Plant of the week: Orothamnus zeyheri

by | May 6, 2016 | Featured Slider, Latest, News

Orothamnus zeyheri Pappe ex Hook.f.

Family: Proteaceae

Common names: marsh rose, mountain rose (Eng.); vleiroos, bergroos (Afr.)

This is a slender, single stemmed, exquisite and rare fynbos shrub with exceptionally lovely, drooping rosy-red flowerheads borne in spring to summer.

 

Description

A tall, erect, sparsely branched shrub, 2–4 m in height, single-stemmed at the base. Leaves egg-shaped, 30–50 mm long, 20–30 mm wide, overlapping like tiles (imbricate), covered with long hairs, margin hairy, and with a smell like freshly ironed washing.

Orothamnus zeyheri foliage

Flowerhead terminal, axillary, 40–65 mm long, 40–60 mm across, drooping on a short, downwardly curved stalk. Involucral bracts ovate, 20–40 mm long, 20–40 mm wide, hairy, arranged in 4 or 5 whorls, pink to red. The flowerhead is made up of 20–45 yelow flowers, hidden inside the involucral bracts with only the tips visible. Perianth tube very short, segments otherwise free. The flowerhead is a curious contradiction in that the petal-like bracts, which are softly folded around one another like the petals of a rose, have a waxy translucent texture, yet the outer surface is covered with soft white hairs that form a fringe at the tips. Flowering occurs in spring to early summer (September–November).

Orothamnus zeyheri (Tony Rebelo)

Conservation Status

The conservation status of Orothamnus zeyheri is Vulnerable (VU). In 1980 this plant was considered to be facing a very high risk of extinction and was listed as Endangered (E). In 1996, it was assessed as Rare (R) because it has a restricted range, is a habitat specialist with a small area of occupancy and has a small total population with small subpopulations, but was not considered to be threatened at the time. Since 2006 it is considered to be Vulnerable (VU), which means that it faces a high risk of extinction in the wild.

The current assessment is based on the fact that there are 6 small, severely fragmented subpopulations occupying a total area of 23 km2 in an area of 196 km2. Wild flower harvesting and too-frequent fires in the past, have caused extensive population declines. Inappropriate fire management and the plant’s susceptibility to the root rot fungus Phytophthora, as well as baboons eating seeds and damage to plants by vlei rats, are causing a continued decline in numbers. Extreme population fluctuations have been observed, with subpopulation sizes varying from 10 to 1 000 individuals. The total population never exceeds a few thousand mature individuals and can drop to as low as a few hundred. These extreme fluctuations are mainly related to fire.

The factors that threaten the future survival of the marsh rose are wild flower harvesting, degradation of its habitat caused by human disturbance and changes in native species dynamics.

Orothamnus zeyheri was listed on Appendix I of CITES to stop the indiscriminate picking of wild flowers for the cutflower market. In 1997, it was downlisted to Appendix II, and in 2009, it was delisted from Appendix II. Strict controls imposed by the Department of Forestry and maintained by CapeNature have ensured that no harvesting from the wild takes place, nor is likely to occur in the future. Illegal trade in this species has not been recorded since 1981. All known populations fall within conservation areas and the plants are strictly protected.

In habitat, in the Kogelberg Mountains (Peter Slingsby)

Distribution and habitat

This species is known from two areas in the Western Cape in South Africa. The populations occur in the peaks of Kogelberg Mountains, which lie in the southern portion of the Hottentots Holland range, and a single small population on the Klein River Mountains near Hermanus, 40 km to the east. There is no certainty on whether the Klein Rivier Mountain population is natural or was as a result of a reintroduction. Orothamnus zeyheri grows in peaty seeps and swamps on moist, middle to upper slopes at 450–850 m altitude, and is largely confined to Kogelberg Sandstone Fynbos.

Derivation of name and historical aspects

Orothamnus is derived from Greek, oros, meaning ‘mountain’ and thamnos, meaning ‘bush’. The species was named after the botanist Karl Ludwig Phillip Zeyher (1799–1858). He was a German plant and insect collector, who collected extensively in South Africa. He was the author, with Christian Friedrich Ecklon, of Enumeratio plantarum Africae australis (1835–7), a descriptive catalogue of South African plants.

Orothamnus zeyheri was named by Dr Ludwig Pappe in 1848. Pappe (1803–1862) was a German physician and botanist who relocated to Cape Town in 1831, and became the first professor of botany at the South African College in 1858. It was first represented in an illustration by Jean Villet, a Capetonian artist and dealer in natural history specimens, which was featured in Curtis’s Botanical Magazine in 1848, volume 74, plate 4357.

The first plant of Orothamnus zeyheri was collected from an unknown locality in the Hottentots Holland Mountains by Zeyher in the 1840s, and there were no additional records until 60 years later, when plants were purchased from a roadside flower seller in Cape Town. The population on the Klein River Mountains was first discovered by botanists in 1907, and the Kogelberg population was only located in 1920. As a cut flower this plant has exceptionally lasting qualities in the vase, the inflorescence will keep perfectly for over a month. It was heavily picked by flower traders who sold their produce in the flower market for 200 years until the picking of wild flowers was restricted by permit system after the Second World War (1939–1945). The trade in the flowerheads on the flower market resulted in plant pickers picking many flowerheads of this plant over the years, which caused the population of the plant to be reduced.

