish-white tubular flowers, with 5 petal-like sepals, emerge from leaf axils[3]. Rigid stems and thick leaves reduce the potential for water loss, making small-flowered sand-verbena well adapted to dry environments[4]. Seeds are adapted to drought conditions and can survive in a dormant state for 2-3 years until moisture and temperature conditions are right for germination[5].

In Canada, small-flowered sand-verbena is restricted to dry, well-drained, bare, or sparsely vegetated, upland habitats, particularly in loose sands of dunes, sandhills, and along river valley walls and floors in southeastern Alberta and southwestern Saskatchewan[6].  Small-flowered sand-verbena habitat can be characterized as a dynamic landscape mosaic, in which habitat mosaics represent large or extensive areas within which patches of disturbed habitat appear and over time become stabilized, where suitable open habitat moves around the entire habitat mosaic in response to disturbances.[7] Currently, habitat is indirectly threatened through the reduction of habitat suitability as a result of increased stabilization, which is due to weed invasion, as well as changes in land uses and land management that result in disrupting  fire, flood and grazing regimes.

Small-flowered sand-verbena is  listed as Endangered under Canada’s Species at Risk Act because low population sizes occupy very few sites and population numbers fluctuate greatly from year to year[8]. For the same reasons, in Alberta and Saskatchewan it is ranked as S2, or Imperiled[9], and listed as Threatened on Alberta’s Wildlife Act Regulations and Endangered on Saskatchewan’s Wild Species at Risk Regulations.  In 2012, the Government of Canada published the small-flowered sand-verbena’s federal recovery strategy, and concurrently, the Government of Alberta published a provincial recovery plan for this species[10].

Photo by L. Allen
Photo by L. Allen


[2] Kershaw, L.; Gould, J.; Johnson, D.; Lancaster, J. 2001. Rare vascular plants of Alberta. Univ. Alberta Press, Edmonton, Alberta and Nat. Resour. Can., Can. For. Serv., North. For. Cent., Edmonton, Alberta

[3] Ibid.


[5] Ibid.