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Warm-Growing Cattleya Culture

This article was provided by Charles and Margaret Baker.
Please visit their web site to find out about their culture sheet subscription service.


This article was originally printed in 1990 in the American Orchid Society Bulletin, 59(9):904-908.



Margaret and Charles Baker

Since their introduction into cultivation, C. eldorado, C. lawrenceana, C. luteola, and C violacea have been much admired for their beauty. These same species have also been the source of much frustration and disappointment to many growers who added them to their collections. Very early in our affliction with the dread disease known as Orchid Specie-itis, we naturally picked a couple of these species as ones we simply had to have. This, we feel, is an offshoot of the talent that enables a person to walk into a shop and go directly to the most expensive item there. With orchids, however, it is usually not only the most expensive, but also the one considered the most difficult to grow.

After diligent effort, we eventually found a Cattleya violacea for sale and made the decision to spend, what seemed to us at the time, the small fortune necessary to make it our own. This in itself was no small decision, because not long before, spending $5.00 for an amaryllis or lily bulb had seemed the height of extravagance. At any rate, we became the proud possesors of a species that we were confident we knew how to grow. It was a Cattleya! Because the cultural instructions for so many species we read about were "Grow like a Cattleya," we had been especially careful to learn exactly what conditions Cattleyas required. We then settled down to wait for the first blossoms to appear. Imagine our surprise when nothing happened. Nothing in the true sense of the word. Not only no blossoms, but no new leads, no root growth, no action of any kind. It might as well have been plastic. In fact, we were starting to suspect that it was plastic when we finally got some action....it started to go downhill. Since we are fast learners, we decided that we were doing something wrong when it finally left us for the big cork slab in the sky.

By this time, we were also starting to have inexplicable problems with some of the other species in our collection. We had been carefully following general cultural requirements for each genera and decided that this information was not enough, at least for all the species in a genera. The answer seemed to be to determine as closely as possible what conditions each species required. To achieve this goal, we researched all the books on orchid species we could obtain, extracting bits of information on each species as we found them. Once we located the original habitat with a relative degree of certainty, we checked climatic records for the area to determine the conditions under which the species grew in nature. We found many surprises. For example, we realized that our chances of success with our dear departed Cattleya violacea would have been much greater if we had grown it like a warm-growing Phalaenopsis. The nightly low temperatures to which we had subjected it for much of the year were down near the all-time record lows in its habitat!

Learning what not to do is an honored and time tested method of education. One that is practiced by many of us. However, it is tough on the ego, tough on the wallet, and particularly tough on the orchids. Also, it is a luxury that cannot be practiced much longer. With the rapid destruction of the world's orchid habitat, with an ever increasing number of species on the endangered list, and with a few species no longer found in nature, we must learn about the plants growing requirements before acquiring a species. Finding replacement plants, if our first try fails, may become more and more difficult. With this in mind, let's take a look at the habitat and cultural requirements of the warm-growing Cattleyas to hopefully make it possible for more growers to be successful with them. Greater success by more growers will help ensure that the species will continue to be available for both species lovers and hybridizers in the future.

Cattleya violacea (H.B.K.) Rolfe. In the past, this species has been know as, and is still sometimes sold as, Cattleya superba. It's habitat covers more area than any other Cattleya. The plants are concentrated in three primary areas between 500-2300 ft. (150-700 m). The first area consists of the tributaries of the Amazon River from near its mouth to the foothills of the Andes west of Iquitos, Peru, a distance of approximately 1500 miles (2400 km). The species has spread south about 400 miles (650 km) onto the Brazilian Plateau, while to the north it occurs about 100 miles (160 km) up the Rio Branco, and several hundred miles up the Rio Negro on the south side of the highlands separating Brazil, Colombia, Venezuela, and Guyana (British Guiana). A second habitat for C. violacea is reported in the foothills of the Andes in the basin of the Ariari River near Villavicencio, Colombia. While a third niche exists along the Paragua River in Venezuela, which flows into the Orinoco River on the north side of the highlands separating Venezuela and Brazil.

