Curio muirii occurs in the Western Cape. Plants have been recorded from cliffs and steep rocky slopes along the Gouritz River and its tributaries from Meiringspoort to Buffelspoort in the north, to the Gouritz River Bridge in the south. In its northern habitats, plants grow on quartzitic sandstone of the Peninsula Formation but towards the south also on Bokkeveld shale (Cape Supergroup) at altitudes of 50-800 m . The trailing branches form a network, rooted in crevices and ledges becoming drooping. Rainfall can be expected at any time of the year, during the summer usually from thundershowers, and cyclonic rainfall during the winter. Rainfall in its habitat varies, ranging from 300–400 mm per annum. The average daily maximum temperature is 23°C and average daily minimum is 11°C. The summers are hot with temperatures frequently above 30°C. The winters are mild with cold nights but frost is usually absent from the cliff-face habitat.

Fig. 4. Curio muirii in habitat on a south-facing sandstone cliff at Badspoort, south of Calitzdorp, here growing with Bulbine ramosa. 

The plant drawn by Marieta Visagie depicts plants collected at Badspoort, south of Calitzdorp, on south-facing quarzitic sandstone cliffs adjacent to the Calitzdorp Spa, in 1984. Here the plant shares its habitat with other cliff dwelling plants such as Bulbine ramosa, Crassula badspoortensis, Crassula cotyledonis, Crassula muscosa, Crassula perforata, Delosperma badspoortense, Haemanthus coccineus, Tylecodon leucothrix, Albuca thermarum, Cotyledon tomentosa subsp. tomentosa and Tromotriche choanantha.

Fig. 5. Close-up of a Curio muirii plant growing at Meiringspoort.

At Meiringspoort plants are soft and delicate, and grow in association with Bulbine meiringii, Crassula nemorosa, Crassula pellucida subsp. marginalis and Curio ficoides. At Buffelspoort near Ladismith plants share their habitat with Astroloba cremnophila, Crassula rupestris subsp. marnieriana and Albuca buffelspoortensis.

Another population from cliffs near the top of Huisrivier Pass, at about 800 m above sea level, Curio muirii was growing together with Adromischus triflorus, Crassula orbicularis, Crassula rupestris subsp. marnieriana and Pelargonium alternans.

Fig. 6. Curio muirii growing on top of the Huisrivier Pass with Calitzdorp in the background, here growing among quartzitic sandstone rocks, sharing its habitat with Adromischus triflorus, Crassula rupestris subsp. marnieriana, Crassula atropurpurea and Crassula orbicularis. 

Along the lower Gouritz River, plants are more robust and grow commonly on south-facing shale cliffs at the Valsriviermondmond and Groote Heuvel. Here the plants share their habitat with Cotyledon eliseae, Crassula orbicularis, Crassula cultrata, Curio ficoides, Euphorbia pentagona, Haworthia turgida and Gasteria carinata var. thunbergii.

Fig. 7. Curio muirii growing on a shale ledge above the Gouritz River on the farm Valsriviermond together with Crassula orbicularis, Crassula rupestris, Delosperma sp., Euphorbia pentagona and Haworthia turgida (background) Western Cape.