Crassula undulata is a compact, densely branched shrublet in the genus Crassula (family Crassulaceae), native to the winter-rainfall mountains and karroid scrub of western South Africa. This elegant, geometrically neat plant earns its common name of “doily crassula” from the tidy, doily-like arrangement of its leaves in precise opposite rows along the stems. While it will never rival Crassula ovata for mainstream popularity, it is increasingly appreciated by collectors and water-wise garden designers for its fresh green foliage, its delicate silvery-edged leaves, its showy white-and-red flowers, and its excellent performance as a ground cover in Mediterranean and semi-arid climates. It is also a plant surrounded by persistent nomenclatural confusion that deserves careful untangling.
Taxonomy and Naming History — Untangling the Confusion
Crassula undulata was described by Adrian Hardy Haworth in 1803 in Miscellanea Naturalia. The accepted name according to POWO is Crassula undulata Haw.
However, the same plant is widely known — particularly in South African horticultural literature and on PlantZAfrica (SANBI) — as Crassula dejecta Jacq. (described by Nikolaus von Jacquin in 1805). Under POWO’s classification, Crassula dejecta is a synonym of Crassula undulata. The two names refer to the same species, and gardeners may encounter either name depending on the source.
The full synonymy includes:
- Crassula dejecta Jacq. (1805) — the name used by SANBI and many South African sources
- Crassula undata Haw.
- Crassula albiflora Sims
- Curtogyne dejecta (Jacq.) DC.
- Curtogyne undulata (Haw.) Haw.
- Curtogyne undosa Haw.
- Rochea dejecta (Jacq.) Steud.
- Rochea undulata (Haw.) Steud.
- Purgosea undulata (Haw.) Sweet
Beware of name confusion
The epithet *undulata* (“wavy”) appears in several different Crassula contexts, which causes significant confusion in the trade:
Crassula undulata Haw. — the species treated in this article. A small, densely branched shrublet with slightly fleshy green leaves and white-and-red flowers. Native to the Western and Northern Cape.
Crassula arborescens subsp. undulatifolia Toelken — the “Ripple Jade” or “Blue Bird”, a completely different plant: a large, tree-forming subspecies of Crassula arborescens with wavy, blue-grey leaves. Often mislabelled as Crassula ovata ‘Undulata’. Treated in our article on Crassula arborescens.
Crassula ovata ‘Undulata’ — a cultivar name sometimes applied to plants with wavy leaves, which are usually actually Crassula arborescens subsp. undulatifolia and not Crassula ovata at all.
None of these three plants are the same species. If the plant is a small, densely branched, upright shrublet with slightly fleshy green leaves, bead-like marginal hairs, and white flowers with red centres, it is Crassula undulata. If it is a large, tree-forming plant with strongly glaucous, wavy, blue-grey leaves, it is Crassula arborescens subsp. undulatifolia.
Etymology
The genus name Crassula derives from the Latin crassus (“thick, fat”). The specific epithet undulata means “wavy” in Latin, referring to the leaf margins, which can be slightly undulate — though this character is variable and not always obvious. The synonym dejecta means “cast down” or “drooping” in Latin — possibly referring to the plant’s natural habit of growing on overhanging rock ledges, or to the downward-curving hairs visible on young stems. The common name “doily crassula” likens the neat, geometric leaf arrangement along the stems to the intricate pattern of a decorative doily.
Natural Habitat and Distribution
Crassula undulata is native to the western regions of South Africa, distributed from the Riviersonderend Mountains and the Stellenbosch area in the Western Cape northward through the Cedarberg to Springbok in Namaqualand (Northern Cape). It grows on large rock outcrops, on ledges and in crevices, typically on the south or southwest-facing aspects of mountains — the cooler, more shaded slopes in the Southern Hemisphere. This preference for shaded, sheltered cliff positions distinguishes it from many other Karoo crassulas that favour hot, north-facing exposures.
The species is not threatened (Least Concern). It has naturalised as a garden escapee in the northern North Island of New Zealand — a testament to its vigour and adaptability once established.
Climate across the natural range
Rainfall. The range is predominantly winter-rainfall, with annual totals of 200–500 mm concentrated in the cooler months (May–August). Summers are hot and dry. The Cedarberg and Namaqualand portions of the range receive the lowest rainfall (150–250 mm); areas near Stellenbosch and the Riviersonderend receive somewhat more (350–500 mm).
Temperatures. Summer maxima reach 30–40 °C in exposed Karoo habitats, but the species’ preference for south-facing slopes and rock crevices means that individual plants often experience moderated conditions with more shade and cooler airflow than the surrounding landscape. Winter minima fall to 2–7 °C, with frost possible in the inland montane parts of the range. Hardy to approximately –3 °C to –4 °C in dry conditions (USDA zones 9b–11b).
Botanical Description
Growth habit and stem
Crassula undulata is a neat, densely branched, erect perennial shrublet, typically reaching 30–40 cm tall, forming a compact, bushy mound. Stems are slightly woody, upright, with small downward-pointing hairs on the young growth that give the stems a faint silvery dusting (visible under a hand lens). The overall form is tidy and geometric — the plant naturally maintains a dense, well-proportioned shape without pruning, which makes it visually effective both as an individual specimen and as a massed ground cover.
Leaves
The leaves are opposite, densely arranged in neat rows along the stems, more or less the same size throughout the plant (no marked size gradation from base to tip as in Crassula capitella). They are slightly fleshy, ovate to oblong, green to yellowish-green, and frequently tinged red — particularly under stress from strong light, cold, or drought. The most distinctive character is the row of rounded, bead-like hairs along the leaf margins, which gives each leaf a delicate silvery edge. These marginal hairs are minute and best appreciated under magnification, but their collective effect is visible to the naked eye as a fine silvery outline framing each leaf.
