Monilaria chrysoleuca (Schltr.) Schwantes
Common names: string of pearls, pea mesemb (Eng.); ertjievygie (Afr.)
An eye-catching succulent with unusual jointed stems that resemble a beaded necklace, and leaves that sparkle in sunlight.
Monilaria chrysoleuca is a deciduous, clump-forming shrublet that grows to a height of 200 mm. The stems are very distinctive, they are jointed and so resemble a beaded necklace. The species develops two types of leaf pairs during the growing season; a short and long leaf pair. The short leaf pair is the first to emerge at the beginning of the growing season, as they are hidden in the sheath during dormancy. The long leaf pair emerges later in the growing season and is elongated and cylindrical. This long leaf pair forms a sheath at the end of the growing season, so forming the characteristic jointed stem. Water-storage cells (bladder cells) are very conspicuous on the leaves and flowering stems and give the plants a glistening appearance.
The flowers are solitary and terminal, presented on peduncles, elevating them above the leaves, in autumn to winter. Flower are strongly scented and the petals (really modified staminodes) range in colours from white, yellow, orange, salmon, red to purple. The fruits are hygrochastic (water-responsive) capsules with 5 to 7 locules and covering membranes, but lacks closing bodies. The seeds are ovoid and smooth.
Although Monilaria chrysoleuca often has a small population size, these populations are relatively stable and the conservation status of the species is, therefore, assessed as Least Concern (LC) on the Red List of South African plants.
Distribution and habitat
Monilaria chrysoleuca is endemic to the Greater Cape Floristic Region of South Africa and its distribution extends from the Knersvlakte, just north of Vanryhnsdorp in the Western Cape, northwards to just east of Springbok at Nigramoep in the Northern Cape. The species is restricted to quartzitic flats with clay soils and grows in areas that receive full-sun exposure.
Derivation of name and historical aspects
The genus name Monilaria is derived from the Latin word monile, which translates to ‘necklace’ (of pearls) or ‘jewel’, referring to the distinctive structure of the stems which resemble a thick string of pearls. The specific epithet chrysoleuca is derived from the Latin words chryso, which means ‘golden’ and leuco, which means ‘white’, which may allude to the white and golden flowers of the species (although flower colour is variable in this species).
The species was originally described in 1899 by Schlechter, who included it in the genus Mesembryanthemum, but was transferred by Schwantes to Monilaria, in 1929. Prior to that, the species was also included in other Aizoaceae genera, including Conophyllum, Mitrophyllum and Schwantesia. The genus Monilaria currently includes 5 species after it was reduced from eleven species by Hans-Dieter Ihlenfeldt and Sigurd Jörgenson, in 1973. Monilaria is recovered in the most basal clade in the phylogeny of the most diverse tribe of Aizoaceae, the Ruschieae, and members of this clade are characterised by conspicuous papillae on the leaves and formation of a sheath during dormancy.
Monilaria chrysoleuca is associated with quartzitic flats, especially around the Knersvlakte, but also in Namaqualand. These quartzitic flats or patches are characteristic of the Knersvlakte and several of endemic genera from the Aizoaceae family are found on these patches. The seeds of Monilaria chrysoleuca are dispersed by capsules that open in response to moisture (hygrochastic), which is typical in the family. Once the capsule comes into contact with moisture, it opens to reveal the seeds, which are covered by a membrane. During a rainfall event, the raindrops expel the seeds by falling onto these membranes, which then shoots the seed out. In this way, the seeds are dispersed when conditions are favourable. This short-distance dispersal means that new seedlings do not travel far from the parent plant.
Monilaria chrysoleuca is deciduous, shedding its leaves at the end of the winter rainfall season, so that it is dormant during the hot and dry summer months. The flowers are strongly scented, opening at midday and closing in the late afternoon. The species flowers from autumn to winter (from May through to August in SA) but flowering time is relatively short and lasts only 3 weeks. The annual addition of a leaf pair to the stem makes it easy to estimate the age of the plant and it has been suggested that the plant itself lives remarkably long, possibly more than a century.
The main use of Monilaria chrysoleuca is an ornamental plant that is used to decorate gardens and homes. It is very popular among succulent collectors’, due to the conspicuous bladder cells on the leaf surface which sparkle when in the sun, as well as the large striking flowers. Currently, there is no known medicinal uses for this species.
Growing Monilaria chrysoleuca
As natural populations of Monilaria chrysoleuca are found on the highly-specific quartzitic soils of the Knersvlakte, the species is not as easy to grow as many other collectable succulents and require a moderate level of maintenance.
The cuttings of Monilaria chrysoleuca are difficult to root, so propagation is usually done from seed. The most efficient way to collect the seeds is to allow the capsules to dry on the plant. Once dry, break the capsules open and gather the seeds. The best time to sow the seed is in autumn. Monilaria chrysoleuca grows most successfully when potted in sandy, well-drained soils and placed in full-sun. Planting the seeds into a pot with sufficient drainage is very important as the species is known to be susceptible to root rot.
Restrict watering in summer, as the species naturally occur in winter rainfall areas and only once the new leaves appear in autumn, should you water regularly. Do not over-water the plants, as they are adapted to arid conditions. Possible pests of Monilaria chrysoleuca include mealy bug and scale on the leaves. Although plants of M. chrysoleuca go into dormancy during the summer months, the unusual stems are still striking and the grower is rewarded during the winter months with 2 leaf types, as well as a display of large flowers. M. chrysoleuca can be grown together in a large pot with a range of other succulent species, creating a year-round attractive pot.
- Burgoyne, P.M. 2006. Monilaria chrysoleuca (Schltr.) Schwantes. National Assessment: Red List of South African plants version 2017.1.
- Court, D. 1981. Succulent flora of southern Africa. Balkema, Cape Town.
- Hartmann, H.E. ed. 2002. Illustrated handbook of succulent plants: Aizoaceae F–Z (Vol. 2). Springer Science & Business Media, Berlin, Heidelberg, New York.
- Ihlenfeldt, H.D. & Jörgensen, S. 1973. Morphologie und Taxonomie der Guttung Monilaria (Schwantes) Schwantes s. str. (Mesembryanthemaceae). Mitteilungen aus dem Institut für Allegemeine Botanik, Hamburg 14: 49–94.
- Klak, C., Bruyns, P.V. & Hanáček, P. 2013. A phylogenetic hypothesis for the recently diversified Ruschieae (Aizoaceae) in southern Africa. Molecular phylogenetics and evolution 69: 1005–1020.
- Smith, G.F., Chesselet, P., Van Jaarsveld, E.J., Hartmann, H., Hammer, S., Van Wyk, B-E., Burgoyne, P., Klak, C. & Kurzweil, H. 1998. Mesembs of the world. Briza, Pretoria.
Stephany van Munster and Robyn F. Powell
Plant Type: Shrub, Succulent
SA Distribution: Northern Cape, Western Cape
Soil type: Sandy
Flowering season: Autumn, Winter
Flower colour: Purple, Red, White, Yellow, Orange
Aspect: Full Sun
Gardening skill: Average