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Mesoglossum londesboroughianum (Rchb. f.) Halbinger

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Mesoglossum londesboroughianum (Rchb. f.) Halbinger

AKA: Odontoglossum londesboroughianum Rchb. f. At the time that the other
"Mexican odontoglossums" were transferred to the genus Lemboglossum, this
species was moved into the single-species genus Mesoglossom . According to
Halbinger (1982), "After trying very hard to fit Odontoglossum
londesboroughianum into one of the established sections or genera,
entirely without success, we have decided to make a new genus for this one

ORIGIN/HABITAT: Mexico. This orchid is known only from the state of
Guerrero where it grows at 3300-3950 ft. (1000-1200 m). Plants are found
mostly in areas of mixed vegetation where they grow on rocks in full sun
on east-facing slopes. However, plants occasionally grow epiphytically on
the surface of the ground. Halbinger (1982) included excellent habitat
information in the hope of assisting growers in finding suitable growing
conditions. With the same thought in mind, Halbinger's extremely helpful
information is included here. According to Halbinger, "The plants grow at
1,000 to 1,200 m altitude, on masses of early Cretaceous crystalline
rocks, in full sun or only light shade, usually facing east. The thick,
simple, whitish roots cling to the rocks, the plants growing upward in
hollows or even over the smooth surface. In the growing season the plants
receive the heavy rains of summer; during the dry season they are exposed
to occasional mists and to the dew of early morning. They prefer
well-ventilated positions, and it was observed that those plants most
exposed to direct sunlight, facing east or south, flower notably more
heavily than do plants in semi-shade. It is the feature of these plants
that they shed their leaves at the end of October, and that when they
resume growth in spring, the pseudobulbs are entirely leafless." 

CLIMATE: Station #76762, Chilpancingo, Mexico, Lat. 17.6N, Long. 99.5W, at
4462 ft. (1360 m). Temperatures are calculated for an elevation of 3600
ft. (1100 m). Record extreme temperatures are not available for this

F AVG MAX        85   87   89   92   92   88   86   86   86   87   87   86
F AVG MIN        56   58   61   64   66   68   66   66   66   64   60   57
DIURNAL RANGE    29   29   28   28   26   20   20   20   20   23   27   29
RAIN/INCHES     0.1  0.1  0.1  0.3  0.9  3.2  5.2  3.5  4.4  1.1  0.1  0.0
BLOOM SEASON                                                        *    *
DAYS CLR        N/A
RAIN/MM           3    3    3    8   23   81  132   89  112   28    3    0
C AVG MAX      29.4 30.6 31.7 33.3 33.3 31.1 30.0 30.0 30.0 30.6 30.6 30.0
C AVG MIN      13.3 14.4 16.0 17.7 18.8 19.9 18.8 18.8 18.8 17.7 15.5 13.8
DIURNAL RANGE  16.1 16.2 15.7 15.6 14.5 11.2 11.2 11.2 11.2 12.9 15.1 16.2

Cultural Recommendations: 

LIGHT: 3500-5000 fc. Very bright conditions are required. Plants will
adapt full morning sun, but slight shading may be beneficial at midday.
Strong air movement should be provided at all times, a brisk breeze is
extremely important for plants in extremely bright light. 

TEMPERATURES: Summer days average 86-88F (30-31C), and nights average
66-68F (19-20C), with a diurnal range of 20F (11C). The warmest season is
spring when days average 89-92F (32-33C), nights average 61-66F (16-19C),
and the diurnal range is 26-28F (15-16C). 

HUMIDITY: Reports are not available for this location. Records from other
stations in the region, however, indicate that humidity probably averages
75% most of the year, with 60-65% humidity in winter and early spring. 

WATER: Rainfall is light to moderate during the four-five month rainy
season that lasts from late spring into autumn. Amounts decrease rapidly
in autumn, which is the beginning of the six month winter dry season.
Cultivated plants should be watered often while actively growing, but
their roots must be allowed to dry out between waterings. Water should be
reduced dramatically in autumn. 

FERTILIZER: 1/4-1/2 recommended strength, applied weekly when plants are
actively growing. Many growers prefer to use a balanced fertilizer
throughout the year. Other growers use a high-nitrogen fertilizer from
spring to midsummer, then switch to a high phosphate formula in late
summer and autumn. Fertilizer should be stopped when leaves drop in late
summer or autumn. 

REST PERIOD: Winter days average 85-87F (29-31C), and nights average
56-58F (13-14C), with a diurnal range of 29F (16C). Although rainfall is
very low for 6-7 months in winter and spring, some additional moisture is
available from early-morning dew and mist. Cultivated plants should be
misted occasionally, with a rare, light watering if the pseudobulbs start
to shrivel or show signs of stress. Fertilizer should be eliminated until
new growth starts and normal watering is resumed in spring. New growths
may be susceptible to rot, so water should kept away from the expanding
young tip, especially if humidity is high so that evaporation is slow. 

