Photographs by Connall Oosterbroek.
SOME SCARCE AND ORNAMENTAL BULBOUS PLANTS FROM SOUTH AFRICA AND SOUTH WESTERN NAMIBIA.
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 Details of the dwarf Brunsvigia namaquana flowers shortly after they have opened. The pollen grains are ripe and ready for harvesting on a cotton bud used for manual cross pollination. |
 Brunsvigia namaquana flowers freshly opened and an unopened bud alongside. This photograph shows clearly the diminutive size of these plants. |
 A bud of the new Brunsvigia species from the Pellaberg photographed a few days before the flowers started to open. |
SUMMARY
Two dwarf Brunsvigia species found in the Northern Cape are discussed in this newsletter. One, Brunsvigia namaquana is found in the arid western foothills of the Khamiesberg and the other occurs on the Pellaberg and some other mountains to the west. The most densely pubescent forms of Haemanthus humilis subspecies hirsutus are associated with dolomite hills or mountains. They are generally rather rare and absent from much suitable habitat.
Strumaria barberae is a beautiful species found growing on the Huib Hoch Plateau in south western Namibia. It has amongst the most ornamental of all flowers in the genus.
The natural occurrence, propagation and cultivation of all these plants is discussed in the newsletter. They all make for ornamental and rewarding pot plants.
NEWSLETTER
AN ACCOUNT OF HAEMANTHUS HUMILIS SUBSPECIES HIRSUTUS IN HABITAT ON DOLOMITE FORMATIONS
Haemanthus humilis subspecies hirsutus is a widespread species in the summer rainfall area of South Africa and very variable in leaf. The leaves may be moderately or densely covered in hairs or bristles and hairy on both the upper and lower sides of the leaves or else only on one side.
The subspecies associated with dolomite formations is often the most attractive. The leaves are covered in long silky white hairs that vary between 5 and 10 mm in length. This form occurring on dolomite is seldom recorded. It is also absent from many limestone areas that lie within the distribution range of the subspecies. Plants have been recorded from the Highland Mountains near Makopane (formerly Potgietersrus). These colonies are found on the property of the Klipspringer Diamond Mine and are situated on the south and east-facing ledges of low dolomite cliffs. They also occur amongst rough tumbled rocks. The sunnier flatter aspects above where the Haemanthus grow are home to a large number of Euphorbia restricta at the westernmost end of its distribution range. Access to the diamond mine is strictly controlled and for all practical purposes this plant and other rarities are difficult to study here.
Equally large numbers of the subspecies grow in a small area of the Skurweberg, a broken range of large dolomite hills north of the city of Johannesburg. The plants here also grow in fissures of low dolomite cliffs. They are particularly beautiful, and fresh leaves emerge in late January, covered in long silky white hairs.
The subspecies associated with dolomites has a number of differences from plants generally classified under the existing concept of Haemanthus humilis subspecies hirsutus. The new leaves emerge very late in the summer, sometimes only in mid- February. The seeds are also very much smaller than those observed on other plants presently assigned to the subspecies concept. It may be that the status of the subspecies associated with dolomites is in need of further study. At present these Haemanthus can only be regarded as rare and little known.
BRUNSVIGIA NAMAQUANA IN THE ARID EASTERN FOOTHILLS OF THE KHAMIESBERG, NAMAQUALAND
Brunsvigia namaquana is the smallest species in the genus. It has a limited distribution mainly in the eastern foothills of the Khamiesberg near Rooipoort. This is a rain shadow area receiving scant precipitation in the winter months from May – September. Occasional late summer thundershowers at the extreme western boundary of Bushmanland may drench the habitat. The bulbs send up buds shortly after receiving late summer rains and flowering and seeding is completed rapidly usually within a month.
