Crassula inopina is only known from the southern foothills of the Olifantsberg, on the farm De Breede Rivier, northwest of Worcester, Western Cape Province, South Africa. It grows in rock fissures on partly weathered rocky outcrops. The geology consists of Malmesbury shale and conglomerate. The plants have been recorded at an altitude of between 326 and 440 m above sea level. Rainfall is mainly during winter with an annual mean precipitation of 370 mm. Rainfall usually occurs from May to August.

Crassula inopina grows on exposed, north-facing, steep rocky slopes and low cliffs and often also under the protection of overhangs and in crevices. The stems lengthen to about 100 mm when growing in shade and resemble a form of Crassula perforata.

Fig. 3. LEFT The north-west facing, rocky Malmesbury shale habitat of Crassula inopina, on the farm De Breede Rivier, Worcester, Western Cape. RIGHT Crassula inopina growing in a crevice, in habitat.

The vegetation consists of a mixture of Breede Shale Renosterveld (Fynbos Biome) and elements of Succulent Karoo. It is part of the unique winter-rainfall mosaic vegetation of the mountains and intermontane valleys in the Worcester area, mainly determined by the geology.

Crassula inopina plants grows in full sun or sometimes in the shade of shrubs in its habitat. Common species sharing its habitat include Aloe microstigma, Crassula rupestris, Passerina obtusifolia and Restio gaudichaudianus. Other associated common plants in its habitat include Dodonea viscosa subsp. angustifolia, Euclea undulata, Capeochloa arundinacea, Chrysocoma ciliata, Drimia capensis, Dicerothamnus rhinocerotis, Eriocephalus africanus, Euryops rehmannii, Felicia filifolia subsp. schaeferi, Aizoon africana (= Galenia africana), Heterolepis aliena, Oedera genistifolia, Oedera squarrosa, Othonna perfoliata (= O. amplexifolia), Pteronia incana, Pteronia paniculata, Anthospermum aethiopicum, Agathosma ovata, Thesium subnudum, Selago glutinosa, Wahlenbergia tenella and Roepera flexuosa (= Zygophyllum flexuosum). Succulents are commonly encountered in exposed rocky outcrops. These include Adromischus filicaulis subsp. marlothii, Crassula atropurpurea var. muirii (= C.  atropurpurea var. rubella), Crassula rupestris, Conophytum ficiforme, Delosperma pageanum, Drosanthemum hallii, Drosanthemum hispidum, Euphorbia mauritanica, Mesembryanthemum longistylum, Pelargonium carnosum, Pelargonium rapaceum, Ruschia caroli and Tylecodon paniculatus. Fern species include Cheilanthes capensis and annual species such as Cineraria lobata occur. Geophytes include Boophone disticha, Eriospermum capense, Freesia refracta, Lapeirousia pyramidalis, Xenoscapa fistulosa, Oxalis pes-caprae and Oxalis convexula.

Fig. 4. Crassula inopina in flower growing in a crevice in its rocky Malmesbury shale habitat. Note the rouned inflorescence, and 4-ranked, glaucous succulent leaves with dots on the surface and a row of stiff hairs on the margins.