Polyxena corymbosa

(L.) Jessop
Family: Hyacinthaceae (Hyacinth family)

 

Polyxena corymbosa

Polyxena corymbosa is one of five members of a dwarf genus of brightly coloured, bulbous geophytes, most closely related to the endemic southern African genus Lachenalia. It is a strongly scented, autumn and early winter- flowering plant and its diminutive size makes it highly recommended for cultivation in containers and window boxes in sunny positions.

Distribution
It is restricted to the winter rainfall region of Western Cape, occurring in colonies on seasonally moist flats from the Olifants River Valley near Citrusdal to Somerset West and Gordon's Bay on the Cape Flats. Unfortunately it has become rare on the Cape Peninsula and the Cape Flats over the past few decades due to the development of roads, housing and industrial sites.

Ecology
P. corymbosa is a deciduous, winter-growing species, 50-100 mm high, that becomes completely dormant during the hot, dry summer, surviving the latter period by means of a soft, fleshy bulb. The bulbs respond rapidly to the first autumn rains, producing their dense flower clusters and several narrow, grass-like leaves more or less at the same time. The flowers are long-lasting (individual flowers last about 10 days), and are about 15 mm wide and 15 mm high. They are strongly honey-scented, and are pollinated by the common honey-bee, Apis mellifera. Like the other members of this genus, P. corymbosa has developed a remarkable seed dispersal mechanism, in which the subterranean portion of the peduncle (flower stem) elongates rapidly in late winter, just before the seed capsules split open. This has the effect of lifting the capsules into the air, which then bend over and fall to the ground a short distance away from the adult plants, releasing the seeds that can then be further dispersed by raindrops and wind.

Derivation of the name and historical aspects
The generic name Polyxena honours the Greek mythological figure of Polyxena, a daughter of Priam, the last King of Troy, and was established by the German botanist C.S. Kunth in 1843. The specific epithet corymbosa refers to the type of inflorescence this species has, i.e. a subcorymb, in which the flowers all bloom at more or less the same level. P. corymbosa has had quite a complicated taxonomic history and was well known by its former name Hyacinthus corymbosus. However, the genus Hyacinthus now only applies to the deliciously sweet-scented species from the Northern Hemisphere, including the numerous hyacinth cultivars we know and grow today as pot plants.

Uses and cultural aspects
P. corymbosa is not known to be used medicinally or culturally by the indigenous peoples of Western Cape.

Growing Polyxena corymbosa

The truly dwarf nature of P. corymbosa makes it exclusively the preserve of pot cultivation as the small fleshy bulbs resent any kind of soil disturbance such as that caused by surface-foraging runner moles. As the bulbs have a shallow root system, they can be cultivated in a wide variety of shallow containers. Place the pots in a sunny position or one that receives high light intensity for at least half the day. In the Southern Hemisphere, plastic pots are preferred over terracotta ones as the latter tend to dry out too rapidly. The plants are seen to best advantage massed closely together, and planted in a free-draining mix such as equal parts of coarse river sand and finely sifted compost or finely milled bark. Plant the bulbs in early autumn about 15 mm apart and about 10 mm deep. Water well and wait for the leaves to show, then water well once per week throughout the winter and early spring period, reducing water by the end of spring, and allowing the soil medium to dry out completely over summer. During the flowering period (late March to mid-May in the Southern Hemisphere), pots can be brought indoors where their brilliant flowers and strong sweet scent can be fully appreciated. P. corymbosa is not frost hardy and has to be grown in the cool greenhouse in cold climate countries of the Northern Hemisphere.

P. corymbosa is propagated by seeds sown in autumn, or by separation of offsets during the summer dormant period. Seeds can be sown directly into permanent containers, at a depth of about 2-3 mm, in the same medium recommended for adult bulbs. Be sure to sow the seeds thinly to prevent overcrowding, and keep the sowing medium moist by watering every few days with a fine spray. Germination of fresh seeds takes place within 3 weeks, and under ideal conditions, flowers may be produced for the first time during the second season of growth. The bulbs of P. corymbosa are long lasting and offsets form rapidly. When clumps become too thick and flowering performance diminishes, about every three to four years, the dormant bulbs can be lifted in summer and the offsets separated, and preferably replanted as soon as possible.

Like the other four Polyxena species, P. corymbosa is highly susceptible to infestation by mealy bugs that attack and multiply between the leaf bases and outer bulb tunics. Mealy bugs can transmit viral diseases from one plant to another, and are often spread by Argentine ants. Controlling ants goes a long way towards keeping P. corymbosa plants free from mealy bugs.

Reference

DUNCAN, G.D. 2003. Polyxenas. Veld & Flora 89: 22-26.

Author: Graham Duncan
Kirstenbosch National Botanical Garden
March 2003


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