OrchidSafari
Conservation series part 34
Isochilus
by Marilyn Light
Wednesday August 9, 2000
The Prechat handout follows the chat below:
MarilyninOttawa
Greetings everyone! For us in eastern North America, summer has been good
for orchids placed outside. The temperatures have not been too high or too
low, the humidity has been moderate to high but there has been good natural
air movement. Many epiphytic orchids thrive under these conditions. The
genus we will discuss during this session is one such orchid but it is not
often seen in collections. The reason? The flowers are small compared to
the bulk of the plant.
Before I begin discussing the genus Isochilus, I wonder if anyone grows this kind of orchid?
M._Jade
Marilyn I have Isochilus linearis. It blooms every year for me.
John_in_Arcadia,_CA
I tried once and had friends that grew it well.
Karen_Rolla,MO
Marilyn, this is another one I've never heard of.
barbara_in_no._CA
Yes, this genus is new to me.
MarilyninOttawa
This is a typical plant in cultivation. [picture]
Isochilus is a genus of thin-stemmed orchids close to but not a member of
the Laeliinae according to a recent molecular genetic paper published in
Lindleyana, June 2000. These orchids have creeping rhizomes from which arise
long thin reed-like stems. The roots are disproportionately large, 3 or
more times the diameter of the stems.
Kathy_in_N_Calif
"The roots are disproportionately large, 3 or more times the diameter
of the stems." Are they for storage? (I suspect so. ML)
MarilyninOttawa
I will be showing some flower pictures. Please disregard the bluish cast.
The flowers are pink or shades thereof. Flowers of the plant shown previously.
[picture]
Before we look at the variety of flower shapes possible in this genus, let
us consider where this orchid grows naturally. Isochilus is an epiphyte
or lithophyte. It grows naturally on trees and rock faces or boulders. Many
of the species named in the literature are synonymous or now considered
varieties of another species. Probably the most common species seen at shows
is Isochilus linearis, which has been reported from Mexico through Central
and South America including Bolivia, and Venezuela.
barbara_in_no._CA
Kind of tiny flowers? Short lived?
MarilyninOttawa
The flowers are reasonably long lived and some are quite showy as the spike
can consist of numerous blooms. This is a particularly showy Mexican species.
[picture]
MarilyninOttawa [96]
The best kinds have numerous flowers with a spreading perianth as in [picture]
M._Jade
What species was that picture?
MarilyninOttawa
I am not suggesting a species name for any of the pictures shown in this
session. All I can say is that they are different species.
MarilyninOttawa [102]
When you look at the flower, you can see some of the details which help
separate species such as the lip shape. This is the spike of the previous
single open bloom. [picture]
Marla
How large do these flowers get?
barbara_in_no._CA
That is very pretty, how big is the flower?
MarilyninOttawa
The widest flower could measure one-half inch in diameter but most are smaller
than one-quarter inch. Some such as the flowers of orange-flowered I. aurantiacus
are smaller still but still showy en masse.
M._Jade
According to RHS Manual of Orchids there are only 2 species of Isochilus.
Must be quite a bit of variation withing the species. [The exact number
of species is debatable but it is much more than two. There are I. aurantiacus,
I. linearis and I. major for a start. ML]
MarilyninOttawa
Isochilus flowers are generally produced on one side of the spike. [picture]
MarilyninOttawa
The individual flowers of this plant have a distinct broad lip with typical
purplish blotches. [picture]
MarilyninOttawa
This series of drawings will illustrate the variation between flowers which
can be used to distinguish one species from another. The drawings are courtesy
of Edward W. Greenwood. [picture]
MarilyninOttawa
You will see that individual flowers vary in openness, the angle of the
ovary in relation to the petals and sepals. The dissected flowers with petals
and sepals removed, leaving the lip, shows variation in lip proportion,
angle relative to the rest of the flower, and a curious folding at the base
of the lip.
Kathy_in_N_Calif
Those are what?? The column and the lip attachment?
MarilyninOttawa ]
The drawings on the left are the flowers in side view. The drawings on the
right represent the column (uppermost) and the lip (lowermost) after the
petals and sepals have been peeled away.
Marla
which numbers correspond to which species?
MarilyninOttawa
This is I 4496 [picture]
This is I 5500 [picture]
This is I 4704 [picture]
MarilyninOttawa
You might wonder why we need to distinguish species. Does anyone have any
suggestions?
CJ-Orchidflowerchild
CONSERVATION!!!!!!
MarilyninOttawa
Well, if you have two of the same species, you could cross pollinate and
be assured of same species progeny.
Kathy_in_N_Calif
And goes back to the notion that just cause something isn't large and showy
doesn't mean it doesn't need to be conserved. But surely identification,
description and naming is all a part of that too. Would Greenwood have to
submit all his work to the RHS in order to have the right to name these
species? I'm assuming he did the original work.
MarilyninOttawa
The naming will get done and much of that work is progressing now that more
sophisticated tools such as molecular techniques are available. What is
needed to name an orchid species is to describe the plant type and locality
including a brief botanical Latin description with a drawing and submit
this for publication in any one of a variety of journals, preferably refereed
journals. The type specimen is normally preserved in a herbarium for future
reference and study.
