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Zygopetalum mackayi Hooker

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Charles and Margaret Baker

Zygopetalum mackayi Hooker

AKA: N/A. 

ORIGIN/HABITAT: Southern Brazil from the states of Minas Gerais and
Espirito Santo in the north to Rio Grande do Sul in the south. Plants grow
as terrestrials in sparse woods, on brushy gentle slopes, or on grassy
plains or meadows near forests at 4250-5600 ft. (1300-1700 m).

CLIMATE: Station #83781, Sao Paulo, Brazil, Lat. 23.6S, Long. 46.7W, at
2628 ft. (801 m). Temperatures are calculated for an elevation of 4500 ft.
(1370 m), resulting in probable extremes of 94F (34C) and 26F (-3C). 

F AVG MAX        60   61   61   62   66   69   71   73   70   67   62   60
F AVG MIN        47   47   49   51   53   56   57   58   56   53   48   48
DIURNAL RANGE    13   14   12   11   13   13   14   15   14   14   14   12
RAIN/INCHES     1.5  2.1  3.5  4.6  6.0  9.4  8.8  7.8  6.1  2.3  3.0  2.4
HUMIDITY/%       75   73   77   78   80   80   82   83   81   82   80   79
BLOOM SEASON     **   **   **    *              *    *    *   **  ***  ***
DAYS CLR @  9AM   5    7    3    4    4    5    3    1    2    2    1    2
RAIN/MM          38   53   89  117  152  239  224  198  155   58   76   61
C AVG MAX      15.6 16.1 16.1 16.7 18.9 20.7 21.7 22.8 21.1 19.4 16.7 15.6
C AVG MIN       8.3  8.2  9.3 10.5 11.6 13.2 13.8 14.3 13.2 11.6  8.8  8.8
DIURNAL RANGE   7.3  7.9  6.8  6.2  7.3  7.5  7.9  8.5  7.9  7.8  7.9  6.8

Cultural Recommendations:

LIGHT: 2000-3000 fc. Relatively bright light is required by most
Zygopetalums, and healthy plants that do not bloom usually have inadequate
light. At proper light levels, the leaves should be light green. A
yellowish cast to the leaves indicates too much light while soft, weak,
dark green leaves indicate too little. Many growers successfully grow
zygopetalums under the same conditions and as companions of cymbidiums. 

TEMPERATURES: Summer days average 69-73F (21-23C), and nights average
56-58F (13-14C), with a diurnal range of 13-15F (8-9C). Growers report
that these plants will tolerate much warmer temperatures for short periods
without adverse effects. 

HUMIDITY: Near 80% for most of the year, dropping to near 75% in winter
and early spring. 

WATER: Rainfall is moderate to heavy from spring to early autumn, but
conditions are somewhat drier in late autumn and winter. Cultivated plants
should be kept evenly moist while actively growing, but water should be
gradually reduced in autumn. Plants should not be allowed to dry out
completely, however. 

FERTILIZER: A balanced fertilizer, mixed at 1/4-1/2 recommended strength,
should be applied weekly during periods of active growth. Many growers use
a fertilizer with lower nitrogen and higher phosphate in autumn. This
improves blooming the next season and encourages new growths to harden
before winter. Pots should be leached every few weeks to prevent salt
buildup, especially when fertilizer is being applied most heavily. Plants
should first be watered normally to dissolve any accumulated salts. An
hour or so later, the medium is flushed with water equal to about twice
the volume of the pot. Year-round leaching is important in areas with
heavily mineralized water.

REST PERIOD: Winter days average 60-61F (16C), and nights average 47-49F
(8-9C), with a diurnal range of 12-14F (7-8C). Growers report that these
plants will tolerate temperatures near freezing for short periods, but it
is better if they are not exposed to such extremes. While rainfall is
lower in winter, some is received each month. Also, additional moisture is
available from heavy dews, which are common. Therefore, water should be
reduced for cultivated plants so that they become somewhat dry between
waterings, but they should not be allowed to dry out completely.
Fertilizer should be reduced or eliminated until water is increased in

GROWING MEDIA: Plants are usually grown in pots filled with a relatively
coarse, well drained medium. Most growers use either fir bark or a mixture
of bark and moisture retaining additives. Rose (1993) recommended a mix
made up of equal parts of fine and medium fir bark with about 10%
large-grade perlite added. Because plants have rather large and extensive
roots, relatively large deep pots are normally used. Repotting should be
done just as new root growth is starting, often when new growths are about
half completed, or as soon after flowering as possible.

MISCELLANEOUS NOTES: The bloom season shown in the climate table is based
on cultivation reports. Zygopetalum mackayi is often confused with the
much more common Zygopetalum intermedium, and plants in many collections
are mislabeled. The most easily apparent differences are that in
Zygopetalum mackayi the petals are considerably shorter than the sepals
instead of being about the same length, the inner part of the lip is only
slightly roughened instead of noticeably fuzzy, and the underside of the
column is smooth instead of fuzzy.

Plant and Flower Information:

PLANT SIZE AND TYPE: A moderate to large sympodial terrestrial plant 14-23
in. (36-58 cm) tall.

PSEUDOBULBS: 2-3 in. (5-8 cm) tall and 1-2 in. (3-5 cm) in diameter. They
are bright green and smooth when young but become yellow-green and very
wrinkled with longitudinal furrows when older. The young pseudobulbs are
protected by 2 or more leaf-like sheathing bracts which grow from the
base, but these bracts become dry and fibrous with age. 

LEAVES: 2-3 leathery, strap-like, bright-green leaves with prominent veins
grow from the top of the pseudobulb. They are 12-20 in. (30-50 cm) long,
about 2 in. (5 cm) wide, and have long tapering tips.

INFLORESCENCE: 1 strong, erect spike that may be up to 39 in. (100 cm)
long emerges from the sheathing bracts at the base of the new growth. 

FLOWERS: 5-10 blossoms near 3 in. (8 cm) across are evenly spaced along
the inflorescence and often open simultaneously. The waxy flowers are long
lasting and are very fragrant. The sepals and petals often curve inward
slightly but usually recurve at the tips. They are yellowish-green with
large irregular blotches of reddish-brown or maroon. The large, flat
opening lip is white with dark red to almost blue veins radiating from the
base. These veins may have small hairs, which are the same color as the
vein, along their length; but these hairs are almost absent on some



Associação orquidofila de São Paulo. 1977. Native orchids of Brasil.
Associação orquidofila de São Paulo. 

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

McQueen, J., and B. McQueen. 1993. Orchids of Brazil. Timber Press,
Portland, OR. 

Pridgeon, A. ed. 1992. The illistrated encyclopedia of orchids. Timber
Press, Portland, OR. 

Rentoul, J. 1985. Growing orchids. book 2. Cattleyas and other epiphytes.
Timber Press, Portland, OR.

Rose, J. 1993. Orchid care - Zygopetalum. American Orchid Society Bulletin

Veitch, J., and Sons. [1887-1894] 1963, 1981. Manual of orchidaceous
plants, vols. I-II. James Veitch and Sons, Royal Exotic Nursery, Chelsea,
London. Reprint, vol. I, A. Asher and Co., Amsterdam, The Netherlands;
reprint, vol. II, Bishen Singh Mahendra Pal Singh, Dehra Dun, India.


Copyright 1997, Charles O. Baker and Margaret L. Baker
Sheet version 13936072

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