Dr. Bill’s Orchids, LLC Basic Culture Sheet –
Cattleya (Catts)

Water:

In the simplest description, Cattleya should be watered once the media has become “dry”. The amount of light, air movement, type of pot that is is in, and heat your plant receives will also affect how soon your Catt needs watering. Summer months will need more frequent watering, Winter will need less. I normally suggest checking with your finger down to the first knuckle in the media to determine moisture levels with any new or newly repotted plant. If in doubt, wait two or three days. For many home growers, you may not need to water Cattleya for 7-10 days (or more in winter). Cattleya should not be left standing in water – this can lead to root rot. The goal is to keep the pseudobulbs plump and firm, if pseudobulbs start to shrivel, especially the newest ones, then you likely need to increase your watering.

Remember that new media (namely bark) will not retain water as well as “broken in” (not the same as “broken down”) media that has started to hold water more. Once new media is “broken in”, after a few waterings, you can usually tell by the weight of the pot whether it is time to water again.

General advice usually suggests that it is best to water in the morning for most in-home growers. Why the morning? Because it allows any water that gets into the nooks and crannies of the leaves to dry out in the heat of the day before the temperatures drop- cold + water = asking for rot, bacterial, or fungal issues. Some people have suggested using the corner of a paper towel to blot any excess water out of the crown after watering- doesn’t hurt, but not something I do. When watering, make sure to give it a deep drink as sometimes it takes a full 30-60 seconds before the velamen on the roots will start to turn green (sign of water absorption). Try to use tepid or lukewarm water when watering your plants.

Light:

Cattleya are “medium-high” light orchids (2000-4000 footcandles). They grow beautifully in an east window and can be grown in a south or west window if protected by a sheer curtain. Artificial lighting can easily be provided. Usually artificial lights are placed 6 to 12 inches above the leaves*, 12 to 16 hours a day, following natural day length. General rule of thumb is that a Cattleya’s leaves should be granny smith apple to olive green. If they are darker, it means the plant is not getting enough light; yellow-tinged leaves can mean the plant is getting too much light**. An easy way to measure light intensity without a meter is that there should be a blurry, but distinct shadow seen if you hold your hand one foot above the leaves.

Once the plant is in bloom you can place it anywhere in your home out of direct sunlight to enjoy. It can tolerate a little while of decreased light. If your plant does not re-bloom, slowly increase the amount of light that it receives. If light is increased too rapidly, they are prone to getting burnt.
*height above the leaf canopy depends on the light intensity you’re providing. Stronger lights should be farther away.
**with some species and then also some of the newer hybrids that are coming to the market, some leaves will have red anthrocyanins showing even if they are in almost near darkness, but they can also get the “red blush” that is almost equivalent to suntan. For mass produced hybrids, follow the green leaf rule, and yellowing that is almost the equivalent to sun-bleaching is bad.

Temperature:

Cattleyas are easy to grow because they enjoy much of the same temperatures we do – above 60º F at night and a range of 70º F to 80º F or higher during the day. 95º F is the maximum temperature recommendation. For most Cattleyas, growing a little cooler in the winter (maybe a 5 degree difference or so can be beneficial with blooming and best coloration of blooms)
A special note- there are some species that were previously recognized as the Sophronitis genus, but have now been lumped into the main Cattleya genus categorization. As a general rule, those Sophronitis species like to grow on the cooler side in comparison to your average cattleya. If you’re growing a Cattleya species plant, check with the grower or do a quick search online to see if it is one of the species that has some more particular growing needs, such as temperature.
Keep in mind that temperatures close to the window on a windowsill will be colder or hotter than your general house temperature (if growing on a windowsill, or anywhere really, I suggest having a thermometer/hygrometer). Fluctuating temperatures can cause bud drop on plants with buds ready to open. Also be wary of placing in the air flow of a heating or air conditioning vent! This can easily blast buds and/or spikes.

Fertilizer:

Any balanced orchid fertilizer (look at the numbers on the container, 20-20-20, etc.). Even better if you have a balanced orchid fertilizer with micronutrients added as well. If you don’t have that on hand, generic Miracle Gro can be used to fertilize your orchid at ¼ strength once weekly until you do get a more balanced formulation. Feeding weakly (1/4 -1/2 strength from box directions) weekly works well. I feed at approximately 120 ppm N one or two times a week during warm months and down to one or two times every 2 weeks during cooler months. At least once a month, use plain water to flush any accumulated salts from the potting mix.

Humidity:

Even though they have thick, waxy leaves, Cattleya will definitely appreciate humidity being between 40 and 70 percent. They will tolerate lower levels, but will do best in the range listed above. In very humid climates, as in greenhouses, it is imperative that the humid air is moving to keep nasty infections at bay. In the home, you have a few solutions to increase humidity: 1) set the plants on trays of gravel, partially filled with water, so that the pots are not sitting in water 2) group plants together to increase local relative humidity 3) plant in an unglazed clay pot and then nestle that pot into another unglazed clay pot (Credit to Neill Sams of Orchid Alley Kauai for this idea) 4) add a humidifier to your growing area (I personally like ultrasonic humidifiers for indoor growing)

Potting:

Best done in the spring, immediately after flowering, but they can technically be repotted at any time if absolutely needed. Usually, you want you avoid repotting in the Fall/Winter months if you can help it, as plants will take longer to get established in their new pots. Cattleya plants must be potted an aerated media- porous bark mix or sphagnum that isn’t overly compacted. Potting is usually done every one to three years. Mature plants can grow in the same container until the potting medium starts to decompose, usually in two years. Root rot occurs if plants are left in a soggy medium. Seedlings usually grow fast enough to need repotting yearly, and should be repotted in a medium-grade media. Mature plants are potted in a coarse to extra coarse- grade mix. To repot, remove all the old medium from the roots, trim soft, rotted roots, and spread the remaining roots over a handful of medium in the bottom of a new pot. Fill the rest of the pot with medium, working it among the roots, so that rhizome is at the top of the medium. When placing the plant in the new pot, put the old leads closer to one of the sides, to allow more room for the new lead pseudobulbs to have sufficient room to grow before they end up “crawling out of the pot”. If your newly repotted plant is wobbly in the new pot, I suggest using a rhizome clip or pieces of wire to secure it – “wobbly” is not optimal conditions for the plant to root out.

Cutting the spike:

Always cut with sterilized tools. When the blooms are finished, you can cut the spike down to where it emerged from the pseudobulb.