Mentzelia albicaulis (White-Stem Evening Star) - photos and description





Example of a shallowly-lobed, upper stem leaf


General: An erect annual with stems simple or branching mid to upper stem. Plants are rough-hairy. Stems whitish in colour.

Flowers: The flowers are terminal, yellow, with 5 petals, corolla small with petals about 5 mm long. We were unable to photograph a plant in flower. There were spent flowers on many of the plants, and as you can see from the photos, there are mature flower buds on most plants. However, we saw not a single flower open in daylight. Thinking this may be a species that blooms in the evening, we stayed at the site until dark, no flowers opened, and visited the site just before sunrise the following morning and again no flowers were open. Apparently the flowers only open when photographers are not present :(

We have only ever found this plant on one steep slope in Grasslands National Park. The population is extremely variable, revisits in two subsequent years found no plants.

Leaves: Leaves are alternate, sessile, linear to oblong in shape. Leaves on larger plants with a few shallow lobes. Smaller leaves entire. We measured a leaf at 4 cm long and 5 mm wide.

Height: Height listed in Flora of the Great Plains to 40 cm, we measured plants to 18 cm tall.

Habitat: Dry hillsides.

Abundance: This plant is extremely rare, ranked as an S1 (as of 2021) by the Saskatchewan Conservation Data Centre.

Origin: Native.

When and where photographed: Took the above photos June 20th, on a very steep, south-facing, dry, eroded clay slope, badlands in short grass prairie, west block of the Grasslands National Park, about 350 km southwest of our home in Regina, SK.