In 1968 Charlie Boucher became interested in the plight of the marsh rose. He located and monitored the few remaining populations, and instigated an emergency program to try to save the species. He noticed that the healthiest populations were in areas where fire was not excluded, and also undertook trials with burning and hoeing, in order to find out which resulted in the best regeneration and healthiest plants. He showed that Orothamnus zeyheri needed fire at suitable intervals in order to regenerate, that summer burns were far better than winter burns, and that hoeing resulted in good germination, but poor survival of seedlings. In order to protect the plants, the reserve where they occurred was closed to the public, the plants fenced off and the area closely monitored. The reserve has since been opened, but access to the area is still strictly controlled and the area monitored, and strong viable wild populations continue to exist.

The genus Orothamnus contains only one species. It is most closely allied to the tube pagodas, Mimetes hirtus, M. pauciflorus, M. palustris and M. capitulatus, its flowerheads equivalent to the headlets of Mimetes.

Orothamnus zeyheri

Ecology

The plants are short-lived with an average of lifespan of ten years and a maximum of twenty years, and are killed by fire. In populations that are not burned for many years, the plants become moribund and die, and the population appears to be extinct. After a fire, seedlings come up in large numbers and the population will re-establish. Flowering commences after 3 years, reaching its peak after 9 years and after twenty years, most of the population will be senescent and near death. This is the stage that fire is needed to initiate a new regeneration cycle.

If fires are infrequent plants become moribund and die with no regeneration of young plants from seed. If the area is burned, in summer, every 15–20 years, there is usually good regeneration with lots of seedlings coming up. However, fires that happen too frequently have a negative effect on the species, as it kills all the plants before they have time to set seed, thus reducing the soil-stored seed bank.

The agent or agents of pollination are not known. The seeds are released a few months after flowering and are dispersed by ants. The ands are attracted by the oily elaiosome on the seed, carry the seeds back to their nests where they consume the elaiosome, but the seed remains unharmed and is safely stored underground. The seeds are long lived and remain viable for over 35 years below ground, and need summer fires to germinate.

As an Orothamnus zeyheri plant gets older the leaves on the lower portion of the stem die and fall off. If a stem is cut in the bare, leafless region, below the living leaves, that stem will not send out any new shoots, as it does not have buds where there are no green leaves. This is why the wild-flower harvesting took such a heavy toll on the wild populations. Many plants, and in some cases whole populations, were killed where all the flowers were cut. Wild flower harvesting also drastically reduced the number of seeds produced.

Uses

Orothamnus zeyheri was a popular cutflower until the 1940s when selling them was prohibited. It is not widely known or grown as a garden plant because it is difficult in cultivation, but specialist nurseries have successfully propagated it and plants in pots are now sometimes seen for sale in nurseries.

 

Growing Orothamnus zeyheri

In the wild, Orothamnus zeyheri grows on very steep, cool, south-facing slopes at altitudes of 450–850 m, in well-drained, peaty, spongy soil, through which moisture seeps slowly. It is also exposed to the sea winds and the mist and clouds brought in by the Cape’s notorious ‘South Easter’ wind that condenses and releases moisture on the plants during the summer months. It is difficult to mimic this habitat in most gardens and it has proved difficult to nearly impossible to maintain this species in cultivation at Kirstenbosch National Botanical Garden. It is very susceptible to the root rot fungusPhytophthora and to trampling or any disturbance, such as digging, around its base. At Kirstenbosch it is grafted onto the more resilient Leucospermum conocarpodendron rootstock, which has greatly extended their lifespan in the nursery.

In a garden situation, it is better to plant them in soil free from Phytophthora (nearly impossible in Cape Town area), and somewhere where they will not be disturbed, at all, and where they will not receive any overhead irrigation in summer, which leads to fungal problems and death of the plant. It would be preferable to allow water to seep past the plant, as it would in its natural habitat, but it will not tolerate soggy soil. It needs a cool spot with some air circulation and protection from excessive heat. It is also suitable for containers, and where Phytophthora occurs in the garden soil, a container is preferable. Orothamnus zeyheri is short lived, and if it survives the garden pathogens it will not live much beyond 8–10 years.

Orothamnus zeyheri can be propagated by seed and cuttings.

Seed set can be quite poor where there are few plants in flower, since they are self-infertile and need to be crossed in order to set viable seed. When cross pollinated by hand or in large populations, the seed set is good, up to 18 seeds per flowerhead. Sow seeds in well-drained, acidic, sterilized soil in autumn. Treat with smoke or the Kirstenbosch Instant Smoke Plus Seed Primer, before sowing. Treat the trays with a suitable fungicide to prevent damping off. Keep moist but not wet, and place in a cool well-aerated greenhouse. Rats are known to eat the seeds.

Cuttings are easily harvested, but if not treated against shock, they die easily. It can also be multiplied by grafting, which if done correctly and at the right time, is a huge success. Grafting should be done in late summer to early autumn, before they start flowering. Rind graft is most successfully done on Leucospermum ‘Veldfire’ (a hybrid between L.conocarpodendron and L. glabrum) which has resistance to Phytopthora and nematodes that attack the roots. The stem diameter of the scion and rootstock must be the same, and splice or wedge grafting can be done. After-graft care is very important and adventitious roots must be nipped off as soon as they appear, as they will weaken the scion quickly.

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