Sempervivum 'Mahogany': Cultivar Profile & Care

Sempervivum 'Mahogany' is a vegetatively propagated hybrid houseleek introduced by Dutch nurserymen in the late 1960s or early 1970s, with stated parentage of S. tectorum × S. arachnoideum that has never been formally published. Its diagnostic feature is a compact rosette 6 to 9 cm wide that flushes a deep mahogany-brown across the entire leaf blade through summer, with red-orange tips that hold contrast against the darker base colour. In winter the rosette returns to greener tones as cold suspends anthocyanin production. Like the rest of the genus, it is fully frost-hardy in temperate climates, freely stoloniferous, and monocarpic on a flowering rosette every 3 to 5 years.

Part of the Complete Sempervivum Guide.

Cultivar Provenance

Trade attribution places 'Mahogany' with Dutch breeders in the late 1960s or early 1970s, an active period for European Sempervivum hybridisation as the alpine trough revival pushed nurseries to expand cultivar ranges beyond wild species. The introducer's name does not appear in the standard Sempervivum Society register for the period, which is unusual and means the cultivar circulates without a registered originator. Catalogue text typically gives parentage as S. tectorum × S. arachnoideum, but the cross has not been published, and the morphology (broad triangular leaves, no cobweb webbing, modest size) is consistent with that pairing without strictly requiring it. A S. tectorum × S. calcareum cross would also produce something close to the plant sold as 'Mahogany'. For the grower the practical implication is twofold: the parentage on the label is plausible rather than verified, and named-clone consistency depends on the supply chain.

Hybrid status carries three downstream consequences. First, seed-grown progeny will not come true; the only legitimate propagation is vegetative. Second, the cultivar is widely produced through tissue culture for the European garden-centre market, and tissue culture sometimes produces somaclonal drift, so two pots labelled 'Mahogany' from different chains can show measurable differences in leaf width or summer pigmentation depth. Third, several near-identical brown-flushing hybrids circulate under the same name in different countries; if you want cultivar consistency, source from a specialist alpine nursery rather than a chain garden centre.

Identification

A fully grown rosette of 'Mahogany' measures 6 to 9 cm in diameter, sitting on the smaller end of the Sempervivum size range and noticeably more compact than its presumed S. tectorum parent. Leaves are 2 to 3 cm long, broadly triangular with a pointed tip, and held in the dense flat phyllotaxy typical of the genus. The defining seasonal trait is colour. From late spring through autumn the leaf surface flushes a deep mahogany-brown across the entire blade, intensifying with direct sun and dry roots, and the leaf tips hold a red-orange contrast against the darker base. The combination is unusual: most red-pigmented sempervivums sit in the wine-red to purple range, while 'Mahogany' takes its name precisely because the dominant tone is the warm brown of the timber. As temperatures fall in autumn the anthocyanin reserve drains back and the rosette returns to a mid-green flushed with rust at the leaf tips through winter. Pink star-shaped flowers, typical of the genus, appear on the central rosette of an established colony every 3 to 5 years on a 15 to 25 cm scape.

Three lookalikes regularly cause confusion in trade.

S. tectorum, the type species and a presumed parent, is larger (rosettes commonly 8 to 15 cm), with broader leaves that are fundamentally green and only red-tipped. The whole-leaf brown flush of 'Mahogany' is absent.

S. arachnoideum, the cobweb houseleek and the other presumed parent, is smaller (rosettes typically 1 to 4 cm), with narrow leaves and the diagnostic white trichome webbing between leaf tips. 'Mahogany' has no webbing.

The cultivar 'Red Beauty' is the closest commercial confusable. 'Red Beauty' is a comparable size, but the dominant colour is a darker red-purple rather than the warm brown of 'Mahogany', and its leaves are noticeably smaller and narrower. Side by side under the same light the two are obviously different; in isolation, a single rosette of 'Mahogany' grown in part shade can read superficially like 'Red Beauty' grown in full sun. Provenance and growing conditions matter for the comparison.

