Geniostoma kaalae is a shrub or small tree, reaching heights of 2–4 meters, occasionally up to 6 meters. Its stems are cylindrical and dichotomously branched, with a surface ranging from short–hispidulous to glabrous. The leaves are opposite and simple, with broadly oblong-elliptic to elliptic–obovate blades, measuring 6–17 cm in length and 2.5–7 cm in width. The leaves have a rounded to broadly obtuse apex, sometimes short-acuminate, and a weakly cordate to obliquely truncate base. The upper leaf surfaces are glabrous, while the lower surfaces are sparsely to moderately short–hispidulous. Petioles are 0.8–2.5 cm long, with similar hairiness. The flowers occur in terminal inflorescences, with 9–25 flowers in open paniculate cymes. The inflorescence structure includes recurved peduncles and pedicels that elongate in fruit. Flowers can be perfect or functionally unisexual, featuring a 5-merous calyx with ovate–deltate lobes and a campanulate to rotate corolla that is green to yellowish green, 10–13 mm long. Stamens are exserted, and the ovary is superior or partly inferior, leading to broadly ovoid capsules as fruit. These fruits are 12–20 mm long, 2–2-valved, not keeled, apex with a beak 1.5–2.5 mm long, septicidal to sub–sub-septifragal, maturing to green with or without a black–purple tinge, usually becoming brown-–black when over–mature. The seeds are brown, 2.5–2.6 mm long, ± winged at both ends or all around, embedded in juicy orange to red pulp, numerous, ellipsoid to subglobular, intruded on the hilar side, brown to black, endosperm thick, fleshy, oily, proteinaceous, with saccharose or hemicellulose, embryo small, straight. It is found primarily on ridges in diverse mesic forests and occasionally in wet forests between 450–950 meters.