More than might ever meet the eye

The hyacinth bulbs of Krantzkloof

 

Text and photographs Neil Crouch

What, you might ask, do flowering plants have to do with eyesight, other than presenting visually attractive flowers to the pollinators on which they rely for successful seed set? Well, one plant family represented in Krantzkloof is of particular interest when it comes to sight, and human sight at it turns out. They are the hyacinth family, which through an international science collaboration, are being explored as a potential source of new drugs to treat the incurable eye condition known as wet age-related macular degeneration (AMD). Various small molecules known as homoisoflavanoids, isolated from the bulbs of one particular subfamily in the Hyacinthaceae, are being actively investigated for their anti-angiogenic activity (i.e. their capacity to keep new blood vessels from forming, in this case within the eye). This is to determine whether extracts can be developed as eyedrop therapy for this dreaded degenerative condition, which currently is treated by injections directly into the eyeball. Such anti-vascular endothelial growth factor (anti-VEGF) drugs block the production of VEGF, which is a protein that promotes the new blood vessel formation that results in AMD. As one might imagine, an eye drop alternative therapy would be most welcomed by all afflicted! That said, any AMD drug safely developed from the Hyacinthaceae will take many years yet to reach market – if ever ؘ– and readers are strongly advised against introducing such plant extracts into their eye. This is as many family members are toxic, and their sap corrosive in character, exampled by one Mediterranean species used in antiquity as a rat poison, and another local species being used as a homicidal agent.

This article looks at a variety of species from the Hyacinthaceae of Krantzkloof, yet considers only about half of the diversity that one encounters there. If there is one constant about this group of bulbous plants, it is that they are both a beautiful and mysterious bunch. Much taxonomic work is still required in South Africa on, particularly, the subfamily Hyacinthoideae, with the genus arrangements for both the subfamilies Urgineoideae and the Ornithogaloideae recently well resolved by an international group of collaborators based principally in Spain and Austria. The Hyacinthaceae is a very widespread family comprising four subfamilies and about 1000 species unequally shared between about 100 genera, with centres of diversity in southern Africa and the Mediterranean region, although diverse representatives are also found throughout Africa, as well as in South America and western Asia. In southern Africa, three of these four subfamilies (Ornithogaloideae, Hyacinthoideae and Urgineoideae) occur, and are richly represented by such well-known gardening subjects as chincherinchees, galtonias and pineapple lilies. All members of Hyacinthaceae possess bulbs, usually positioned below the soil surface, and most species are at least seasonally deciduous, bearing their strap-like or lace-like leaves either whilst flowering, or between their flowering periods. Most of the Krantzkloof species are inhabitants of the rocky grassland rim of the gorge, with some venturing onto the faces of the near-vertical cliffs. A further but less diverse set is encountered in the kloof forest, oft-times on rocky surfaces scattered below the shade of trees. This article introduces only several members of the family Hyacinthaceae, to highlight their beauty and diversity. Perhaps, for local readers, the most familiar of the local subfamilies will be the Hyacinthoideae, which as a subset is the most heavily sought-after and harvested for traditional medicine in KwaZulu-Natal. In Krantzkloof the most notable Zulu medicinal species in this group are in the genera Merwilla (blue squills) and Eucomis (pineapple flowers), many an extracted bulb of which will have made its way to the local muthi markets.

Merwilla plumbea

In spring the flowering stalks of M. plumbea project laterally from the cliffside, sporting numerous purplish-blue star flowers. Not every genus in the Hyacinthaceae has sky blue flower stalks, a feature seen here in Merwilla. Previously known as Scilla natalensis, this particularly variable species is found in Krantzkloof on sunny krantz edges and the ledges protruding from vertical rock faces.

Looking down over the edge of the upper Nkutu Gorge, plants of M. plumbea are seen growing in soil pockets on ledges. Their broad sword-shaped leaves are more extensively developed in mid-summer than when the plants flower in spring.

The tall inflorescences of M. plumbea are set with hundreds of flowers, seen visited here by a Painted Lady butterfly (Vanessa cardui) at a site near Harrismith.

Merwilla kraussii

Merwilla kraussii is another variable species in the genus Merwilla, but in this case we at least know this Krantzkloof form is ‘’true to type’’, for the original specimen linked to this name was, quite remarkably, actually collected in Krantzkloof. This was in 1840, by Christian Ferdinand von Krauss, a commercial German plant collector whose extensive gatherings from South Africa are today deposited in a wide range of European herbaria. The species he discovered was subsequently named for him, as one can reasonably deduce. At Krantzkloof M. kraussii has much narrower strap-like leaves and shorter, fewer-flowered and lighter-coloured inflorescences than are seen in M. plumbea, the other species found in this reserve. Krauss’s merwilla occurs in more open rocky sections of the Krantzkloof grasslands, rather than on the cliff faces to which the local M. plumbea plants are restricted.

