Protect your orchids like you protect yourself. Too much or too little, orchid heat can be dangerous..

"Look closely. Can you spot the beetle on that orchid leaf??" Perhaps the orchid heat is appropriate :)

Orchids require protection only from frost and snow.

It's not rocket science..

You can easily keep a temperature check on orchid heat by noting their responses.

*Cold slows down growth and may cause the leaves to become brittle. If the plant freezes or if frost is too severe, the leaf tissues may be ruptured, developing soft, watery brown-and-black spots.

*Consistently high temperatures cause weak, rapid, immature growth. Growth is thin and slender, the leaves become soft and flabby, and the rhizome can't hold the pseudobulb erect.

Most beginners in orchid culture will be perplexed by the problem of supplying orchid heat by artificial means. The subject still is debatable. Climatic conditions from California to New York vary so widely that a solution for one area leaves the problem unsolved for the next. The only consistently logical approach is to realize that orchids must be protected from extreme and continuous cold.

Grow your orchids as cold as is compatible with their health. Provide orchid heat only when necessary. The closer you can imitate natural conditions without using artificial heating devices, the more successful you will be, the less labor your plants will require, and the more sturdy will be their responses.However, remember that more damage is done by heat than by cold.
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This does not mean that warmth is not necessary to all orchids, nor does it preclude the use of artificial heat in rigorous climates. It implies that man-made heat cannot compete beneficially with nature's stimulating warmth. Orchid heat that is artificial is a temporizing and last resort.

Orchids are hardier, more resistant to cold, than is popularly recognized even today. The epidendrum frigidum is always found where snow is a constant companion. The orchids of Indo-China often are covered with hoar frost in winter. Many Mexican orchids are subjected to sub-freezing temperatures in the Sierra Madre del Sur mountains.

Want some history on orchid temperatures?

In the orchid country of the Andes, temperatures as low as 20° F. are not uncommon. Many of these orchids, in culture, have withstood consistently low temperatures, 32° F. and less, if the air and the potting compost are dry at night.

On the other hand, a few orchids—those from tropical lowlands—would quickly die if exposed to mild cold. They require higher temperatures. Fortunately, not many of these are worth the trouble of growing. Also, many orchids from below the equator are not adapted to our seasons; our winter is their summer. For them, some sort of artificial heat is usually desirable.

Orchids may be wintered in cold frames, Wardian cases, terraniums, and warm house windows. Such miniature greenhouse structures can be simply and easily equipped with thermostatically controlled heating units or infrared lamps, which automatically give orchid heat and light when needed. Small greenhouses can use gas or oil heaters, hot water or steam systems.

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Most orchids come from one of three climatic areas and, accordingly, are divided into three temperature groups:

(1) cool orchids from the higher mountains;

(2) intermediate orchids from the plateaus; and

(3) warm orchids from sea-level countries.

During the past century a temperature chart has been worked out for the three groups. The temperature levels maintained by orchidists today are nearly 40 per cent lower than those once thought to be necessary —and are still dropping. At present these are the accepted minimum optimum temperatures for each climatic group:

Cool orchids, 50° F.

Intermediate orchids, 55° F.

Warm orchids, 65° F.

Learn to grow orchids at not less than these temperature levels before you experiment with lower ones. The maximum temperatures are not given, since all orchids, except one genus, the cool odontoglossums, can withstand high temperatures if they are fed well and supplied with abundant humidity during the day.

All orchids are harmed by high night temperatures, which weaken them, making them easy prey to diseases and rots. A difference of 20° between day and night is not too much. Fluctuating temperatures help to harden growth, stimulate the internal chemical changes which initiate new growth and flowers.

But sudden extremes of orchid heat and orchid cold are not advisable for orchids under artificial culture. They will work better for you if they aren't overworked. Make temperature changes gradually. When in bloom orchids may be placed in a slightly cooler and drier atmosphere and more even temperature; the flowers will last longer.