The bulbs occur gregariously in sandy depressions on rocky outcrops. These places retain moisture for longest after rainfall and are conducive to the germination of seeds. This species in common with most Brunsvigias have an umbel which detaches from the bulbs when the seeds are ripe allowing it to be blown about in the wind dispersing seeds as it tumbles around. The small umbels are only about 5 x 5 cms wide and the seeds are very small only 2 – 3 mm in diameter. Successful germination depends largely on the habitat receiving sufficient moisture soon after the seeds are set. Some places are covered in the Brunsvigias usually where there are deep sand patches littered with rock fragments which prevents the habitat from drying out too quickly after rain.
The foliage is very distinctive a dull olive green with numerous stiff golden hairs. The leaves of Brunsvigia radula are similar but larger and rounded. They are also covered in pustules each bearing a short stiff ivory coloured bristle. B. radula also occurs on shady south and south west-facing slopes generally in much wetter places than B. namaquana which grows in sandy depressions on barren rock outcrops exposed to day-long sunlight.
B. namaquana is associated with a rich geophytic and succulent flora. Small bulbs in several different genera occur round about. Amongst the succulents the red flowered Avonia alstonii is common and the type locality of Lithops naureeniae is less than a kilometre away from a large colony of the Brunsvigias. It may be that B. namaquana is better represented than the paucity of records indicates. The habitats frequented by the plants are rather remote and rugged, often well away from roads or tracks making exploration difficult.
A NEW BRUNSVIGIA SPECIES FROM THE PELLABERG
The Pellaberg is a colossal mountain that runs in an east west direction and is situated close to the Orange River. The Brunsvigia is found throughout the Pellaberg on south, south east and south west-facing slopes. These beautiful dwarf plants are well distributed on the mountain west of the small town of Pella. They throng rocky slopes growing at the edges of colossal white huge boulders and on rocky ledges with deep soil. Closely packed groups of these plants are often wedged into rocky fissures.
The bulbs respond to late summer and early autumn rains which may at times be so heavy that gravel roads in the area are washed away. Good precipitation such as this keeps the seepage areas and shady slopes of the mountain moist for months after the rains have fallen. At these times the Brunsvigias flower in large numbers with swathes of white and pale pink flowers visible all up the slopes. In seasons when the late summer and autumn rains fail the bulbs remain dormant but sprout leaves if rain falls in winter. The winter rainfall consists of the remnants of moisture swept in by cold fronts that originate in the south Atlantic. Several years may pass in succession with little or no rainfall and during these dry spells the Brunsvigias remain dormant.
The flowers of this very ornamental species are large and showy. They are generally white when they first open but this changes to pale pink after a few days. The plants have been well known to amateur and professional botanists for some time and are also known from other mountains such as the Gamsberg to the south west of the Pellaberg. The furthest east the plants have been recorded is the ridge immediately north of Pofadder. This is in effect an eastern extension of the Groot Pellaberg.
STRUMARIA BARBERAE, THE JEWEL OF THE HUIB HOCH PLATEAU
The Huib Hoch Plateau is a prominent chain of large flat-topped limestone hills in south western Namibia that reaches 1800 metres at its highest point in the north and lies at an altitude of about 1200 metres in the south. In the north the plants occur in various places on the farm Aar and on the south central part of the plateau they are found on the farm Kliphoek. The bulbs grow in clayey soils littered with black limestone chips amongst the calcrete rock fragments.
The Strumarias flower in March and April if there are autumn thundershowers at this time. Should the rains fail they remain dormant. Flowering and seed set in cultivation usually takes 4 – 5 weeks and this pattern is likely to be similar in habitat though there is currently no data concerning the flowering and seeding habits in the natural populations. The bulbs are sometimes densely distributed in places, usually in areas with the deepest soils.
In habitat the leaves emerge shortly after flowering and persist throughout the autumn and winter months shrivelling in spring as the weather warms up. Cold fronts in the winter months bring some rain and this may be regular and good in some seasons. The autumn and winter rains sometimes fail and at these times the Strumarias remain fully dormant. There is also a minimum amount of rain that needs to fall in habitat during March or April to stimulate flowering. Sufficient moisture needs to saturate the soil which, as it is calcrete clay, holds moisture for a long time.