GROWING MEDIA: New growths are widely spaced along the long rhizome, so
these plants are probably more easily managed if mounted on cork or
tree-fern slabs. However, mounted plants need high humidity, and during
hot, dry weather, they may require several waterings a day. If humidity is
low plants maybe grown in well-drained pots or baskets using a very open,
fast-draining, well-aerated medium that allows the roots to dry rapidly
after watering. Some use medium-sized fir bark or shredded tree-fern fiber
and add chunky perlite to help keep the medium open and also retain some
moisture. Including charcoal in the mix also helps hold the medium open
and keeps it from becoming sour. Conditions around the roots should never
become stale or soggy, and plants should be repotted immediately if the
medium starts to break down. Repotting may be done just as new roots start
to grow. This enables the plant to become established in the shortest
possible time. 

MISCELLANEOUS NOTES: The bloom season shown in the climate table is based
on reports from the habitat. Reports from growers indicate that cultivated
plants bloom in autumn and early winter. 

Plant and Flower Information:

PLANT SIZE AND TYPE: A rather large, sympodial lithophyte or terrestrial
with growths to about 22 in. (56 cm) tall. 

PSEUDOBULB: 3 in. (7.5 cm) long by 1.8 in. (4.5 cm) wide. The uniformly
olive-green, egg-shaped pseudobulbs are laterally compressed and develop
furrows on the flattened sides as they become older. When young, each
growth is partially enclosed at the base by 2 pairs of leaf-bearing
sheaths. Growths are spaced as much as 3 in. (7.5 cm) apart on a long
rhizome that normally grows in a straight row and the rhizome seldom
divides to develop more than a single new growth each year. 

LEAVES: Up to 18 in. (45 cm) long by 1.8 in. (4.5 cm) wide. Each growth
carries 2-3 narrowly lanceolate, sharply pointed, rather soft-textured
leaves are carried at the apex of each pseudobulb. All leaves are narrowed
toward the base. They are folded lengthwise along the midvein for some
distance above their point of attachment. The blades on the basal sheaths
are graduated in size with the lower ones being the smallest and the
uppermost ones sometimes being as large as the apical leaves. The blades
on the basal sheaths are quickly deciduous, usually dropping by the time
the plant blooms in late autumn. All leaves are deciduous in winter or
after flowering, however, and the pseudobulbs are bare when new growth
starts in the spring. 

INFLORESCENCE: 28-39 in. (70-100 cm) long, occasionally growing to 72 in.
(180 cm). The mostly erect, sometimes branched flower spike emerges from
the base of the most recently matured pseudobulb along the axil of the
upper basal sheath. The spike is often simple but occasionally branches.
Flowers, which are carried on the upper third of the inflorescence, are
arranged so that they alternate along each side of the spike. 

FLOWERS: 15-30. The attractive, long-lasting blossoms are 1.2-2.0 in. (3-5
cm) across. Flowers are bright golden yellow with concentric rows of
reddish brown spots, streaks, or blotches on the sepals and petals and
sometimes on the base of the lip. The sepals are sharply pointed at the
apex, widest in the middle, and somewhat narrowed at the base. The dorsal
sepal, which arches forward over the column, is 0.5 in. (1.3 cm) long by
0.3 in. (0.8 cm) wide. The oblique lateral sepals are 0.6 in. (1.5 cm)
long by 0.3 in. (0.8 cm) wide and open fully. The large, rectangular to
egg-shaped petals have rounded tips, are 0.5 in. (1.3 cm) long by 0.5 in.
(1.2 cm) wide, have undulate or wavy margins, and curve forward somewhat
toward the tip. The large, 3-lobed lip is about 1.1 in. (2.8 cm) long by
1.2 in. (3 cm) wide across the spreading, kidney-shaped midlobe. The base
of the lip, which is not clawed, is attached directly to the base of the
column. The very small, erect, pointed lateral lobes at the base of the
lip are separated from the midlobe by a long, narrow isthmus. The widely
spread midlobe has slightly ruffled margins and a shallow, V-shaped notch
in the center at the apex. The callus at the base of the lip is yellow and
white with reddish brown markings. It is shaped like half a bowl opening
toward the base. The slender, arching or bow-shaped, wingless, yellow
column is about 0.6 in. (1.4 cm) long. 



Halbinger, F. 1982. Odontoglossum and related genera in Mexico and Central
America. Orquidea (Méx.) 8(2):155. 

Hamilton, R. 1988. When does it flower? 2nd ed. Robert M. Hamilton, 9211
Beckwith Road, Richmond, B.C., Canada V6X 1V7.

Hawkes, A. [1965] 1987. Encyclopaedia of cultivated orchids. Faber and
Faber, London. 


Halbinger, F. 1982. Odontoglossum and related genera in Mexico and Central
America. Orquidea (Méx.) 8(2):155. 

Copyright 1998, Charles O. Baker and Margaret L. Baker
Sheet version 37851031

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