1)Light
2)Water
3)Temperature
4)Air movement
5)Humidity
6)Potting media
LIGHT
This is probably the single most crucial factor in determining whether or not your plants will bloom. The appropriate amount of light is necessary for proper plant growth and nutrient storage. Without the right light levels, your plant either cannot produce enough food stores to power a blooming cycle (if it gets too little light) or it may get sunburned and scorched or dessicated due to rapid transpiration (it if gets too much light).Generally, you can tell how much light an orchid needs by observing the foliage. For most plants, you want the leaves to be a light green color. When exposed to sufficient light, many plants darken their foliage with plum-colored pigments. Essentially, this is the plant's "suntan." It may take the form of spotting or the whole leaf may darken. This shows that the plant has as much light as it can stand and is trying to protect itself from burning. This is the ideal situation for good blooming. See the individual culture sheets for more detail on the light needs of specific genera.
Too much light: If the leaves become very yellow, move the plant to a shadier location. The same goes if you see sudden brown splotches or orange patches, particularly at the apexes of leaves or at folds where long leaves reflex. Light that is too intense can cause sun scalding. This is indicated by the large, bleached spots that eventually turn black, crispy, and dry, looking charred.
Not enough light: If the leaves become dark emerald green, move the plant to more light. This coloration shows that the plant wants more light to grow well. The plant will live indefinitely with light that is lower than ideal, but you probably won't see any flowers. The good news is that a large and otherwise healthy plant that has been grown for a long time without adequate light will often put on a dazzlingly impressive display once given desirable light conditions.
WATERING Watering is another important thing to get right. Most orchids are epiphytic. They grow on trees or other plants, and obtain their moisture from the air. Nutrients are obtained from rain carrying decaying matter over the roots. This means that they never stand in water in nature (Disas and Phragmipediums being noteworthy exceptions... but if you're getting into growing those, you need a lot more detailed information than this page is designed to provide). Accordingly, your orchids should not be allowed to stand in water in your home.
Orchids must be watered somewhat differently from most other plants, the most noticable difference being orchids' intolerance of dissolved salts.
How much water you need to provide, and how often, depends on several things:
How dry your conditions are.
The size of the pot.
The material the plant is potted in.
The type of plant.
How hot the weather is.
How actively the plant is growing.
How much wind the plant is expose to.
There really is no hard rule for watering that can be applied across all orchids, particularly bearing in mind that some homes are drier than others, small pots dry out faster than large ones, and some plants prefer more water than others.
In general, watch the plants -- they let you know when they need water. Crinkled leaves and shruken pseudobulbs are signs that more water is needed. The roots will tell you if you have good watering habits, too. Healthy roots are white, firm, and fleshy, with green tips, in plants that are not being overwatered (this is for genera that have velamen... Paphs, Phrags, and terrestrials are not included in this description). Overwatered plants have few good roots, and many soggy, mushy, brown, dead and otherwise rotting roots.
One watering rule you can live by is that most orchids tolerate being too dry much better than they tolerate being too wet.
When you water, let the water run freely through the pot. This helps to wash away mineral deposits and avoid salt buildup.
TEMPERATURE
Most in-home temperatures are acceptable for growing the most common types of orchids. Cattleya, Phalaenopsis, Paphiopedilum, Oncidium, Miltonia, etc. can all be grown with great success under normal home temperatures. In general, if it feels comfortable to you, these plants will feel fine, too. Diurnal temperatures between 65ºF and 80ºF are usually best, with noctural temperatures between 55ºF and 75ºF. Some plants, such as Phalaenopsis, actually require a period of marked difference between daytime and nighttime temperatures in order to initiate blooming; so if your home is utterly climate controlled and the temperature never fluctuates from day to night, you can actually have trouble blooming some kinds of orchids.
