Growing Cattleya Orchids in the Real World

This guide was written seeking to answer some of the questions most other orchid growing guides gloss over. Instead of providing a dry list of requirements, we hope to provide answers to real life problems such as "how hot is too hot for a leaf" and "how can I tell if a plant is getting enough water.  

Ever since English horticulturist William Cattley successful brought Cattleya orchids to bloom outside of their native habitat, they have been revered for their beauty and the subject of fascination to collectors. Because of their flower size, almost universal presence in collections, and historically high popularity. Culture varies only little among most of the Cattleyas making it possible to provide a general guide on how to grow the plants in this group. Cattleyas are the archetype of the orchids. For this reason, many published resources describe the care of other species orchids in terms of how requirements differ the Cattleyas. To whit, a collector who has mastered caring for Cattleyas will be successful raising many other orchids as well; “Care as for Cattleyas” is not an uncommon phrase. Fortunately, Cattleyas and most other orchids also have a wonderful way of telling you what they need. You need only pay attention and think about how each orchid is responding to your care.

Light Levels

In a nutshell, most Cattleyas grow best when exposed to unfiltered sunlight most of the morning and in the late afternoon with midday and early afternoon sun blocked or filtered to prevent overheating the leaves. Healthy leaves will get hot and develop burned spots or become yellow if exposed to midday sun. For this reason, midday sun must be blocked or filtered to reduce its intensity. If new leaves are narrower, more elongated than normal, and have a dark green color, it is very likely that that your light is insufficient. In general, you want to provide enough light such that new leaves are not excessively elongated and mature with a healthy looking, slightly light green color.
The light levels that are ideal for Cattleya are dependent on other factors as well. Some Cattleyas, such as C. luedemanniana and C. warscewiczii respond very favorably to light levels higher than most other Cattleyas, but measures must be taken to assure that the leaves of these species do not become too warm. Overheating of leaves is promoted by high ambient temperatures or still air, while lower ambient temperatures and strong air movement cool leaves and prevent overheating. As a rule of thumb, if you could tolerate a bath in water at the temperature you feel on a leaf, that leaf is at a safe temperature.

Light spectrum is as important as intensity. If you have your orchids in a tinted window it would be wise to find out what the tinting does to the light spectrum.  Colored tints would be more of a concern than neutral colors. 

When growing indoors it is possible for light reflecting from a neighboring home, building or other structure to change the spectrum of light arriving at your plant's leaves. If most of the light entering the window is not refelected, the effects will be minor. If, however, the light entering your window is largely indirect refelected light, it is possible for the color change to affect the way your plants grow.  One solution is to provide full spectrum artificial light to supplement the light entering the window. We will be adding a section on artificial lighting at a later time.

Temperature

Cattleyas grow and flower best at daytime temperatures of 70F to 85F and night temperatures in the range 55F to 60F. Seedlings and weak plants will grow faster and be less likely to develop fungus infections when night temperatures are 5 to 10 degrees higher than these ranges. Mature plants flower far more vigorously when given a 10 to 20 degrees diurnal (day to night) variation in temperatures. Many Cattleyas will do fine with day temperatures up to 95F if thier leaves are kept from overheating. This can be accomplished using strong air circulation with evaporation rates controlled usig a mid-day misting or by keeping humidity at the high end of the range.

Water

Cattleyas can tolerate very long periods of drought but will grow faster and larger with a watering schedule that keeps the forward bulbs from shriveling while still allowing the potting media to become completely dry before watering. After flowering, some plants do best with very little or no water during a rest period of a month or two. During this period the plant doesn’t put out new leaves or roots.

Humidity

Humidity controls how fast plants and potting media lose water. Some plants grow best with high humidity, while excessive humidity promotes fungal infections. Most Cattleyas do best with 50-80% humidity. Misting and humidity trays can be used to raise humidity, but take care not to get foliage wet late in the day because water may remain on foliage longer during cool night temperatures, resulting in fungal infections.

Pots, Mounts, and Baskets

Mounting is the most natural way to grow epiphytic and rupicolous orchids, but it requires higher humidity and more frequent watering, almost every day, to assure that the roots are provided sufficient moisture. Some advantages of this growing method are that overwatering is nearly impossible and mounted plants take little space when hung on walls and other greenhouse structures.
Growing orchids in baskets is a very good compromise between mounting and growing in pots. Like mounts, it is more natural for epiphytic orchids than pots and overwatering is far more difficult. Baskets provide better air access and drainage than pots, while allowing the frequency of watering to be much lower than is required for mounted plants. Baskets are our preferred method of growing plants, though we use mounts and pots also.
Pots are the most common, but least natural way of growing epiphytic and rupicolus orchids. On the other hand, pots are the best container for use when growing terrestrial orchids.
Plastic pots retain moisture longer than clay pots will require a little more water but promote root health by passing oxygen. Slotted plastic pots achieve the same result by allowing the roots access to fresh air. Clear plastic pots have several benefits, including allowing the roots to photosynthesize, the ability to see moisture, root rot, and the condition of the media.

Repotting

Repot your plants only when large scale root growth begins from new growths, typically in the spring. The importance of this point can't be overstressed.  Repotting at other times may cause a serious setback to your orchid. Plants need repotting when the potting medium begins to break down near the bottom of the pot or when the orchid grows over the side of the pot. Select a pot that will allow you to place the new growth at the center of the pot and allow about two years of growth. If the plant is being repotted due to deterioration of the media, it is best to remove almost all of the media during repotting. If you are repotting a plant only because it needs a larger container replace only the media at the bottom of the pot unless the media throughtout the pot is already deteriorating.   The potting medium should be course enough to assure water drains away quickly, but absorbent enough to make watering frequencies tolerable.  Bark is typical. More on this will be added to this guide at a later time.