This is a large habitat by any standard. Normally, a large habitat indicates that a species is adaptable to many different growing conditions, but this rule of thumb fails dismally in this instance. When climatological records from weather stations near each of the smaller habitat areas are compared with ones from in and around the Amazon Basin, any differences are so small as to seem impossible. It is nearly inconceivable that an area this large has weather that is so much the same, but there it is.

Cattleya luteola Lindley is found in the same habitat as C. violacea to the south and west of Manaus, Brazil. Its range extends to the southwest onto the Brazilian Plateau and westward along the Amazon into foothills of the Andes west of Iquitos, Peru.

Cattleya eldorado Linden shares its habitat with C. violacea from near Manaus, Brazil westward along the Amazon for several hundred miles, and along the Rio Negro to its headwaters in the region where the borders of Brazil, Colombia, and Venezuela intersect.

Cattleya lawrenceana Rchb.f. is found at 1000-1600 ft.(300-500 m) northwest of Manaus along the mid- and upper-reaches of the Rio Branco, a tributary of the Rio Negro. Its range extends westward into the Amazonas district of Venezuela, northward through the Roraima district of Brazil, into the Bolivar district of Venezuela, and eastward into Guyana and the Para district of Brazil. It shares its habitat with C. violacea only in a narrow band along the northern edge of C. violacea's range.

As stated earlier, the weather in this huge area is so homogeneous that the climatic data from one weather station is sufficient to give an accurate picture for the entire area. Manaus, Brazil was selected since it is located near the center of the largest C. violacea habitat area. The temperatures have been adjusted to reflect the difference between the station elevation and the habitat elevations.

The table has been designed for ease of use by growers in both the northern and southern hemisphere. If growing north of the equator, enter the table in the appropriate month at the top of the table and move down the column to determine the average conditions for that month. If growing south of the equator, enter the table in the appropriate month at the bottom of the table and move up the column.

CLIMATE: Station # 82331, Manaus, Brazil, Lat. 3.1°S, Long. 60.0°W, at 144 ft. (44 m). Temperatures are calculated for an elevation of 1300 ft. (396 m), resulting in probable extremes of 97.1°F (36.2°C) and 59.1°F (15.1°C).

F AVG MAX        85   86   87   87   86   85   83   82   83   82   84   84
F AVG MIN        70   70   71   71   71   71   70   70   70   70   71   70
DIURNAL RANGE    15   16   16   16   15   14   13   12   13   12   13   14
RAIN/INCHES     2.3  1.5  1.8  4.2  5.6  8.0  9.8  9.1 10.3  8.7  6.7  3.3
HUMIDITY         75   72   70   72   74   78   79   80   80   81   80   77
DAYS CLR @ 8AM    4    3    2    1    2    1    0    1    1    0    1    3
RAIN/MM          58   38   46  107  142  203  249  231  262  221  170   84
C AVG MAX      29.5 30.1 30.7 30.7 30.1 29.5 28.4 27.9 28.4 27.9 29.0 29.0
C AVG MIN      21.2 21.2 21.8 21.8 21.8 21.8 21.2 21.2 21.2 21.2 21.8 21.2
DIURNAL RANGE   8.3  8.9  8.9  8.9  8.3  7.8  7.2  6.7  7.2  6.7  7.2  7.8



TEMPERATURE: Maintain warm, uniform temperatures all year, with daytime readings near 85°F (29.4°C), cooling to near 70°F (21.1°C) at night. Diurnal range averages 12-16°F (7-9°C) throughout the year.

RELATIVE HUMIDITY: Maintain average values of 70-80% year round.

WATER: Water heavily all year except for 3 months during the winter when a slight reduction is indicated.

FERTILIZER: Apply a dilute fertilizer mixed at 1/4-1/2 recommended strength about once a week when the plant shows signs of active growth. To prevent salt buildup, water equal to 1/10 the volume of the pot should flow through the pot every time it is watered. To remove salts that have formed, flush the pot thoroughly every 3-4 weeks before feeding. This is accomplished by first watering normally and allowing the pot to stand for 30 minutes or so. This dissolves the salt crystals that have developed. Then water the pot again, allowing water equal to twice the volume of the pot to flow through. As an example, a 6 inch pot will hold 10 cups. Therefore, 1 cup of water should flow through at each watering, and 20 cups (5 quarts) should flow through when flushing.

