TWO RARE STRUMARIAS FROM SOUTH WESTERN NAMIBIA AND NERINE GIBSONII FROM THE NORTH EASTERN CAPE, SOUTH AFRICA.
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 A pink flowered Nerine gibsonii in its habitat west of Cala, photographed in late March 2008. |
 Strumaria hardyana flowers are produced just before the foliage, typically in early to mid April. |
 Nerine gibsonii has very attractive flowers that are often white or white tinged with shell pink. |
SUMMARY.
Four Strumaria species with ornamental fans of leaves produced in the autumn and winter growing season are found in the south western corner of Namibia. These are Strumaria hardyana, Strumaria phonolithica, Strumaria luteoloba and Strumaria speciosa. The account which follows concentrates on the natural occurrence and cultivation of S. hardyana and S. speciosa.
Nerine gibsonii is critically endangered in its degraded grassland habitat in the north eastern Cape in South Africa. There is a detailed discussion of the plants in their modern day environment followed by information concerning their cultivation and propagation.
NEWSLETTER.
The Strumarias of south western Namibia have adapted to an autumn and winter rainfall climate. Two species Strumaria phonolithica and Strumaria speciosa grow in places where they receive a good deal of moisture from fog. Heavy fogs, which occur on the mountains where these plants grow, precipitate as soft penetrating rain.
S. speciosa was described recently (Snijman 2005: 23 – 25) and is so far only known from the Sonnenberg, a high mountain south east of Rosh Pinah adjacent to the Orange River. This is a very remote and inaccessible area and it is possible that the plants may occur on surrounding peaks such as Koamsib to the north east and parts of the Namusberg to the north west.
S. hardyana was originally recorded as having a limited distribution from Spitskop just north of Rosh Pinah to Witputs. A recent record in May 2006 (Charles Craib) from Nooitgedacht indicates that the plants occur in the southern part of the Huib Hoch Plateau extending the known distribution range much further north east-wards. S. hardyana seems to be an entirely rainfall dependent species. Its distribution lies well out of the fog belts adjacent to the Atlantic Ocean or along the mountains fringing the Orange River, inland from the sea.
Nerine gibsonii currently occurs in a small area of the former Transkei near Cala in the North Eastern Cape. The plants are critically endangered by over-grazing and associated erosion of the grassland habitat as well as invasive Australian Black Wattles Acacia mearnsii which have destroyed most of the habitat available to the plants. There is presently some confusion (Craib in ed. 2008) as to the status of pink flowered N. gibsonii-like plants which occur between Indwe and Ugie in identical habitat to N. gibsonii. If these plants are classified as N. gibsonii the future of the species is more secure.
STRUMARIA HARDYANA.
Strumaria hardyana occupies three habitat niches. In the Spitskop area north of Rosh Pinah the bulbs grow on gently sloping south-facing rises at the bases of large hills. The plants here grow in scattered groups in areas with deep soil often littered with large rocks and cobbled with smaller pebbles. Near Witputs to the north the bulbs grow in dense concentrations at the bottom of seepage areas. These again are areas of deep soil often between large sheets of black exposed dolomite.
Another favoured site near Witputs and to the north east, on the south central Huib Hoch Plateau, are deep soil pockets in broad vertical cracks of low black limestone cliffs. The bulbs here are very deep-seated in the rocky fissures where they are protected from desiccation.
S. hardyana may remain dormant for several years in succession if the irregular autumn (late March, April) and winter (June – August) rains fail. Autumn rains are essential for the plants to flower and consequently good flowering is probably restricted to about once a decade. Winter rains cause the plants to come into leaf within a few days if there has been no autumn rainfall. If there has been autumn rain the bulbs automatically produce leaves in early to mid-May.
Seeds are liberated into the environment from early to mid-May. They have enough reserves to sprout roots and if there are further rains in the winter a good number of young bulbs will be recruited to the populations. If, in contrast, the winter rains fail few seedlings manage to survive.
The S. hardyana near Nooitgedacht on the Huib Hoch Plateau are very large and robust and may warrant recognition at subspecies or varietal level. They are certainly well separated from the bulbs that occur between Spitskop and Witputs.
S. hardyana is probably the best represented of the south western Namibia fan leaved Strumarias and it may be more widespread than present records indicate. It is certainly the most readily observed of these Strumaria species.
STRUMARIA SPECIOSA.
Strumaria speciosa grows on the summit of the Sonnenberg, a mountain adjacent to the Orange. The bulbs occur in a very narrow area which receives mountain fog mostly during the winter growing season. During a visit to the habitat in early August 2007 it was found that a heavy fog that was present a few days before had condensed as gentle rain leaving the soil and bases of the surrounding rocks quite moist.
The Strumarias occur in south and south-west-facing positions often with their large fans of leaves well exposed. The leaves may well play a role in condensing fog as the long bulb necks are often moist a few days after fog has swept over the mountain summit. In the area of the mountain that was studied the Strumarias were rather sparse, usually occurring singly and occasionally in scattered groups consisting of a few young plants and one or two large ones.
