The cool orchids comprise several lovely kinds, some of which are suited to growing in an orchid case in a room where the winter night temperature drops to 50° degrees Fahrenheit or can be kept between 50° and 55° degrees Fahrenheit (not over 55° degrees Fahrenheit).
You can choose between those that do well with moderate light, such as those required for phalaenopsis, and those that must have bright light.
Remember, however, that even less light-demanding kinds deserve the best light you can give them. There is not quite a wide choice in the cool group as in the intermediate and warm groups.
The kinds specifically suited to the 50° to 55° degrees Fahrenheit temperature range do not like winter temperatures above this level but, like most other kinds of orchids, will take warmer summer nights.
A fourth group is so intolerant of heat that we might call them “cold” orchids. They require air-conditioned greenhouses in many parts of this country.
These are chiefly the high-altitude odontoglossums, such as O. crispum and its hybrids, whose culture is tricky at best and which we will not take up for this reason.
The methods of handling the cool orchids in an orchid case are careful ventilation to prevent constant saturation of the air and the building up of heat, shading against the sun’s heat at its peak, and attention to proper night temperatures.
These Grow Cool
The plain-leaved cypripediums, such as Cypripedium Insigne and its hybrids, are good subjects for the cool case, and many growers do well with them in a cool window.
If the lists of dealers do not specify which of these are cool growing and which are warm, it is better to ask before buying.
Miltonia
Miltonia is not as widely grown as cypripediums, but several indoor growers have had success with them, and where cool conditions are possible, they are certainly worth trying.
They make good companions for cool tips since their light requirements differ. They are botanically related to odontoglossum and oncidium and come from the cool altitudes of the South American rainforests.
They are pretty plants with somewhat flattened pseudobulbs and slender leaves. Their nickname, “pansy orchid,” describes the character of their flat, gently rounded flowers.
The chief problem is to keep them cool enough in areas with hot summers. The cypripediums are more tolerant of summer heat than Miltonia.
If you live in a warm climate, we would not advise Miltonia for your first orchids, for they require an experienced hand where conditions are not ideal.
Light and Shading Requirements For Miltonia
They should be shaded sufficiently from the sun at its peak to not have great heat, yet they must have enough light to mature their growths well.
An east exposure is perhaps best, where they can receive good light in the morning before the day becomes hot. They should be given good light through the winter.
Potting and Repotting For Miltonia
Miltonia is grown in this country in the soft, brown osmunda fiber. Some growers pot them every year in pots large enough to accommodate the year’s growth. Other growers pot them every two years.
They should be potted when new growth starts in the spring, but do not tolerate being shifted in hot weather.
If new growth has not started by April, you have a choice of potting them in anticipation of new growth or waiting until early fall.
Since our fall weather is often quite warm, potting in the spring is preferable. About one-third of the pot should be filled with crock for drainage.
The fiber should be firm, and some growers like to have it convex on the surface to ensure aeration at the base of the plant.
Watering and Fertilizing Miltonia
Miltonia should be watered frequently enough to keep the fiber damp, with the usual care not to produce a soggy condition.
During their growing season, they benefit from applications of fertilizer, as suggested for both cypripediums and phalaenopsis.
Some Miltonia Species
Some of the well-known species have large, showy flowers, and many hybrids have been made from them. M. roezlii bears two to four large flowers.
The sepals and petals are white, the latter tinged with purple at the base, while the large white lip is yellow at the base. This species is a bit more tolerant of warmth than the others and might be worth a try where summers run warm.
M. spectabilis, which gives one large flower to a stem, is notable for its violet-purple lip set off by blush-colored petals and sepals.
M. vexillaria bears up to ten flowers to a stem of a lovely pink color. Several horticultural varieties of this species range from yellow to purple.
Dendrobium Nobile: A Deciduous Type
Again, here is a genus that has members to suit various conditions. D. nobile, which requires bright light, can be grown along with intermediate kinds in the summer but must be put in a cool spot at least during the fall and early winter to make flower buds.
