Strumaria chaplinii forms a close alliance with S. discifera and S. leipoldtii and more remotely so with S. villosa, all of which occur further north in the Western Cape Province. Each of these species has densely pubescent leaves and similarly-sized, predominantly white, stellate flowers. The flowers of S. chaplinii are characteristically flat and open, with plane-surfaced tepals. The style is broadest at the extreme base and extends smoothly upwards without the sculpturing found at the base of the style in S. discifera. The fleshy inner scales of its bulb are white, easily distinguishing it from S. villosa, which has yellow-fleshed bulbs. The pubescent adaxial leaf surface distinguishes it from the smooth-surfaced, densely fringed leaves of S. leipoldtii.
Bulb solitary, subglobose, 15-20 mm across, with brown fibrous outer tunics, whitish within; neck extending up to 30 mm. Leaves absent at anthesis, 2, prostrate, narrowly obovate-oblong to lorate, 15-65 x 5-10 mm; adaxial surface green, covered with 0.2-6.0 mm long, white, patent hairs; abaxial surface glabrous, green or flushed with red proximally; subtended by a subterranean amplexicaul cataphyll and non-amplexicaul prophyll. Inflorescence widely spreading, 40-150 mm across; scape somewhat flexuose, 35-100 mm long, 2-3 mm diam., green to pinkish with a grey bloom, abscising at the base in fruit; spathe valves linear-lanceolate, 10-30 x 3-7 mm; bracteoles up to 20 mm long. Flowers 4-14, spreading, stellate, white with a reddish or greenish-brown dorsal median stripe on each tepal, ageing to darker shades of pink, scentless; pedicels straight to upwardly curved, 20-80 mm long, concolorous with the scape. Tepals free to base, outspread, ovate-lanceolate, 5-6 x 1.5-2.75 mm, plane-surfaced. Stamens slightly shorter than the tepals, spreading; filaments separate, adnate to the broadened style base with the inner whorl attached higher up than the outer, both whorls somewhat bulbous-based, tapering distally; anthers subcentrifixed, 2 mm long and wine-red before opening; pollen whitish. Ovary with 1-4 ovules per locule. Style up to 5 mm long, equalling the stamens, tapering smoothly upwards from a broad depressed-conoidal base, with nectar collecting in 3 droplets between the base and inner filaments. Seeds 3.0-3.5 mm diam.
Confined to granite outcrops along the west coast where the bulbs are densely aggregated in shallow humus-rich soil, around the margins or in fissures of large boulders. Strumaria chaplinii grows sympatrically with S. tenella subsp. tenella in Langebaan but is usually in seed when S. tenella begins to flower in May. Apart from a rich bulbous flora, the granite rocks also support a dwarf succulent community. The species is currently under threat from coastal development in the Langebaan area.