Flowers
The flowers are a genuine ornamental feature — more showy than those of most small Crassula species. They are white, sometimes tinged pink, with conspicuous red sepals, red ovaries at the centre, and red anthers that age to brown. The effect is of a white star with a vivid red eye — clean, bright, and visually striking against the green foliage. Flowers are produced in dense, rounded to flat-topped clusters at the stem tips in summer (November–February in the Southern Hemisphere). The SANBI description notes that the red centres of the open flowers give the inflorescence its most distinctive ornamental quality.
Cultivation Guide
Light requirements
Sun or semi-shade. Unlike many Karoo crassulas that demand full sun, Crassula undulata naturally grows on shaded, south-facing rock faces and does well in positions that are open to the sky but may only receive direct sun for part of the day. This makes it a versatile plant for garden positions that are bright but not in baking afternoon sun — a quality shared with few other Crassula species. It also grows well indoors in bright light.
Temperature and hardiness
USDA hardiness zones 9b to 11b. Hardy to approximately –3 °C to –4 °C in dry conditions. Not suited to sustained freezing or wet cold. In mild-winter Mediterranean climates, it can be grown outdoors year-round in a well-drained position.
Substrate and watering
Well-drained soil, enriched with well-rotted compost. Crassula undulata is less demanding about substrate than many Karoo species and tolerates a wider range of soil types, provided drainage is adequate. Water moderately during the growing season; reduce in summer. The species is easy to grow — SANBI describes it as “no exception” to the general ease of Crassula cultivation. It responds well to frequent low doses of organic fertiliser during the growing period.
Garden use
The neat, bushy form and dense leaf coverage make Crassula undulata an excellent water-wise ground cover when planted en masse. It also works well as an edging plant, in rockeries, in fynbos-style gardens, and as a container plant. The combination of fresh green foliage, silvery-edged leaves, and white-and-red flowers gives it a refined appearance that contrasts pleasantly with the bolder textures of Crassula ovata, Aloe, or Cotyledon species in mixed succulent plantings.
Propagation
Stem cuttings — the standard method. Take cuttings of 10–15 cm in early autumn, allow to callus for several days to a week, and strike in well-draining river sand or gritty mix. SANBI notes that rooting is slower for this species than for some other crassulas (two to three months rather than two to three weeks), owing to the slightly woody stem tissue. Use low, intermittent misting if available. Ensure the rooting area has good ventilation and approximately 50% natural light.
Division — mature plants produce offsets that can be separated.
Seed — viable; dispersed by wind in the wild. Fine dust-like seeds, slow germination.
Pests and Diseases
The species is robust and not particularly pest-prone. Standard Crassula issues apply: mealybugs (the most common pest), root rot from overwatering, and occasional fungal problems in humid, stagnant conditions. The dense branching can trap humidity; ensure good airflow around the base of the plant.
Toxicity
As with all Crassula species, treat as potentially toxic to cats, dogs, and horses (ASPCA). No specific ethnobotanical or medicinal use is recorded for Crassula undulata.
Frequently Asked Questions
Is Crassula undulata the same as Crassula dejecta?
Yes — they are the same plant under different names. POWO (Royal Botanic Gardens, Kew) accepts Crassula undulata Haw. (1803) as the valid name, with Crassula dejecta Jacq. (1805) as a synonym. However, SANBI’s PlantZAfrica uses Crassula dejecta. Both names appear in the trade and in horticultural literature; they refer to the same species.
Is Crassula undulata the same as the Ripple Jade?
No. The “Ripple Jade” is Crassula arborescens subsp. undulatifolia — a completely different species. Crassula undulata is a small, densely branched shrublet (30–40 cm) with green, slightly fleshy leaves and white-and-red flowers. Crassula arborescens subsp. undulatifolia is a large, tree-forming plant (up to 1 m) with strongly blue-grey, wavy, glaucous leaves. The similar-sounding names cause frequent confusion, but the plants are easy to distinguish visually.
Can Crassula undulata grow in shade?
More than most Crassula species, yes. In its native habitat, Crassula undulata grows on south and southwest-facing rock faces — the cooler, more shaded aspects. It performs well in positions that are bright but receive only a few hours of direct sun per day, making it a good choice for semi-shaded garden beds, the south side of a house (in the Southern Hemisphere), or bright indoor positions.
Is the doily crassula a good ground cover?
Yes — it is one of the best small Crassula species for ground cover use. Its dense, neat, naturally compact growth habit means it covers ground evenly without becoming leggy or untidy. Planted en masse in well-drained soil, it forms a uniform, low-maintenance, water-wise carpet of green foliage with seasonal white-and-red flowers. It is particularly effective in rockeries, fynbos-style gardens, and as edging along paths.
Sources and Further Reading
ASPCA Animal Poison Control — Jade Plant. aspca.org
Plants of the World Online (POWO), Royal Botanic Gardens, Kew — Crassula undulata Haw. powo.science.kew.org
South African National Biodiversity Institute (SANBI), PlantZAfrica — Crassula dejecta. Notten, A. (2008). pza.sanbi.org
Tölken, H.R. (1985). Crassulaceae. In: Leistner, O.A. (ed.), Flora of Southern Africa, Vol. 14. Botanical Research Institute, Pretoria.
Eggli, U. (ed.) (2003). Illustrated Handbook of Succulent Plants: Crassulaceae. Springer, Berlin.
Rowley, G.D. (2003). Crassula: A Grower’s Guide. Cactus & Co. Libri, Venegono Superiore.
Stearn, W.T. (1992). Botanical Latin. 4th edition. David & Charles, Newton Abbot.