Diascia namaquensis is a soft herbaceous annual that grows up to about 400 mm tall. The stems may branch from the base or remain unbranched. The leaves are mostly arranged in a basal rosette and become smaller towards the tips of the stems. They are obovate to elliptic in shape, up to 50 × 12 mm in size, and are irregularly lobed or divided. The flowers are distinctive and showy and bilaterally symmetrical. The calyx lobes are long-pointed and vary from tail-like to curved and sickle-shaped. The corolla is usually salmon, pale orange, purple-red or maroon, and rarely white. The flower limb is 10–20 mm long, the side and upper lobes slightly smaller. Below the upper and side lobes of the corolla tube there is a yellow, elliptical translucent patch, often called a “window”, sometimes accompanied by one or two much smaller patches. Most flowers have two long and widely spreading spurs, pointing sideways when the flower is viewed from a frontal position, measuring 5–20 mm in length. Although forms with short, blunt spurs may also be present in the same population. The stamens project forward and are somewhat straight. The rear filaments are thickened or slightly bent backwards near the middle and are mostly hairless, except for a small tuft of purple hairs at the bend.

Fig. 2. Plants of Diascia namaquensis are usually floriferous when grown in full sun and with ample watering. Here shown in frontal view (A) and from behind showing the characteristic horizontal held spurs (B).

The fruit is an ovoid capsule, 5–7 mm long, which is equal to or longer than the calyx. The seeds are very small, black, and shiny, with a rough, wrinkled surface. Flowering takes place mainly in spring, from August to October, depending on the timing and amount of rainfall.

Diascia namaquensis can be recognised by its combination of large, colourful flowers, the presence of the usually two long spurs, and the yellow translucent “windows” in the corolla tube. The only other species with which it can be confused in its native range are two, formally undescribed, species that differ in the orientation, length and thickness of their spurs. Most annual Diascia species are found in the winter-rainfall regions of western South Africa, while perennial species mainly occur in the eastern, summer-rainfall parts of the country. This geographic separation further helps to distinguish D. namaquensis from related species.

Fig. 3. Frontal view of a flower (left) and flower viewed from behind (right) showing morphological structures of the flower (spurs, windows, anthers).