Download Angraecum longicalcar

Angraecum longicalcar
(Bosser) Senghas
Te x t b y E L S A H A L L
P.O. Box 802, George 6530. E-mail: [email protected]
Photography by RAQUEL DE CASTRO MAIA
Website: www.createphotography.co.za
Madagascar is recognized as one of the most ecologically
rich countries in the world with 80% of its flora
found nowhere else on earth.
Angraecum longicalcar: whole plant.
B
ut its magnificent plant life is
under threat. Habitat destruction and
over-collection mean that some rare
and beautiful species are on the verge of
extinction and it is feared that without
action, most of the island’s remaining
original vegetation will disappear
within the next 20 years.
The island is home to over 1,000 known
orchid species in 59 genera. Over 90% of
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ANGRAECUM LONGICALCAR (BOSSER) SENGHAS
these are endemic to the island and most
are known from very few specimens or
appear to have restricted distributions
with small populations. Preliminary
conservation assessments for a sample
of species suggest that as many as 70% of
species are threatened with extinction,
but there are insufficient data to make
accurate assessments. Hundreds of
species are found only in one or two
locations in the wild and are threatened
ORCHIDS SOUTH AFRICA
Angraecum longicalcar showing the long spurs.
ORCHIDS SOUTH AFRICA
ANGRAECUM LONGICALCAR (BOSSER) SENGHAS
128
by habitat clearance through logging,
charcoal production and agriculture, in
addition to the collection of the rarest
and most charismatic orchids for the
horticulture trade.
Madagascar is the only country outside
the United Kingdom where Kew Gardens
maintains a permanent presence. A local
team from Madagascar, working with
Kew UK staff and local institutions, make
a significant contribution to research and
conservation in the country. One of the
six target species selected for protection
by Kew is Angraecum longicalcar formally
known as Angraecum eburneum var.
longicalcar. The enormous length
of the nectary has been considered
sufficient to reproductively isolate
Angraecum longicalcar from Angraecum
eburneum and, therefore, recognize it
as a separate species. The difference
in habitat reinforces this contention
as it is geographically isolated from
Angraecum eburneum by more than 100
km in distance. Apart from this the
flowering period is also different. The
name longicalcar (pronounced longghee-KAL-car) is a compound Latin
word meaning “long spur”. The spur
on Angraecum longicalcar can reach up
Angraecum longicalcar: close up of the
flowers.
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ANGRAECUM LONGICALCAR (BOSSER) SENGHAS
to 40 cm in length compared to that
of Angraecum eburneum which is from
6 – 8 cm. As part of the Kew project,
seedlings of Angraecum longicalcar
are grown in greenhouses at the Kew
Madagascar Conservation Centre, some
of which have now been re-introduced
to the wild on the Itremo plateau east of
Ambatofinandrahana with the help of a
local community and school children.
This centre has an extensive programme
surveying orchids and collecting seeds
for seed-banking or cryopreservation.
Natural habitat
Angraecum longicalcar grows in the central
highlands of Madagascar at altitudes
of 1,000 to 1,200 metres. It occurs in
the provinces of Antananarivo and
Fianarantsoa where it grows in protected
areas. In the environs of Analavory
around Lake Itasy, this species grows
semi-terrestrially or lithophytically on
rocky marble outcrops or inselbergs, on
west facing slopes, often in almost full
sun. These plants grow in association
with succulent euphorbias and lilies.
In another location, a plant was found
growing epiphytically 6 metres above
ground in the crotch of tree branches
Angraecum longicalcar showing its
extensive root system.
ORCHIDS SOUTH AFRICA
The stem of this fairly large, elegant
plant is very thick and moderately short.
The stem including the basal leaves is
15 – 17 cm in diameter and as much as
60 – 80 cm long in old plants, which
commonly develop basal keikis. The
heavy roots (up to 5 mm in diameter)
are mainly confined to the lower portion
of the stem. The leaves are glossy, long,
quite fleshy, somewhat flatly V-shaped,
slightly unevenly bilobed at the tip and
measure 60 cm plus long and 9 cm wide
in adult plants.
high light in order to bloom successfully,
therefore, without good light blooming
will be inferior if it occurs at all. During
the course of field work it was discovered
that this species is rarely pollinated,
meaning that fruit production is low.
Possibly this is because the use of
insecticides during locust control has
reduced insect populations resulting in
poor pollination.
A specific moth species with a tongue
of up to 40 cm long keeps these flowers
pollinated and the species perpetuated.
Undoubtedly both moth and orchid
are totally dependent upon each other
for survival. Without the moth, the
orchid would never be pollinated
and very probably (although not yet
documented) this species of moth may
be totally dependent in its reproductive
phase upon the nectar that it gets from
Angraecum longicalcar.
From the hybridizer’s standpoint,
this species offers great possibilities.
Its vigour, strong inflorescence and
spectacular flowers fairly beg to be
hybridized with many small-plant
Angraecum species which are available.
The flower
Cultivation
in the gallery forest. The bioclimate of
the area is described as ‘sub-humid’.
Documented populations of Angraecum
longicalcar have been reduced to 2 –
5 localities partly due to the marble
mining in the area in which it grows.
Fires that ravage the area every year have
also reduced the population of plants to
near extinction. Important sites outside
the protected areas include Itremo and
Ambatofinandrahana. Latest updates on
the Kew Gardens website indicate that it
may already be extinct in the wild.