Cultivation

Light. Full direct sun is required to develop the mahogany flush. A minimum of 6 hours of unfiltered sunlight pushes the foliage into its named summer colour; below that threshold the rosette greens out and the cultivar effect is lost. South or southwest exposure outdoors works well. Indoors behind window glass the colour will not develop reliably, because most of the UV that drives anthocyanin accumulation is filtered out before it reaches the leaf.

Substrate. Use the standard alpine mix described in the complete Sempervivum guide: about 60 percent pumice or 3 to 6 mm horticultural grit, 20 percent coarse sand, and 20 percent loam-based compost. The finished substrate should look gritty rather than peaty. Top-dress with 1 to 2 cm of grit around the rosette to keep the lower leaves dry and to suppress moss. pH-neutral conditions are ideal; the cultivar tolerates slightly alkaline limestone-based substrates without issue, which is consistent with possible S. calcareum genetic input.

Water. In containers, water thoroughly when the top 3 to 4 cm of substrate reads dry on a moisture probe, then leave alone until the substrate is dry again. In active spring and autumn growth that pattern lands at roughly once every 7 to 10 days; in summer dormancy and through winter, water minimally or not at all. The failure mode is winter wet, not winter cold. A plant that is stable at minus 25 °C in dry snow will rot at plus 2 °C in saturated compost.

Temperature. Fully frost-hardy. Reliable to about minus 25 °C bone-dry, in line with its likely S. tectorum parentage; in alpine troughs in central European gardens it sits outdoors year-round without protection. Summer heat above 30 °C triggers a temporary growth pause and tighter rosette closure, which is normal and not a sign of distress.

Pot and placement. A 12 to 15 cm shallow terracotta pan suits a single mature rosette and its first generation of offsets. Larger troughs and pans hold a colony cleanly for years. The cultivar performs well in green-roof plantings, paving cracks, and stone walls, and is one of the more reliable brown-flushing selections for outdoor mass display.

Propagation

Vegetative only, by stoloniferous offsets. A mother rosette produces 6 to 15 chicks per growing season on short stolons that lift each chick a few centimetres above the substrate. Once a chick has formed its own roots, typically 4 to 8 weeks after first appearing, sever the stolon with sterile scissors and replant. No callusing period is required because the stolon connection is structurally designed to detach. Establishment takes 2 to 3 weeks.

Seed propagation is not appropriate for this cultivar. As a hybrid of unverified parentage, seed-grown progeny will not match the parent, and any commercial 'Mahogany' raised from seed should be regarded as a different selection sharing the name.

Tissue culture is the standard commercial route in Europe and produces large volumes of uniform stock. Home growers will not need it, but the technique explains why 'Mahogany' is the more affordable brown-flushing cultivar at chain garden centres, while comparably coloured but slower-multiplying selections sit at specialist prices.

Notes

Monocarpy applies as elsewhere in the genus. A flowering rosette of 'Mahogany' dies after seed set, typically every 3 to 5 years on the central rosette of an established clump. The colony does not die; the surrounding chicks fill the gap. New growers regularly mistake the pre-flowering vertical stretch for etiolation. The diagnostic difference is the reduced bract-like leaves on the flowering scape versus full-sized leaves at lengthened internodes on an etiolated rosette. The beginner's guide to succulents covers the cross-genus etiolation symptom in more detail.

Pests and disease follow the genus pattern. Root mealybug is the commonest hidden problem in pot-grown stock; rust (Endophyllum sempervivi) is rare but unrecoverable when it does appear and means the affected plant must be destroyed rather than treated. Inspect new acquisitions for both before introducing them to an established colony.

For cultivar-name consistency, buy from a nursery that propagates from a known mother stock rather than from generic supermarket trays. Two pots labelled 'Mahogany' from different European chains can differ visibly in summer colour intensity, and the named clone with the deepest mahogany flush is the one worth keeping.

See also

• The Complete Sempervivum Guide, the genus pillar covering taxonomy, cultivation, and propagation in depth.
• Beginner's guide to succulents for cross-genus basics on light, water, and the common early mistakes.