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by
Dennis Moser
One of the fascinating aspects of orchid-growing is the human history associated
with each plant we raise. I became acutely aware of this as Jan and I began to try
and become better growers, researching the particular needs of the plants that we
have chosen to grow. Each of us has our own reasons why we choose to grow orchids:
for some, it is the issue of conservation; for others, the shapes, colors, or scents
may hold special attractions. We begin to collect plants that hold some special meaning,
however simple. As we learn more about how to make our "favorites" thrive,
we (hopefully) gain an understanding of the human dimensions that each plant holds.
A year ago this January, we had attended a Greater Lansing Orchid Society meeting
and I was immediately, and inexplicably, drawn to a plant brought in by Randy Robinson.
It had warty, gnarly, silvery-green roots that dominated the cork mount. It wasn't
very large, less than six inches tall, but its star-shaped, white flower was nearly
as big as the plant and had a wonderful fragrance. I HAD to have one. Randy regretted
to tell me that the grower from whom he had purchased his did not have any in stock
just then, but that he might have some small plants later. He also said the grower
was in California, which did not make me too happy, as Jan and I had not gotten so
brave as to try buying many plants "mail-order." (Our first orchid together
was an Oncidium "Gower Ramsey" from Rod Venger of Venger's Orchids
in Colorado springs ... and Jan had bought it over the phone, having found his Web
site. But we still weren't too sure about this!) But I dutifully wrote down the plants
name and the growers name, after Randy told me that he would be coming to speak at
the Ann Arbor Orchid Society later in the spring and I might be able to ask him to
bring a plant along for me. And so began my initiation to Angraecum didieri,
Fred Hillerman of the Angraecum House, and the rest of the amazing Angraecoids ...
In 1804, the Colonel Bory de St. Vincent, in his "Voyages", described and
named a plant collected from the island of Reunion. It was a "large, erect,
epiphytic, terrestrial, or lithophytic plant up to 1.3 m tall ... " having flowers
that were " ... Large, showy, white with green or yellow-green sepals..."
He called this plant Angraecum eburneum, the name coming from the Malay word
for epiphytes, angrek or angurek. As you can see from the description,
there was some confusion about where it grew when Bechtel listed it in 1980, but
I'll come back to the problems of reading sources later in the column. In the years
that followed many more plants were found and described into this new genus called
Angraecum, it being the earliest described genus of the Madagascan and African Sarcanthoid
orchids. With time, it was clear that there were differences that warranted further
distinction within the genus, if not outright removal to other genuses. The Angraecum
genus was eventually reduced in number. Ultimately the following organization developed:
Angraecums are members of the Vanda tribe , which is divided into three sub-tribes.
These are: Sarcanthinae (Vanda, Phalaenopsis, Renanthera, Aerides, and Ascocentrum),
Angraecinae (Angraecum, Aeranthes, Jumellea, Sobennikoffia, Plectrelminthus, Cryptopus,
Oenia, Neobathiea, Gusonea, and Oeoniella), and Aerangidinae (Aerangis, Cyrtorchis,
Rangaeris, Mystacidium, Diaphananthe, Podangis, Eurychone, and Microcoelia). There
some 200 species of Angraecums and Angraecoid is now used to refer to the alliance
of the Angraecinae and Aerangidinae sub-tribes.
Angraecums continued to play their part in natural history. Another example is Angraecum
sesquipedale ("foot-and-a-half"), famous for the prediction by Charles
Darwin that a hawk-moth would be found having a tongue a "foot-and-a-half"
long to pollinate the plant, its beautiful, nocturnally-fragrant white blooms having
a spur, or nectary, that often reaches 18 inches in length. His prediction was corroborated
and commemorated when, long after Darwin had made the prediction, just such a hawk-moth
was found and named Xanthopan morganii predicta.
Angraecums are tropical-to-temperate so far as their geographic distribution (about
25° north to 34° south of the Equator) in tropical and South Africa, Madagascar,
and the adjacent islands, but we must remember that these areas range in altitude
from sea-level to 10,000 feet, so temperatures can range from torrid to quite cool.
Thus, within the sub-tribe, we have cool, intermediate, and warmth-tolerant plants.
One needs to establish from where the plant originates geographically but also what
the actual climate is to determine how to best grow them. This can get tricky when
the plants in question are hybrids. A recent addition to the literature, "Orchids
of Kenya" by Joyce Stewart (with excellent insitu photographs by Bob Campbell)
provides some succinct species
guidelines:
"All the species of Angraecum are easy to grow in cultivation. However, it is important to know the original source of each species because individual requirements vary, in particular the day and night temperatures that are maintained are very important for healthy growth. Angraecum dives, A. eburneum, and A. teres grow near the coast [of Kenya] and require warm night temperatures, high humidity, and thrive with bright light. The montane species [again, of Kenya], Angraecum chamaenthus, A. conchiferum, A. decipiens, A. humile, and A. sacciferum, require much cooler conditions at night with warm temperatures and considerable shuddering the day. They can tolerate drier conditions for part of the year but needing high humidity during the growing period. The widespread Angraecum erectum grows in a wide variety of conditions without difficulty. All species grow well in pots or baskets with a bark-based compost mix. Some of the smaller ones also grow well mounted on slabs of bark or cork oak."