The plant
The inflorescence arises from the leaf
axil and arches horizontally from the
plant and is up to 85 cm long. The
buds start to show towards the end of
January/ beginning of February and
by the beginning of April the first
blooms are starting to open. It is quite
an event watching the long nectaries
unfold; they seem to grow centimeters
every day. When the spurs are rapidly
growing they are very sensitive to
bruising and sunburn which creates
ugly brown spots. Blooms can remain
up until June, so they are quite long
lasting. The inflorescence is green with
4 small enclosing bracts and the flowers
are alternate; the backswept sepals are
green-white and waxy, the labellum is
clear white, the column and anther cap
are pale green and the callus is white.
The green-white spur measures between
27 and 40 cm in length. The flowers are
strongly scented, mostly at night and
there are around 11 blooms per flower
stem.
Pollination
The plant only flowers when it obtains
enough energy to do so. It also requires
ORCHIDS SOUTH AFRICA
I grow my Angraecum longicalcar
plants in a greenhouse with opal
polycarbonate roofing with 50%
Aluminet shading underneath the roof.
I grow the original plant, which was
obtained from Madagascar and is now
nearly 20 years old, on the east side
with plenty of morning light and the
second plant on the western side with
only strong afternoon light. Both have
a nearby oscillating fan plus a window
which is left open for most of the
summer months. The constant airflow
I find a must for successful Angraecum
longicalcar cultivation. I try to simulate
the trade winds that blow in the area
of their natural habitat in Madagascar.
Summer temperatures range from
15°C to 33°C and winters from 10°C to
20°C if we are lucky! It can get pretty
cold here in George. I do use heating
to keep to the 10°C and would like to
get it even higher if it weren’t for the
cost of my 3-phase heaters! Humidity is
naturally quite high in George during
summer, but I constantly wet the
cement walkways to increase this when
necessary. Intermediate temperatures
are ideal.
ANGRAECUM LONGICALCAR (BOSSER) SENGHAS
128
Potting medium
Plants of this species can be potted in
a semi-terrestrial mix in view of the
conditions under which they grow in
their natural environment. I use a coarse
cymbidium-type mix with two grades of
bark plus stone, perlite and charcoal to
which is added a generous helping of
dolomitic lime and some bone-meal.
Large pots of up to 40 cm have extra
drainage holes to aerate the fleshy roots.
Due to the difficulty in repotting these
large plants they sometimes get left for
3 – 4 years before repotting. I repot in
early spring to give the plants sufficient
time to recover before the spikes come
out in January.
Feeding and watering
Due to the large size of the pots these
plants are only watered weekly in midsummer and only when it is warm. At all
other times and when it is cooler, they
get watered every second week. Feeding
is done every second watering. In the
summer months I alternate between
Seagro® organic fertilizer at 2 ml per litre
and a balanced hydroponic fertilizer at
2 gm per litre. In the cooler months I
use only the hydroponic fertilizer and
in the cold months of July, August and
early September I do not fertilize at all.
Pests and diseases
My Angraecum longicalcar plants are
prone to the occasional outbreaks of
scale and I keep a close watch to make
sure it doesn’t get out of hand. The
large fleshy leaves overlap considerably
and scale are normally found first
on the underside of the leaves where
they touch each other. If found early,
methylated spirits on a cotton swab
will clear it up, but I generally follow up
with a contact spray every two weeks for
a 6 week period. A systemic insecticide
can also be used if the infestation proves
difficult to get rid of. I have little or no
mealy bug in the greenhouse and do not
get plagued with slugs and snails.
I seldom have any fungal problems now,
but in 2006, a year after moving to George
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ANGRAECUM LONGICALCAR (BOSSER) SENGHAS
from Stellenbosch, I discovered that the
top fan of leaves had rotted at the base
presumably due to my heavy misting in
the summer months – something I am
now very careful not to do! I carefully
cut off the whole fan of leaves and
removed all the diseased lower part of
the stem which was brown and smelt
awful. I doctored the cut on the main
plant with cinnamon and sprayed the
whole plant with a fungicide. The fan of
leaves which I had removed was left to
dry in a cool place. After about 2 weeks I
repotted this section which luckily had
a few aerial roots hanging from between
the leaves. I left the plant fairly dry for
some time even though the leaves were
very dehydrated. Within 6 months this
new division had fully recovered and
was well rooted in its pot. It bloomed
the second year after being potted and
is the plant photographed with 3 stems
of flowers. The remaining larger plant is
the one rooted into the ground in the
main photo.
Specimen
Angraecum longicalcar makes a wonderful
specimen plant and is a treasured part
of my orchid collection. Having been
around for 20 years, it is definitely ‘an
old friend’. I would love to have it award
judged, but as you can see, it is not an
easy plant to move around.
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Bibliography:
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Andriantiana, J.L. 2003. Plants at Risk.
Angraecum longicalcar. Ravintsara 1(5):16.
Missouri Botanical Gardens.
Hermans, J. and Cribb, P. 2005. Orchids of
Madagascar. Orchids. Vol. 74 (11):836-847.
Hillerman, F.E. and Holst, A.W. 1986. An
Introduction to the Cultivated Angraecoid
Orchids of Madagascar. Timber Press. Portland.
Seaton, P. 2007. Angraecum longicalcar.
Between a Rock and a Hard Place in
Madagascar. Orchids. Vol. 76 (5): 368-373.
Stewart, J., Hermans, J. and Campbell, B.
2006. Angraecoid Orchids. Species from the
African Region. Timber Press. Portland.
Personal communication:
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Hermans, J. 2013
ORCHIDS SOUTH AFRICA