Most orchids are tough enough to grow outside their "ideal" temperature range. If for some reason you need to "stretch" an orchid's tolerance zone, one way to do so is by reducing the watering. This is particularly true for warmer-growing orchids forced to spend a little time under cooler conditions... they'll usually weather the cool period OK, as long as they aren't wet and cold. For cooler-growing orchids forced to endure hot weather, the key is lots of additional water and lots of good air movement. A cool grower exposed to hot temperature will bake in stagnant air, but would be fine under the same conditions if there is a fan blowing across the foliage (don't forget that increased air movement means increased transpiration... so adjust the watering schedule accordingly)
AIR MOVEMENT
Speaking of air movement... it is crucially important to most orchids. In their native environments, nearly all orchids are exposed to constant breezes. Moving air is very beneficial to the overall health of orchids. It helps cut down on disease problems, and also helps prevent cold or hot spots that can form on the leaves under adverse temperature conditions. A small fan mounted in the growing area will give you noticably better growing conditions and your plants will thank you by responding with more vigorous growth.
HUMIDITY
Most plants do best with humidity in the range of 60% to 80%, but the average home registers only about 30% to 40%. A heated home with lots of carpets and draperies may have as little as 5% ambient humidity.... far too low for orchids to thrive (or people, for that matter -- which is why humidifiers are so commonly employed for people with respiratory ailments).
If you have adequate humidity to raise other houseplants, you have enough to raise orchids. But if humidity is a problem for your other plants, then it will definitely be a concern for your orchids. No expensive equipment is necessary to provide more humidity for your orchids. Commercially available purpose-built humidity trays are very nice, but really any tray large enough to hold your plants -- and deep enough to hold some water -- will suffice.
To create a humidity tray, fill the tray with gravel or place a rack across the tray. Next, put water in the tray. The evaporating water will help the plants thrive in a dry environment. Be sure the plants are not actually sitting in the water. Never place orchids in standing water (having said that, there are many people who use a system called "semi-hydro"... but that is beyond this page's scope).
Gomesa crispa. Photo by Joseph Dougherty.
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POTTING MEDIA Most orchids are epiphytes. ORCHIDS WILL NOT GROW IN REGULAR POTTING SOIL!
I offer this warning because years ago, when I was first learning about orchids, I nearly killed a beautiful and large plant given to my wife (then girlfriend) as a gift by a friend. Fortunately, she still married me, even though I repotted her giant Oncidium into a dense pot of garden soil... and consequently reduced it from a couple dozen large and healthy psuedobulbs to two spindly little new growths that barely managed to survive solely because they weren't in contact with the dirt. I was trying to be helpful, but in my ignorance doomed the plant to a miserable setback (it has since recovered, after pouting for several years, but still has not yet returned to its former glory).
Epiphytes (which literally means "upon the leaf") are sometimes commonly known as "air plants." They grow on the branches of trees in the rainforest. The only real purpose of putting any kind of media in their pot is to hold the plant upright, and possibly also to aid a bit in moisture retention between waterings. The main function of the medium, though, is to provide support. Anything that does this and allows good air circulation around the roots is acceptable as a potting media.
Each type of media has its own advantages and disadvantages, and some of these are exacerbated by local growing conditions. The best way to choose a suitable media for your growing area is to speak with local growers and breeders to see what they are using. Common media include the following:
New Zealand sphagnum moss: most often used for orchids that need to stay moist, such as pleurothallids.
peat moss: Used for the same reason as sphagnum.
fir bark chips
redwood bark chips
osmunda fiber
tree fern fiber
coconut fiber
coconut chips
sifted perlite
granular charcoal
expanded clay pellets
cork (usually used as a slab to mount orchids)
rockwool
The size of individual particles in the media affects its water retention character. Small chips of a medium retain more moister than will large chunks of the same medium. All the media listed above dry at different rates. The media at the top of the list retain the most moisture, while those toward the bottom of the list dry out much quicker. If you tend to overwater, think about using the faster drying media. If you prefer to water less, use the media that hold moisture. Many people combine media (at OrchidMania, we typically use a mixture of fir bark, perlite, and charcoal) to suit their watering habits and preferences.
