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CATTLEYA CULTURE IN MELBOURNE by Barbara Walker
(Editors note since 2004 when this was written there has been a large revision of the genus Laeliinae and many orchids have changed name.)

The term Cattleya is used to cover plants of the orchid genus Cattleya as well as hybrids of Cattleya with related genera such as Laelia, Brassavola and Sophronitis. These are the parents that have been used for many years to produce plants of the Cattleya Alliance, often loosely referred to as cattleyas.

The abbreviations for these genera are: C. = Cattleya, B. = Brassavola, L. = Laelia and S. = Sophronitis. A hybrid between a Brassavola and a Cattleya is a Brassocattleya, abbreviated Be. Other abbreviations are: Blc. = Brassolaeliocattleya {Brassavola x Laelia x Cattleya), Lc. = Laeliocattleya (Laelia x Cattleya), Sc. = Sophrocattleya (Sophronitis x Cattleya), Sic. = Sophrolaeliocattleya (Sophronitis x Laelia x Cattleya), Pot. = Potinara (Cattleya x Brassa­vola x Sophronitis x Laelia), and Rolf. = Rolfeara (Cattleya x Sophronitis x Brassavola).

There are also a number of other closely related genera that will inter-breed with cattleyas, among them Epidendrum, Broughtonia, Diacrium, Barkeria and Schomburgkia. Two of the more commonly seen hybrids are Epc. = Epicattleya (Epidendrum x Cattleya) and Ctna. = Cattleytonia (Cattleya x Broughtonia).

Mature plants of the Cattleya Alliance require a minimum night temperature of between 8°C and 10°C but an occasional night temperature as low as 1°C can be tolerated if the plants are dry, have moving air around them and exposure to the low temperature is not prolonged. For younger plants, it is recommended that the stated minimum temperatures be maintained at all times if possible.

Members of the Cattleya Alliance most able to survive cold weather are those containing Sophronitis and/or Laelia. These hybrids can be grown in sunrooms or on verandas or patios covered with fibreglass. No heating is required provided that the plants are kept dry during cold weather. Cattleya hybrids and inter-generic hybrids containing Brassavola digbyana will survive temperatures down to about 5°C or even lower for a short time provided that the plants are kept dry.

Cattleyas require quite high light intensity to flower well but too much light will result in very yellow, hard leaves and stunted growth; if this is the case a little more shading is needed. Always grow cattleyas in filtered light (for example, under shade cloth with a shade factor of 50%) and be sure to avoid direct sunlight, which will burn the leaves during summer. When growing cattleyas indoors, place them close to the window but screen them from direct sunlight with a light curtain.

The relative humidity should be kept between 50% and 80% during the day but no higher than 50% at night. During the colder months, watering or wetting down the floors should be done early in the day to allow the atmosphere to dry out somewhat before temperatures fall at night. A humid atmosphere, in combination with low temperatures, can cause sepal wilt and spotting of the flowers.

If the plants are to be grown indoors, place an inverted pot (for the cattleya to sit on) in a tray of pebbles. Keep the tray full of water to maintain a humid atmosphere around the plant. Keeping several plants together helps to create a humid environment. During very hot weather or if you keep your house very hot, it's advisable to mist your plants several times during the day.

The tips of cattleya roots seal over when the plant enters its rest cycle and at this time (usually during winter) very little water is required, provided that the atmosphere is reasonably humid. Shrivelling of the pseudo-bulbs indicates that the atmosphere is too dry or that the plant needs to be watered more frequently. Provided your plants are potted in a very open bark mix (which allows plenty of air around the roots), a good watering every two or three weeks in winter is sufficient. Occasional misting is all that will be required at other times to prevent the pseudo-bulbs from shrivelling. A more carefully monitored watering regime will be required if a finer potting mix is used. If in doubt, delay watering for another day and wet the floor instead. Never fertilise when the plant is resting, or you may damage its roots.

When the rest cycle comes to an end and the roots resume active growth (indicated by green root tips about one centimetre long), gradually increase the frequency of watering to two or three times each week. After watering, a liquid fertiliser (at never more than half the manufacturer's recommended strength) can be applied. The ideal fertiliser program is little and often; if you prefer to fertilise your plants frequently, then dilute the fertiliser to one eighth of the strength recommended on the packet. Any liquid fertiliser is suitable, although I recommend that you use organic and inorganic fertilisers in rotation.

Cattleyas grow in nature as epiphytes, often clinging to tree branches where they get an abundance of air movement to dry their roots quickly after rainfall. Their roots are enclosed in a cover of velamen that acts like blotting paper, absorbing both liquid water and moisture from the atmosphere and transferring it to the roots. The velamen of healthy roots is white when dry but changes to green when it is wet. Cattleyas love to have their roots unconfined and the healthiest roots are generally to be found on plants that have outgrown their pots so that they hang over the rim. If you grow your cattleyas in a glasshouse or other enclosed area where the humidity can be closely controlled, you may prefer to mount your cattleyas on cork or bark slabs, rather than growing them in pots. I have found that mounted cattleyas will grow equally well either hung vertically or horizontally and, as all the roots are exposed to the air, there is no fear of them rotting.

 

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