As with other members of the genus Merwilla, the half-exposed bulbs of M. kraussii grow in tight clusters and present a tunic of characteristic light brown papery scales, shown here slightly singed by fire. The leaves are lightly hairy, quite unlike the local form of M. plumbea, the leaves of which lack hairs and are altogether more purple-infused.

The flowering stalks of M. kraussii are much shorter and fewer-flowered than those of M. plumbea; the inflorescences of both species present during late spring and early summer.

Schizocarphus nervosus

The erect broad leaves of Schizocarphus nervosus are characteristically tough and fibrous, and the flowering shoots distinctly broad, at Krantzkloof reaching about 12 cm in diameter at their base. Plants are found in short open grassland, often in small colonies.

The individual flowers of S. nervosus are borne on long pedicels, with each flower mostly white above and bearing distinctly clawed sepals that bend backwards as the flower ages. The ovaries of this species are a characteristic light charcoal-grey colour.

Ledebouria ovatifolia

Ledebouria ovatifolia is amongst the first of all grassland plants to flower each spring, producing several arching inflorescences, each of which bear many stalked purple-green flowers. The new season leaves typically only expand to their full dimensions once the flowering stalks have fully matured.

The widespread summer-rainfall species Ledebouria ovatifolia is extremely varied in both vegetative and floral form. What unites these diverse entities within a common species concept is, amongst other features, their broad egg-shaped and sometimes spotted leaves that press closely to the ground, and their purplish, fleshy outer bulb scales. These bulb scales have a distinctly squared-off (truncated) apex (Left) which, when broken, yield a quite copious quantity of fascinating elastic threads (Right).

Drimiopsis maculata

A species familiar to many gardeners in the summer rainfall region of South Africa, Drimiopsis maculata is better known for its spotted “stalked’’ leaves and its propensity for multiplying rapidly through bulb division, than it is for its non-showy flowers. A flowering colony is here shown alongside the Molweni River at the base of the kloof within the full shade of the forest.

Rather like the genus Albuca, the inner three tepals of flowers are erect and pressed close together whilst the outer three spread somewhat more; each tepal apex is characteristically hooded. Buds are white and the mature and spent flowers of Drimiopsis maculata green, to produce the bicoloured inflorescences with which many growers are so familiar.

Wasps of various types may often be seen visiting and one presumes pollinating the flowers of D. maculata. Here, what is likely a Tiphiid wasp is exploring an inflorescence; its left hind leg is resting on a fully open flower.

Boosia flagellaris

This, the Bootlace boosia, was first described in 2005 from material found growing at Krantzkloof, following its discovery by Rod Edwards, a local plant enthusiast. The species has since also been located at Inanda, Table Mountain near Pietermaritzburg, and along the eastern Illovo River. It occurs mainly on shaded moist cliffs within forest, and characteristically dangles its bootlace-like leaves and pipe-like inflorescences from the vertical rock faces. The specific epithet “flagellaris’’ refers to the whip-like leaves.

The angular and close-fitting bulbs of Boosia flagellaris are largely exposed above the vertical moist cliff cracks in which the colonies cluster.

Lit by a piercing shaft of light, the bright but short-lived flowers of Boosia flagellaris glow bright white within their forest setting.

Litanthus pusillus

Litanthus pusillus, one of the smallest of all members of the hyacinth family, has a particular requirement for shallow, well-drained soils overlying bedrock, always in full sun, where it forms large, albeit inconspicuous colonies. This species, one of only two in the genus, finds its home in Krantzkloof on the exposed sandstone shelves along the gorge edge. If you don’t especially look out for this diminutive bulb species you will likely not notice it, for the threadlike leaves shown here are only about 3 cm long and 0.3 mm in diameter.

The tiny tubular flowers of Litanthus pusillus are presented singly at the end of a short inflorescence stalk, from which they dangle vertically. They are only about 6 mm in length with the white corolla having a greenish-brown stripe towards the tube apex, and along its flared lobes. Such colouration is commonly seen in flowers belonging to the subfamily Urgineoideae, to which Litanthus belongs.

Urginavia echinostachya

A locally common inhabitant of the grasslands atop the Nkutu Gorge section of Krantzkloof, Urginavia echinostachya is easy to overlook, even when it flowers in spring, as the dull-coloured flowers are not obvious amongst the surrounding grass clumps.

The origin of the name “echinostachya’’ is not immediately clear, as this nomiker refers to a ‘prickly spike’, not exactly a great descriptor for this particular species. A portion of the inflorescence is shown here, to show the small, brown-banded and star-like flowers. This species was for long overlooked, and has only recently been identified for inclusion on the checklist of plant species that occur in KwaZulu-Natal. This happened after it was observed for sale in local muthi markets, which led to an investigation that linked it initially to a broad concept for Drimia cooperi, now known as Urginavia cooperi.

