The
photo at right shows a close-up of the flowers and young siliques of Lyall's
rockcress as seen below the summit of Table Rock, Monument Rock Wilderness..........September
5, 1999. Note how the silique ascends sharply upwards.Lyall's rockcress is an attractive perennial wildflower with several erect stems arising 10-25 cm high from a tuft of basal leaves. The stems and leaves are either glabrous throughout or they may be sparsely to densely covered with appareled, simple to 2-forked or branched hairs. The numerous basal leaves form a basal rosette. The basal leaves are either glabrous or sparsely haired and vary in length from 6-30 mm long and are 1.5-5 mm wide. They are green in color and fairly fleshy and have elliptic-oblanceolate blades with entire margins. The several stem leaves are sessile with heart-shaped bases and are narrowly oblong to oblong-ovate in shape, measuring 10-20 mm long and 2.5 mm wide.
The inflorescence is a 3- to 15- flowered raceme of purple flowers. The purplish sepals are 3-4 mm long and either glabrous or sparsely haired with long hairs. The petals are 6-10 mm long while the pedicels are 5-10 mm long. The fruits are siliques from 2-6 cm long and 2-3 mm wide. They are straight or arched and are held steeply erect or ascending.
Drummond's rockcress (Arabis drummondii) is similar to Lyall's rockcress and there is a potential that both species can be found at the same site. They are probably easiest to identify when the fruits are maturing. Drummond's rockcress ranges from 30-80 cm high, has numerous overlapping stem leaves and with erect, glabrous siliques from 3-9 cm long ad 2-3 mm wide.
Lyall's rockcress is found on rocky ridges, cliffs and in drier meadows in the subalpine and alpine zones of the mountains.
Lyall's rockcress may be found from British Columbia south through the Cascade Mts. to California and east through the mountains to the Rocky Mts. from Albert south to Utah.