We keep it with cool orchids all year round in a greenhouse where it receives bright light. It is grown successfully by some indoor growers who can give it both good light and cool nights when the flowering time comes.
D. nobile is what we call a deciduous type. Its pattern is to flower on the growths made the previous year, not on the current season’s growths, and these 18-month-old growths lose their leaves just before flower buds are made.
Watering and Care For Dendrobium Nobile
The 2- to 3-inch flowers come from the upper nodes of the jointed pseudobulbs, in nodding groups of two or three.
They are velvety, with rounded sepals and petals, while tinged with purple, and a round tip that is purple bordered with white.
The plants should have a generous watering while growing and two periods of lessened watering between the completion of growth and formation of flower buds and between the end of flowering and the start of new growth.
Evergreen Types: Dendrobium Thyrsiflorum and Dendrobium Densiflorum
Dendrobium thyrsiflorum and D. densiflorum are evergreen types that have four-angled pseudobulbs bearing four or five dark, glossy leaves.
The flower sprays arise from the swollen upper nodes and bear an 8- to a 10-inch long, densely rounded cluster of completely charming little flowers.
The former has white sepals and petals and a yellow lip, while the latter is all yellow, and both have rounded lips fringed.
They have a sparkling crystalline texture. They are grown with the same temperatures and light conditions as D. nobile but do not have as pronounced rest periods.
Some Need More Sun
The odontoglossums need more sun than the cool cyps and so are suggested as companions for the dendrobiums.
It could be, however, that a few odontoglossums and dendrobiums could occupy the front half of a case near the light source and would serve to break the light for some cyps and miltonias.
The odontoglossums listed here should be handled pretty much like the cyps, not being allowed to dry out in the pot, and should have a mist spray over the foliage during the bright hours.
Odonto bictoniense gives sprays of small yellow-green flowers with a rose-colored lip and blooms in the fall.
Odonto pulchellum is spring flowering, with small sprays of white flowers that smell like lily-of-the-valley.
Odonto Rossi gives short sprays of rather large flowers, white marked with dark brown, in winter.
Ideal Conditions For Growing Cymbidium Orchids
The conditions under which cymbidiums are most easily grown and under which the average grower will be successful are not necessarily the only conditions under which they may be grown.
The ideal condition is syringing of the foliage in warm, bright weather. The syringing helps to keep control of their chief enemy, the red spider.
They are known as “heavy feeders” and should have a weekly application of chemical fertilizer during their growing season.
Adapting Shading and Ventilation For Summer
Shading has to be adjusted to the season and local conditions. During the summer, although they demand good light, the hot summer days allow the heat to build up too much in the greenhouse.
The shading must be applied to the glass, but not so heavily as to deprive them of good light.
It must be combined with free ventilation and a fan to keep the air circulating. The ventilators can be left open day and night.
Some growers move the plants out of the greenhouse for the summer, either into a lath house or under tall trees.
Although cymbidiums can take an occasional frost without apparent damage, it is wise to move them back into the greenhouse before frost is expected.
Adjusting Shading and Light For Winter and Flowering
As cooler days come on, increase the amount of light gradually. As winter arrives and flowering begins, shading will have to be adjusted to the locality.
Less shading is necessary in cold climates, where the sun does not build up the heat in the greenhouse so much.
In warmer climates, as on the West Coast, the flowers must be protected from the warm sun. Areas with more or less dull winters will allow cymbidiums to have clear glass.
Growth Patterns and Flowering Times of Cymbidiums
New growth starts in late winter or early spring in some kinds or late summer in others.
Growths that start early should produce spikes that autumn, but those that start in the summer will not flower until the following year.
In the latter types, vegetative growths come shortly before spikes start from the same pseudobulbs.
Cymbidium hybrids are superior to the species and are more easily obtained.
44659 by Rebecca T. Northen