Lachenalia sargeantii is a striking, early summer-flowering plant with pendulous, tubular ivory blooms marked with apple-green, bright pinkish magenta and deep brown. It is only seen in flower following wild fires and the bulbs are adapted to remain dormant for years or even decades until favourable conditions prevail.
Lachenalia sargeantii is a deciduous, winter-growing geophyte (a plant with a subterranean storage organ) with a globose white bulb surrounded by several layers of hard, dark brown outer tunics. The bulb produces a ring of bulblets at its base and has fleshy contractile roots that pull it deeply into the soil.
Two long, linear, spreading leaves are produced from autumn to early summer, and are deeply channelled, with prominent maroon margins.
The erect, rigid scape (flower stem) is conspicuously deep maroonish purple and the pendulous, tubular, ivory flowers are arranged alternately along the upper portion or grouped together at its apex on long magenta pedicels (flower stalks). The three outer and three inner tepals each have a large green or brown swelling at their tips, and the inner tepals protrude well beyond the outer tepals.
The ripe fruit is a capsule shaped like an inverted egg, and the round, matt black seeds have a rough seed coat with a cobblestone-like surface texture.
Lachenalia sargeantii is a protected species. Its conservation status has previously been categorized as Insufficiently Known due to a lack of information, but owing to the discovery of additional large populations in 2005 and 2006, it is not considered threatened any longer.
Distribution and habitat
Lachenalia sargeantii is restricted to mountainsides in the southern Cape near Bredasdorp. It occurs in small groups, or as solitary individuals within large colonies on well-drained, stony, north-facing acid sandstone ridges, in open aspects or wedged between sandstone boulders. The plants are subject to harsh northwesterly winds in winter, and to baking heat during their summer rest period.
Derivation of name and historical aspects
The genus Lachenalia was established in 1784 and commemorates Werner de Lachenal (1739-1800), professor of botany and anatomy at the University of Basel, Switzerland. Lachenalia sargeantii was discovered in November 1970 by Robert Scott, a young visitor from New Zealand, while exploring a mountain near Bredasdorp following a large fire there the previous summer. He took a few specimens to the Cape Town resident Percy Sargeant, an experienced mountaineer, conservationist and photographer of high altitude flora, who in turn took them to Miss W.F. Barker, the authority on the genus Lachenalia, who recognized the flowers as unknown to science. She later named the species after Percy Sargeant in recognition of his contribution to nature conservation in the Western Cape.
There are approximately 120 species in Lachenalia and the genus is concentrated in the southwestern Cape, occurring in an arc from southwestern Namibia to the northeastern part of the Eastern Cape. Some of its most showy members include the tubular-flowered, bright red L. bulbifera, the orange, yellow or multicoloured L. aloides, and the speckled pink L. rubida.
Lachenalia sargeantii is a true pyrophyte, only flowering and producing leaves in the wild in response to wild fires of the previous summer or autumn, although in exceptional circumstances, a few inflorescences may appear in the second summer season following a fire. The bulbs are deep-seated, which is probably an adaptive strategy to escape damage from very severe fires. Even though sufficient autumn and winter rains may fall, the bulbs remain completely dormant throughout their winter growing period in the absence of a fire the previous summer or autumn.
The flowers are visited by the common orange and brown Painted Lady butterfly, Vanessa cardui.
Uses and cultural aspects
Once a successful technique has been developed to induce Lachenalia sargeantii to flower in cultivation, it could become a desirable pot subject.
Growing Lachenalia sargeantii
Although Lachenalia sargeantii is extremely rare in cultivation, it is an easily grown species. It produces leaves reliably every year and the bulbs multiply, but unfortunately the bulbs do not flower. Smoke-treating the bulbs in the nursery at Kirstenbosch has not induced flowering so far, but treatment of the growing medium surface with burning fynbos material may prove successful, for which purpose the bulbs are best grown in deep terracotta pots.
Place the pots where they will receive morning sun and afternoon shade, or alternatively bright light for as much of the day as possible. The plants require an extremely well-drained acid, sandy growing medium, such as three parts coarse river sand mixed with one part finely milled acid bark, or finely sifted acid compost.
Plant the bulbs in mid-autumn at a depth of 15-20 mm and water well. Once the leaves have appeared, apply a heavy drench approximately once per week until late spring, then allow the growing medium to dry out completely until the following autumn.
Sow the seeds in mid-autumn in pots or deep seed trays, in the same medium recommended for adult bulbs, with a 2-3 mm layer of river sand placed over the seeds, and keep moist using a watering can with a fine rose.
The bulbs are extremely sensitive to over-watering during their summer dormant period, and cannot be grown under general garden conditions where summer irrigation is carried out. The bulbs and leaf bases are susceptible to attack by the universal mealy bug scourge.
References and further reading
- Duncan, G.D. 1988. The Lachenalia handbook. Annals of Kirstenbosch Botanic Gardens 17. National Botanic Gardens of South Africa, Cape Town.
- Duncan, G.D. & Edwards, T.J. 2005. Lachenalia sargeantii. Curtis's Botanical Magazine 22: 176-184.
- Duncan, G.D., McMaster, C.J. & McMaster R.M. 2005. Out of the ashes. Veld & Flora 91: 66-69.
Kirstenbosch National Botanical Garden