Caring For Orchids Part Three: Temperature
killed. Temperatures above freezing and below optimum temperatures, may cause less damage, but damage will still occur. If your orchid has been subjected to freezing temperatures, the plant, especially the leaves, will turn dark and mushy. An orchid placed near a window exposed to freezing temperatures may receive damage to only the leaves that may have been touching the window. Orchids grown in too low a temperature, but not freezing, will become very weak over time leaving the plant incapable of defending itself against attacks by fungi and bacteria.
If you are growing your orchid outdoors, keep an eye on the temperature when it starts to get cold. If the temperature is going to be below 50°F (10°C) degrees for more than two hours, bring your plants indoors or protect them by covering them with newspaper, burlap, a light blanket, plastic bags, bubble wrap, etc. Even the cool growing orchids do not like temperatures much below 50°F (10°C) degrees. Temperatures below 50°F (10°C) degrees can kill a Phalaenopsis. Simply covering your orchids will NOT protect them if the temperature drops below 40°F (4°C) degrees!
Of course there are always exceptions to the rules. Cymbidiums, for examle, when accustomed to living outdoors, can stand colder temperatures. In fact, they need the colder temperatures to help initiate the flower spikes. I leave my Cymbidiums outside until it is just above freezing (It has even snowed on them). As long as the pseudobulbs don't freeze, the plant will be just fine. I also grow Bletilla striata here in Utah outdoors year round. In the winter it dies back but comes up every year in the spring. Our winter temperatures can reach below zero at times.
HIGH TEMPERATURE
Temperatures that are higher than your orchids' preferred range can also do as much damage as too low a temperature. High temperatures, in combination with intense light, is extremely dangerous to your plants. Some of the symptoms of too high temperatures are yellowing or blackening of the leaves or the tips of the leaves they could be burning. Leaves are dropping off, and the plant produces malformed growths and leaves. There are some orchids like Masdevallias that just fall apart when subjected to excessive heat. Orchids that are kept too warm at night become weakened, resulting in weak and leggy growth. As you may have expected, reducing temperature is much harder than raising temperature. Here are a few ways to achieve this.
1. If you are growing indoors and do not have air conditioning, move your plants outdoors under a covered/shaded patio. The night temperature will be much cooler outdoors than indoors.
2. Increasing air movement with fans will
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