REST PERIOD: Indications of a rest period are not readily apparent from the data in the table. However, plant scientists with the Oregon State University Extension Service have told us that all plants need rest periods in much the same way that we need sleep. In tropical areas where conditions are uniform most of the year, the rest period may be very brief. Kind of a catnap for a week or so. The required rest conditions are probably present during the drier period in the winter. In the habitat, an average monthly rainfall of less than 3 in. (76 mm) can easily be accounted for by one or two tropical showers. However, with high relative humidity levels and overnight temperatures cooling about 15°F (8.3°C), some moisture is available to plants growing in the area in the form of dew. During the winter, these conditions can be simulated in the greenhouse by a good watering every couple of weeks, with light mistings applied every few days. Fertilizer should also be reduced to an application every 2-3 weeks if the plant is not in active growth.

GROWING MEDIA: Plants usually perform well when grown on cork rafts or slabs, providing high humidity levels can be maintained. If pots are used, unglazed clay pots seem to produce better results than ones made from plastic; but in either case, the medium must be open and fast draining. Either medium-coarse fir bark or cork nuggets produce good results. Some growers feel that these plants are not as healthy or vigorous when tree fern is used.

Armed with the climatic conditions in the habitat, we should be able to successfully grow these species. At least we know what basic requirements need to be met. However, there are other factors that come into play. If climate were the only consideration, we would expect all of these species to be found over the same area, since the climate is so homogeneous. Such is not the case. Both C. luteola and C. eldorado are indeed found with C. violacea over all their range, but this is only a small portion of the range of C. violacea. On the other hand, C. lawrenceana, which has the same climatic requirements, shares habitat with C. violacea in only a very small portion of its range. The big question here would seem to be, "Why?"

This question was possibly answered, at least in part, by G. C. K. & E. Dunsterville in an article, "Blackwaters, Acid Rain and Blackwater Orchids" that appeared in the May-June 1983 issue of Orchid Digest. The focus of the article was the blackwater region in the highlands of southern Venezuela, where C. lawrenceana is found. The rivers in this region are very acid, with pH readings as low as 3.0 in some areas. In addition, several scientific research teams have gone into the region, which is several hundred miles from possible industrial pollution, and measured the pH of freshly collected rainfall samples. Inexplicably, the tested samples all fell into the range of pH 3.5-5.0. To put this in perspective, household vinegar has a pH of about 5, blueberries, one of the most acid loving plants, prefer to grow in soil with a pH of 4.5-5.0, and rainwater normally has a pH of slightly below neutral (7.0) to as low as 5.5 in areas removed from industrial contamination.

Also in their article, the Dunstervilles were puzzled by the difficulty they have maintaining epiphytic orchids from the blackwater areas at their Caracas home. They indicated that the orchids seldom lived for more than a few years. They stated that the Caracas water supply, which they use to water their plants, is on the alkaline side with a pH of 7.0 or greater and speculated that the plants might perform better if more acidic water could be used.

Hopefully, people knowledgeable in plant and soil chemistry will eventually be able to shed more light on the subject of specific requirements of orchid species from the blackwater areas. In the meantime, if these warm growing species from in or near the blackwater areas are performing well in their current growing environment, leave them alone. In effect, if it ain't broke, don't fix it! However, if the plants are not performing as well as they should, gradually change their conditions to those indicated by the climate data. If further change seems necessary, try increasing the acidity of the growing medium by adding sphagnum moss or redwood bark or by using a more acidic fertilizer. It would seem that we are armed with at least most of the factors necessary for success with these species. Now it is simply a matter of fine tuning the conditions until the right combination is found for each particular growing environment.

          Charles and Margaret Baker, Portland, Oregon, USA
Email <cobaker@troymeyers.com>    

    Orchid Species Culture web site  http://www.orchidculture.com

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This article was provided by Charles and Margaret Baker.
Please visit their web site to find out about their culture sheet subscription service.