It would appear that the bulbs flower very erratically in nature as amongst the 40 or so large plants encountered, only a handful had the remains of the current season’s flower stems produced earlier in the winter. Very little is known at this time about the autecology of the species. It would seem that several successive years pass without any flowering as the sparse number of young bulbs that were noted in the habitat were roughly the same age.
The Strumarias are in shade for a good deal of the winter, only a few of them on the more elevated outcrops receiving about 40 – 120 minutes of direct sunlight. The majority of the bulbs, however, grow at the bases of cliffs and in these positions would remain shaded throughout the day. The bulbs share their habitat with several other apparently undescribed species including a Dipcadi with highly crisped leaves like Haemanthus crispus, and an Othonna with very large rounded succulent leaves like Tylecodon singularis for which it was originally mistaken. There is also a clump forming Tulbaghia species and Oxalis with large bicoloured silver and green leaves which also seems to be new.
The intriguing question remains as to whether S. speciosa grows on mountain peaks in the same general area of south western Namibia and whether or not its distribution extends across the Orange River into the northern parts of the Richtersveld in South Africa. A pointer to this possibility would be to observe the patterns of fog condensation on the surrounding mountain tops in Namibia and South Africa and to explore these places.
The upper part of the Sonnenberg has a distinctly greenish appearance when viewed from the vicinity of the Orange River. Mountain tops with a similar colour, standing out from the others which are brown and sere, would repay study.
NERINE GIBSONII.
Nerine gibsonii has some of the most attractive flowers of all the South African Nerine species. The plants are presently known from a small area near Cala in the former Transkei of the north eastern Cape. They used to occur in large numbers in a grassy valley with a stream flowing through the bottom. These depressions, known as vleis in South Africa, are a regular feature of much of the north eastern Cape, below the Drakensberg escarpment.
There are two serious problems facing the continued survival of N. gibsonii. The one is the severe degradation of the grassland habitat through excessive grazing by livestock. The other is invasion of huge amounts of the grassland habitat by invasive alien Black Wattles Acacia mearnsii. If these causal factors that are leading to the plants decline remain unchecked, extinction of this beautiful plant is certain during the course of this century.
A further matter that complicates the situation is the taxonomic status of the pink flowered Nerines that occur between Indwe and Elliot and between Elliot and Ugie. These plants have an identical autecology to that of N. gibsonii and many technical similarities with respect to floral morphology. They have at various times been referred to as Nerine appendiculata and N. gibsonii and there is at least one record in a South African herbarium that classifies the plants as N. gibsonii. This herbarium specimen is from a collection east of Ugie also in a grassy vlei. The question is probably best addressed in a revision of the Genus Nerine and the matter is more fully discussed in an article scheduled for publication in the September 2008 Veld and Flora, the journal of the Botanical Society in South Africa. (Please see below under further reading).
Two separate N. gibsonii colonies were visited near Cala in late February 2008. The 2008 flowering season was an excellent one for all the north eastern Cape Nerines. These had been abundant and regular rains in the latter part of the summer and the streams in the vleis had regularly burst their banks. This ensured optimum moist flowering conditions for the plants.
The well known vlei west of Cala had been heavily trampled but a small number of N. gibsonii were in flower. The stream which is now a wide eroded gulley contained Nerines flowering in clods of earth that had broken off from the banks. Although severely trampled there are large parts of the vlei that still have grass cover and are not eroded. These places may have many bulbs that never obtain the chance to flower and the situation could still be saved in the next few years were some management programme of the site be put in place.
Also near Cala another site was visited. This consists of a stream flowing through rocky grassland with a few small pockets of adjacent marshland. This locality, although only a few hundred square meters in size, had numerous N. gibsonii in flower densely utilising every available niche. The western end of the site was littered with rocks from blasting activities in a nearby borrow pit. Despite this some bulbs had still managed to flower between the rocks in what little habitat remained.
N. gibsonii in large grassy vleis has a bleak future but should there be further sites beside streams in rocky grassland, plants in these places may be more secure. Livestock has a preference for grazing in large vleis and open pastures avoiding rocky grasslands.
CULTIVATION OF THE STRUMARIAS.
STRUMARIA HARDYANA.
S. hardyana is readily cultivated in any well drained soil if grown in plastic pots. The plants thrive in earthenware containers and in these a more loamy soil mixture may be used. The bulbs are cultivated in dolomite derived loam in Johannesburg when they are grown in terracotta pots. This loam equates with that found in the dolomite soil on the black limestone mountains around Witputs in south western Namibia.
The plants are kept in direct sunlight during their autumn flowering season which is the second half of March in Johannesburg. They remain in these sunny places throughout the winter leafing season. Regular watering during the winter ensures that the leaves develop well and remain turgid. This species has to be kept in strong light in order to retain the characteristic fan of leaves that is so typical of wild plants.