It is also advisable to consider the original growth habits of the plant as well.
Angraecoids are usually described as epiphytes and lithophytes, but this can be misleading.
Angraecinae are more tolerant of pot-growing, whereas the Aerangidinae are not. So
one must be prepared to do some research into the cultural habits of the ones plants.
Sources of information can even seem contradictory.
Inspired by the A. didieri I had seen at GLOS, I was determined to locate
a specimen. Armed only with Bechtel's "Manual of Cultivated Orchids" to
guide me in learning about these plants, I noticed A. magdalenae , which had
what appeared to be a somewhat similar flower. And then, at the GLOS show, Oak Hill
Gardens actually had A. magdalenae seedlings for sale. They told me that it
would be several years before they would bloom, but I was too excited to be concerned
about waiting for the plant to reach blooming size. I had to start somewhere and
I thought this was a good place and time. We took it home and promptly looked up
that species to glean more secrets and details about its culture. Let this serve
as a caveat to all beginning orchid growers, investigate thoroughly when you get
anew plant, especially if it is a genus that is new or unknown to you. Read those
reference books carefully and try to find photos of the plants "in situ"
if at all possible. And by all means, talk with others who have grown them. Don't
be put off by remarks like "Oh, those are REALLY hard to grow - I can't grow
them ..." you may just happen to have the right conditions, but a little caution
IS a good thing. Why? Well, Bechtel describes A. magdalenae as being lithophytic,
meaning that it grows on rocks ... and the other angraecoid listed were epiphytic.
The photos showed the epiphytes growing as if they might if they were mounted on
bark much the way the A. didieri I had seen. The photo of the A. magdalenae
didn't show it in situ, so it wasn't a lot of help. Jan and I try grow as many of
our plants mounted as possible, so I reasoned that if it were lithophytic, then I
should be able to mount it. So I took it out its pot and mounted it. It sulked. It
was clearly not responding to what I had hoped was a more natural treatment.
A few weeks later, Fred Hillerman came to the Ann Arbor Orchid Society to speak about
angraecoids in general, angraecums in particular. He brought plants to sell and I
spotted an A. didieri that had the smallest nub of a spike starting and grabbed
it. Fred explained that itshould bloom without too much difficulty and that yes,
it would be fine to mount it. I toldhim about my unhappy A. magdalenae and
he smiled and told me that he would explainin his slide lecture, but that I should
put it back in a pot.
Fred had slides of angraecoids in nature ... and it all suddenly made sense. Yes,
A.magdalenae is lithophytic, but it grows in a layer of leaf mold and detritus
several inches thick on top of the rock out-croppings where it is found, frequently
in open sun. So I went home that evening, A. didieri in hand, and promptly
repotted the A. magdalenae.
Fred, certainly one of the more prolific writers on this group, says that water quality
is the first and foremost growing factor. It is followed closely by humidity and
air-circulation, with light levels, feeding, even temperature falling much further
behind. Why are water and air-circulation so critical for them? Consider the common
growth habits: they are usually epiphytic, occasionally lithophytic, occurring in
trees where there is frequently little detritus and debris into which the roots can
situate themselves. As a result, the root structures of these plants display flamenco
development that is highly effective at holding moisture. As mentioned above, they
are also highly effective as anchoring devices. Those amazingly large, warty, silvery-green
roots of the little A. didieri serve just that purpose, snatching every available
bit of guano-laden trickle of rain, fog, and dew that comes their way. But if there
is too much water or insufficient air movement to allow the excess to evaporate,
then the situation is created that allows fungus or rots to occur, ultimately destroying
the plant. Most of these plants are growing in areas with quite high relative humidity,
averaging well above 70%. Good air circulation is, therefore, quite important. Using
fans to provide enough air movement to just "rustle" the plant leaves is
adequate. Some growers find it most effective to have several fans, some of them
on timers to run part of the day and the others running continuously. Like wise,
if the water is too high in minerals or salts, the build-up can also prove fatal.
The solution (no pun intended) is to "leach" the plants on a regular basis
to remove salt build-up. By this, I mean literally drenching the plant with water
(use distilled water if your regular source would be too high in salts, although
ANY leaching is helpful), and then allowing it to drain. This can be done on a weekly
basis and definitely should be done prior to feeding the plants.
| Now about that A. didieri ... it responded to being mounted by quickly putting
out new roots, covering the bark on which I had mounted it.The tiny bud swelled,
turned into a spike and furnished us with a lovely bloom as big as the plant. It
was so fragrant that our growing area was filled nightly. But the story doesn't end
there, though I was quite happy to have bought a plant and successfully brought it
to bloom. By last September, the A. didieri was clearly getting ready to bloom again, this time with two spikes forming on opposite sides. The week of the Northwestern Michigan Orchid Society Show at Traverse City (late October), the first spike opened and it looked like a real contest see if the second one would open. |
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