At the southern end of the distribution range the plants occur in close proximity to Strumaria hardyana a south western Namibia endemic. S. hardyana is at the north eastern boundary of its distribution range where it occurs on the farm Kliphoek. Its habitat here is amongst black limestone rocks in deep soil filled fissures on low cliffs. This habitat does not overlap with that of S. barberae but both species flower in March and April.
The rainfall in south western Namibia is not only erratic in the autumn months but also unpredictable as to where it will fall. In the autumn of 2004 for example the D727, the road north east of Rosh Pinah, was washed away in many places where it passed over the Huib Hoch Plateau. At the north end of the plateau however hardly any rain had fallen and the little that had, on the farm Aar, was insufficient to bring the Strumarias into flower.
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A close-up photograph revealing the details of Strumaria barberae flowers and buds. The elegant blooms are sometimes flushed with shell pink. |
CULTIVATION
The two Brunsvigia species are grown in a gravelly sandy mixture under cultivated conditions in Johannesburg. The pots are exposed to strong direct sunlight throughout the year and the plants watered from early February until August. At this time the leaves start to show signs of yellowing and the bulbs begin to enter their dormant phase. B. namaquana may flower if the pots are not watered in February but the undescribed species never does unless watered. Buds emerge from the soil about 5 – 8 days after the first good watering of the season and the flowers appear shortly afterwards.
The flowers of both Brunsvigia species are manually cross pollinated with cotton buds. The seed set in both instances is variable from one year to the next but always the best in any given season in the case of the Pellaberg species.
Haemanthus humilis subspecies hirsutus may be grown in containers or sunny well-drained beds where the soil is not disturbed, in summer rainfall regions of South Africa. The plants should be watered from about October until late March and kept dry during the winter months. Seeds may be produced by cross pollinating different flowers but seed set is usually variable from one season to the next. The subspecies associated with dolomites should be grown in a very well drained mixture. The Haemanthus thrive in places where there is lightly dappled shade or only morning sunlight.
Strumaria barberae grows very well in containers and does not seem too particular about its soil requirements. It is grown in very alkaline calcrete clayey soil in cultivation in Johannesburg and also a well-drained gritty mixture. The bulbs grow and flower well in both these mixtures which are really at opposite ends in the cultivation spectrum.
S. barberae is taken out of dormancy in late January and well watered. Buds usually emerge within a few days in cases where bulbs are going to flower in a given season and within two weeks they are in full bloom. The beautiful white trumpet-shaped flowers are manually cross pollinated at regular intervals throughout the flowering period. Seed set varies a great deal but is usually at its worst when the bulbs flower during periods of prolonged rainfall.
PROPAGATION
The Brunsvigia seeds are kept on tissue paper which lines shallow plastic trays. Shortly after they have sprouted a radicle they are planted out individually about 1.5 cms apart. The root is firmly buried in a hole pricked into the soil. The same method for sowing the seeds is used in the case of H. humilis subspecies hirsutus and S. barberae.
The seeds are sown in a well-drained gritty sandy mixture with no compost mixed in except for the Haemanthus. In this case a small amount of very well-rotted compost is added. The seedlings all thrive best in Johannesburg when exposed to rainfall. In order to protect the germinating seeds against heavy downpours fly screen netting is used to cover the pots. This breaks strong rainfall very effectively.
The seeds of all three species should be sown on the surface of the soil and only the root buried. Once the young plant has started to grow and the seed has withered the fly screen netting cover is removed and the young plants are capable of surviving heavy rains.
S. barberae is very slow to flower when grown from seeds, even under the ideal conditions supplied for cultivated plants. Seeds sown in February 2004 had produced strongly growing bulbs a few years later but none of them had flowered by February 2009 the beginning of the sixth growing and flowering season.
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