Most orchids are from the Tropics and Sub-tropics, where humidity is the norm. A lot of people in the US dislike humid places—they think it means heat, sweat and frizzy hair. But moisture in the air doesn’t necessarily mean high temperatures. In fact, I think about the Costa Rican mountains, where the air is cool and fresh. It is the only place I roll down my car window to enjoy the refreshing damp wind.
Through their pores (stomata), orchids perspire water and inhale carbon dioxide. These are their normal activities just like humans breathe in oxygen and breathe out carbon dioxide. The lower the water content in the air, the more water orchids lose. If they are losing water more quickly than their roots absorb, the plant will become dehydrated. The pseudobulbs will shrivel, the stems will become weak and the flowers will wilt prematurely.
While some plants are more tolerant of dry air, some are pretty moisture demanding. Generally speaking, the humidity should be at least 40% during the day and 60% at night. And because the heat in the summer will accelerate the water loss, the humidity in the summer should be at least 70%. Even though the weather report will tell you the humidity level in your area, it fluctuates quite a bit in your house, so do invest in a simple hygrometer to monitor the moisture level in your growing area.
If you don’t have an enclosed growing area, it’s fairly difficult to increase the humidity. But try these methods and they will at least help a little:
- Put your plants on a humidity tray. You can buy ready-made humidity trays. All you have to do is to fill the tray with water and place the plant on the grate over the tray. I personally don’t think those trays look very appealing, but you can make a good-looking one yourself by filling a pretty tray with pebbles. Then pour water in it but don’t let it totally cover the pebbles. Make sure that your orchids’ pots are not touching the water.
- If there is an occasional dry spell, you can mist your plant several times a day. This is a simple temporary solution, but does require manual effort. However, don’t mist it too late in the day, otherwise the leaves of the plants will stay wet throughout the night, which could promote diseases.
- If you have an outdoor growing area or greenhouse, you can hose down the ground or the under-bench areas. It would be better if the method is accompanied by a blowing fan to circulate the moisture.
- If you have a relatively confined growing area, you can use a humidifier. You can even buy a simple timer to switch the humidifier on and off. A powerful humidifier could be quite expensive, but if your growing area is not too big, a regular humidifier from the drug store will suffice.
- Install overhead mister if you grow outdoors on the balcony or patio. Many fashionable outdoor cafes in in dry locales install super-fine fog misters. Not only do they increase the humidity, but they also help to cool down the place. And because the mist is so fine, your plants will not be dripping with water. Make sure to turn it off (manually or with a timer) after the mid-day sun has passed.
If you live in a humid area, make sure that you provide enough air circulation to your plants, otherwise you would be inviting fungus and bacteria to party on your plants. Be sure to read my air movement page.