Although the characteristic salmon-coloured bulbs of U. echinostachya have quite loose and chunky scales (Left), each scale is exceedingly tough and difficult to tear due to the presence of numerous fibres (Right), their presence deemed a deterrent to herbivores such as mole rats and porcupines. Besides this mechanical approach to self-preservation, the bulbs of Urginavia species are well documented to produce bufadienolides, compounds toxic to mammals which have been shown to alter heartbeat rates and even cause heart attacks.

Drimia elata

Drimia elata is only occasionally encountered in Krantkloof, it being presumed that most specimens of this popular Zulu medicinal plants have long since been harvested from this site to supply the eThekwini muthi demand. This species is to be found in rocky sites, usually at the transition between grassland and cliff scrub habitats, or in clustered colonies overlying rock shelves at the gorge edge.

The silvery-purple tepals of D. elata flowers are characteristically fused at their base for about a third of their length and then strongly reflex to leave the erect stamens exposed and accessible to pollinators. Here a honeybee greedily grasps all six anthers, to gather pollen as reward for its visit.

Albuca setosa

Albuca setosa is a species which like so many other local Hyacinthaceae is diverse in its vegetative form; it essentially looks quite different wherever one encounters it! So named ‘setosa’ for the prickly projections that adorn the exposed top of the bulb, which are actually tough leaf veins that persist after the previous season’s leaves have died back.

The semi-succulent leaves of the Krantzkloof form of Albuca setosa are quite narrow, chanelled, and a blue-green colour.

The inflorescence of A. setosa is few-flowered, each bloom having white tepals with prominent green bands along the centre of their outside length. Characteristic of the genus Albuca, the inner three tepals are erect and press close together whilst the outer three spread outwards. Pollinators have been observed forcing their way between the upper three tepals to access the floral rewards, in the process effecting pollination and seed set.

Dipcadi viride

The widespread species Dipcadi viride is occasionally encountered in the grasslands of Krantzkloof, particularly towards the east of the reserve. The tall slender inflorescences that emerge from a tuft of grasslike leaves present all their plastic-looking flowers in much the same direction.

Within a single population of D. viride, up to three colour forms may be found growing together and flowering at the same time. This Krantzkloof form of D. viride lacks the prominent tails on the tepal tips that is often reported for this species.

Further reading

Crouch, N.R., Williams, V.L., Edwards, T.J. & Brueton, V.J. 2010. Hyacinthaceae. Drimia cooperi in KwaZulu-Natal, and the ethnomedicinal trade. Bothalia 40: 75-78.

Douwes, E., Crouch, N.R. & Symmonds, R. 2001. Blue squill in the red. Scilla natalensis as a conservation charge. PlantLife 24: 14-19.

Edwards, T.J., Crouch, N.R. & Styles, D. 2005. Drimia flagellaris (Hyacinthaceae), a new discovery from KwaZulu-Natal. South African Journal of Botany 71(1): 122-126.

Martínez-Azorín, M., Crespo, M.B. Alonso-Vargas, M.Á., Pinter, M., Crouch, N.R., Dold, A.P., Mucina, L., Pfosser, M. & Wetschnig, W. 2023. A generic monograph of the Hyacinthaceae subfamily Urgineoideae. Phytotaxa 610(1): 1-143. ISSN 1179-3155 (print edition) and ISSN 1179-3163 (online edition). https://doi.org/10.11646/phytotaxa.610.1.1

Martínez-Azorín, M., Crespo, M.B., Juan, A. & Fay, M.F. 2011. Molecular phylogenetics of subfamily Ornithogaloideae (Hyacinthaceae) based on nuclear and plastid DNA regions, including a new taxonomic arrangement. Annals of Botany (Oxford) 107: 1–37. https://doi.org/10.1093/aob/mcq207

Schwikkard, S., Whitmore, H., Sishtla, K., Sulaiman, R.S., Shetty, T., Basavarajappa, H.D., Waller, C., Frankemoelle, L., Alqhatani, A., Chapman, A., Crouch, N.R., Wetschnig, W., Knirsh, W., Andriantiiana, J., Mas-Claret, E., Langat, M.K., Mulholland, D. & Corson, T.W. 2019. The antiangiogenic activity of naturally-occurring and synthetic homoisoflavonoids from the Hyacinthaceae (sensu APGII). Journal of Natural Products 82(5): 1227-1239. http://dx.doi.org/10.1021/acs.jnatprod.8b00989

Author photo: Pat McKrill

About the author

Neil Crouch, a Kloof resident, has a Ph.D in botany from the University of Natal and works in the biodiversity economy field. He has authored numerous scientific papers and articles and co-authored Field Guide to Succulents in Southern Africa, and Ferns of Southern Africa: A comprehensive guide, both published by Struik Nature.