Karen_Rolla,MO
Marilyn, sounds like on site work for a botanical illustrator/taxonomist?
MarilyninOttawa
The color of these pictures is not the best as the slides are at least 10
years old. The flower color is rich pink with a lavender cast. The blue
tinge is an artifact that we were unable to adjust.
Marla
They are still nice... small flowers are hard to photograph.
MarilyninOttawa
One of the nicest Isochilus species for the hobbyist grower is I. aurantiacus.
The flowers are tiny, orange, and are carried at the tips of slender stems
of delicate greenish red foliage. The plant can be quite variable in height
in nature according the habitat. The higher you go up the mountain, the
shorter the plant becomes. Under intermediate culture, the plant grows to
12 inches. The orange flowers are small enough that a magnifying glass is
needed to appreciate the yellow lip and the reddish sepal tips. The effect
is appealing and judges are drawn to a well-flowered specimen.
M._Jade
Where does one find this orange delight. Isochilis aren't all that common.
Kathy_in_N_Calif
Andy's Orchids! www.andysorchids.com [found by doing a search on the Orchid
Mall -kb] [This catalog lists I. linearis and I. major but not I. aurantiacus.
ML]
MarilyninOttawa
You will find Isochilus species listed occasionally but not often because
demand is low. The best option is to ask vendors if they have any Isochilus
in their private collection and if so, if you can purchase a division. Make
sure that the division has roots.
M._Jade
Good advice. Especially about the roots.
Kathy_in_N_Calif
Marilyn, why are their roots 3x larger than the stems?
Marla
Question Marilyn..... Isos aren't supposed to be deciduous are they? I have
two little Isos and they are struggling... seemed to be dormant for months
and lost quite a few leaves.. now they are starting new growths but still
losing leaves on the old stems roots look ok
MarilyninOttawa
Isochilus are not deciduous orchids, at least not like Catasetums. Older
stems do eventually lose their leaves much like older leaves of Oncidium,
etc but this will be after several years. The tiny piece of Isochilus aurantiacus
I received from a friend had just two mature and one growing shoot. This
is still growing nine months later. Meanwhile four more shoots have developed
and these are now about two inches high. Young foliage is green but older
leaves are reddish. Some Isochilus are known to change foliage color (to
red) when flowering. This is somewhat like certain bromeliads.
Marla
So the color doesn't necessarily pertain to the amount of light it is getting?
[Foliage will color up with high light but more so when plants are about
to flower. ML]
MarilyninOttawa
Marla, your Isochilus will continue to struggle until roots are established.
These plants have very little substance up top. Over 80 percent of their
bulk is in the roots! The roots are very important and it is these that
we must promote when first establishing a plant. You might try: increasing
the light, raising the day temperature, raising the humidity. Keep the plant
in a small pot until roots become established. If the plant has roots and
is not growing then it is possible (and I say this without evidence) that
the plant is dormant. I personally would grow the plant in a transparent
pot so as to view the roots on a regular basis. I would watch what happens
as I raise the light, temperature, etc as previously suggested. Something
will trigger these plants to start growing but I cannot say exactly what
those conditions would be for every species or for your particular plants.
MarilyninOttawa
Marla, where are you growing your plants?
Marla
I have had them in a south east window with filtered light the leaves have
a definite reddish tint to them
Marla
So they do have a normal dormant period?
MarilyninOttawa
Plants can be found growing in humid lowlands to higher altitudes of several
thousand feet. I expect that most species can adapt to seasonal conditions
and would slow growth according to the situation. The succulent roots provide
a food and water store and likely a means to support seasonal dormancy.
By the way, different species bloom at different seasons. I. alatus of Guatemala
blooms in June while I. aurantiacus blooms in October.
M._Jade
Marilyn, would you say that many of the species of Isochilis have been rather
recently discovered?
MarilyninOttawa
Jade, good question. I expect that many plants have been collected over
the years but a lot have been given names based on the superficial appearance
of pressed specimens. Pressed tiny flowers can look very much alike. That
very striking orange-flowered species, I. auarantiacus was named only in
1981. A new species I. pitalensis of El Salvador, was named in 1981.
M._Jade
With flowers that small and the possibility of variations in species size
due to altitude it must be really difficult to separate a new species.
MarilyninOttawa
Yes Jade that is why Ed Greenwood has done the floral dissections and suggested
definitive features of the plants and flowers that can be used by investigating
taxonomists to separate species. For example, he observed that species can
be separated based on the patterns of stomata (breathing pores) on the leaf
surface. It is nice to have molecular methods available but good initial
separations can be achieved with less expensive methods.
MarilyninOttawa
Next session, we will be discussing genera beginning with the letter J.
I have chosen Jumellea (vandaceous) and Jacquiniella which is allied to
Encyclia. Both genera have fragrant-flowered species.
barbara_in_no._CA
Wonderful, I love Jumellea.
