Mesembryanthemum excavatum is a prostrate plant bearing succulent, cylindrical leaves. The channelled leaves have small water cells on their surfaces. Leaf dimensions are about 20 mm long and 5 mm wide. The leaves are often dry when the plant flowers.
The stalked, yellow flowers grow clustered at stem-tips. Flower diameter is about 15 mm. Flowering happens from late spring to early summer.
The species distribution is inland in the Western Cape from Ceres through the Karoo and Little Karoo into the far south of the Northern Cape Karoo and the west of the Eastern Cape. The photo was taken on Minwater near Oudtshoorn.
The habitat is arid scrub, Tanqua Karoo and succulent Karoo in clay soils, notably disturbed spots. The species is not considered to be threatened in its habitat early in the twenty first century (Vlok and Schutte-Vlok, 2015; iNaturalist; http://redlist.sanbi.org).