In Johannesburg watering begins in the second half of March and the plants that are going to bloom in a particular season send up flower stems within a few days. The bulbs flower mostly during April and set seed in late April and early May. The berries are harvested at the time they are fully ripe and have a reddish colour. This is the time they detach easily from the withering inflorescences. Berries are stored on tissue paper placed on flat trays in a well ventilated room with plenty of light, but no direct sunlight. They usually sprout roots in late May and early June and are sown at this time. Each seed is individually sown with the root fully buried but the seed itself left exposed. Seeds are placed about 1.5 – 2 cms apart so that the young bulbs need not be disturbed and transplanted.
Bulbs usually reach maturity within 5 years when grown from seed. They may be fully mature with the characteristic fan of leaves in the autumn of their fifth year but many do not flower in cultivation in Johannesburg until a few years later.
As with all Strumaria species cross pollination using cotton buds results in good seed sets. For some unknown cause S. hardyana may not flower in cultivation for a few years in succession.
STRUMARIA SPECIOSA.
S. speciosa is difficult to grow completely true to character in cultivation. This species has the most spectacular fan of leaves of all the Strumarias, but if grown in the incorrect light conditions these etiolate and become untrue to character. In Johannesburg the plants are grown in conditions of strong light, but with only 2 hours of direct autumn and winter sunlight. The plants are grown in a south west-facing position with their terracotta pots raised up on top of a double layer of bricks to ensure free air circulation. Under these conditions the leaves develop perfectly identical to plants growing in their habitat on the Sonnenberg.
The bulbs are cultivated in dolerite derived loam between chips of dolomite rock. Pots 26 cms deep and 30 cms wide are used and the plants are deeply watered at about weekly intervals, except during the second half of June and July which is generally the coldest part of the winter in Johannesburg.
The plants are taken out of dormancy in late March and exposed to rainfall if there is rain about or otherwise watered with rainwater. Most of the bulbs sprout leaves within 5 – 7 days but occasionally the odd one may come into leaf about 3 – 4 weeks after watering commenced. The fan of leaves is usually fully developed within 2 – 3 weeks after they emerge. Young bulbs have 3 leaves whereas in older plants there are usually 4 and occasionally 5.
Temperatures in Johannesburg usually start to warm up in the second half of August as the day length increases. At this time the leaves gradually start to wither from the tips and the pots are put into dormancy. During dormancy the plants are kept in a raised well ventilated position in continual shade for the duration of the summer. They are kept bone dry.
CULTIVATION OF NERINE GIBSONII.
N. gibsonii is best cultivated in large deep pots about 22 cms tall and some 25 cms wide. They grow in most soils, but should the growing mixture be very porous the bulbs must be very well watered from January until the end of March which is the peak of the growing and flowering season. An ideal cultivation mix has been found to consist of half silt and half sandy soil to which a very small amount of humus has been added and very well mixed in.
The pots in which the Nerines are cultivated should be placed in direct sunlight for at least a full morning or a full afternoon. The bulbs seem to grow best when exposed to natural rainwater.
The species is readily propagated from seeds. Good results are usually achieved when seeds are allowed to form roots. The method used is the same as that described for the Strumarias. Seeds should be sown 1 – 1½ cms apart with the root sunk into holes made with a long thin twig. The seed itself should not be buried but left exposed on the surface of the soil.
The first young leaf sprouts after about a week followed often by a second 7 – 10 days later. In South Africa seeds are usually produced in February and the seedlings grow vigorously during March and April. Seedlings may continue to grow through the winter and only enter dormancy briefly the following spring. Should this happen the young bulbs are regularly watered throughout the winter. Heavy autumn thundershowers may be a problem in March in Johannesburg. As a result of this the seeds are covered with rust proof aluminium fly screen netting. This has the effect of breaking hard rainfall and few seeds or young bulbs are lost.
Seeds may also be lightly scattered across the surface of the soil as they start to sprout roots. These young roots quickly find their way into the ground. It is essential, however, to protect seeds sown in this manner from heavy rainfall with aluminium fly screen netting. An entire crop of seeds can be lost if this precaution is not taken when they are germinated in pots kept out in the open. Developing seedlings require at least half a day’s sunlight. This speeds up the development of the young bulbs.
FURTHER READING.
Craib, Charles. The Autecology and Status of Nerine gibsonii and its allies
in the North Eastern Cape (in ed.). Veld and Flora, September 2008.
Editor Caroline Voget. Email address: voget@kingsley.co.za
Craib, Charles. Strumaria hardyana in its habitat on the fringes of the Namib Desert in South Western Namibia. Herbertia, Volume 58, 2003 – 2004: 137 – 139.
Dold, Tony and McMaster, Cameron. Nerine gibsonii the exquisite Gibson’s Nerine, a species that could well be threatened with extinction. Veld and Flora, September 2004: 102 – 104.
REFERENCE.
Snijman D.A. Three new species and a new synonym in Strumaria (Amaryllidaceae: Amaryllideae) from Southern Africa. Bothalia Vol. 35, 1 May 2005: 21 – 27.
The pink flowered Nerine species that occurs between Indwe and Elliot and then eastwards to Ugie.
Nerine gibsonii photographed in their habitat west of Cala in late March 2008. There are very few plants visible in flower owing to trampling by livestock earlier in the growing season.
Photographs by Connall Oosterbroek and Tony Kietzman.