M._Jade
Sure would be nice if we could install a scent card in our computers for
theJumellea talk. :-)
MarilyninOttawa
Scent card. Hmmmm! Jacquiniella equitantifolia is fragrant at night. At
precisely 8 pm, the tiny flowers pump out lots of lily scent. Gets results
too as some of my blooms have been pollinated it seems.
MarilyninOttawa
Thank you all for your questions and support. Part of the fun doing these
more obscure genera is that I learn too! Good night all.
Marla
Thanks Marilyn! I know nothing about Jacquiniella.
MarilyninOttawa
Come and learn all about Jacquiniella in September Marla. Meanwhile, you
are likely to find some comments in The Encyclopedia of Orchids among other
references.
Karen_Rolla,MO
Night Marilyn! Thank you :-)
M._Jade
Thanks Marilyn. A really interesting program. I can't wait for the next
one.
--THE END
PRECHAT HANDOUT
Isochilus
Copyright Marilyn H.S. Light August 2000
As I write this introduction to Isochilus I am looking at a small division of Isochilus auranticus received from a friend last October. I admired the plant and its profusion of bright orange flowers so he simply pulled off a straggling piece consisting of three- 7 inch-long shoots and few roots and gave it to me. I potted it in damp sphagnum moss and kept it moist at intermediate temperatures over the ensuing months. At first a few small shoots appeared but apparently no roots: growth was slow. I say apparently because I have since observed a root had formed and run just under the surface. The color of the root is reddish green making it very much like the medium and difficult to spot. Seven months later and after two months of higher day temperatures occasionally above 80F, two new large solid roots have appeared and these are pink near the surface of the medium and white where they have penetrated deeper into the pot. The roots are 6 mm wide right until the tip and I suspect that they could serve as water and starch storage organs. I will take a closer look when there are more roots and one can be removed. Encouraging the formation of such roots and keeping them healthy is likely important to the successful culture of Isochilus. Although I must grow this specimen in a pot I will keep the potting mixture both moisture retentive and porous. I am considering using a mixture of chopped coconut and sphagnum with some torn styrofoam chips thrown in to keep the mix airy.
Isochilus (eye-so-ky-lus) is a small genus of tropical New World epiphytes found growing from Mexico through Central and South America. The small flowers are mostly shades of pink although occasional white-flowered clones have been seen.. Isochilus aurantiacus (Mexico) has orange blooms. The flowers are produced in small to somewhat elongated spikes from the tip of slender leafy stems. Plants can become quite large and heavy owing to the massive quantity of roots compared to leafy parts. Most species can be grown in pots but are perhaps most handsome when permitted to grow to specimen size mounted on a slab of wood or bark. Mexican species tolerate short periods of cold if sheltered from frost. Isochilus could make nice landscape specimens where they can be grown outdoors. The fine foliage is attractive even if a plant is not blooming.
The name Isochilus refers to the similarity of the floral segments. This may be true of some species but there are several whose lip is distinctly different from the other petals and sepals. Isochilus aurantiacus is unmistakable because of the flower color but the pink-flowered kinds can be confusing. The next time you see an orchid labelled Isochilus linearis, take a second and more detailed look. It could be another species.
As pointed out in previous sessions, knowing which species is which is a big first step in conservation.
Edward W. Greenwood has kindly provided some slides and flower dissections to show the degree of possible variation between specimens. These specimens are not named. Ed has developed guidelines of what one should look for when describing a flowering plant.
The following is Copyright E.W. Greenwood August 2000
Plants of Isochilus are the only orchids I know, other than Mormodes, in which all parts are asymmetric. The asymmetry starts with the leafy shoot, where the leaves are twisted about 90 degrees at the base, so that their similar upper or lower surfaces are seen on one side of the stem. The inflorescence is an asymmetric two-row spike, and the flowers are right- or left-handed. Each of the perianth segments and the column is asymmetric, although in some cases this is difficult to see.
Inflorescence - The front side and back of the inflorescence are often distinctly different in different species. The inflorescence is an asymmetric, two-ranked spike, with the angle between the ranks being species-specific.
Flower - The side view of a flower is definitive in many species. It shows the angle between the ovary and flower axes, an important specific character. Viewing a flower from the top will often reveal the lateral asymmetry of the flower. Viewing a flower from beneath will show the amount of fusion of the lateral sepals. Asymmetry is often visible in this view, especially in the angle between the flower and the ovary axes.
Petal and sepal (tepal) shapes are strongly uniform throughout the genus. Overdependence on these shapes as taxonomic characters has been the source of most of the confusion found in the literature of Isochilus. The base of the lip usually has one or two transverse, rounded, up-and-down folds just apically of the junction with the column foot, partially closing the space between the lip and the column, with the lateral sepals forming a nectary, sometimes with nectar. The axis of the fold crosses the lip obliquely, at a species-specific angle of up to ca. 20 degrees.
Interesting features which might become definitive characteristics for determining species are the patterns of epidermal cells and stomata (pores) on the underside of the leaf. The patterns are easily observed in fresh, pressed, and liquid-preserved material using cuticle peels. These investigations can be carried out even with non-blooming specimens. A trial using five morphologically distinct species-level specimens of Isochilus produced a key which distinguished each of them clearly using only the cell-pattern data.
The End
