In blue cattleyas there is observed a phenomenon defined as instability. This is the blooming of a blue-tepaled form lacking or nearly lacking any blue coloration in the sepals. The appearance or non-appearance of the blue is sporadic from year to year. In its strict sense, therefore, stability is when the blue color reaches its potential whenever the plant is in bloom, with only minor differences relative to the environment. Stability, however, is also applied in breeding to mean having sepal coloration every year, though ignoring the fluctuation within it. We are here concerned with stability in the strict sense.
It is better to approach this discussion by separating these unstable forms into white and lavender sorts. Most of the hybrids fall into the lavender sorts, while most of the species fall into the white sorts. The white sorts are blue-tepaled under near-perfect conditions and have a good medium-blue color. The lip is a darker blue. There is more coloring on the lip under these conditions, also. The lavender sorts, under near-perfect conditions, have a slightly darker blue color than the white sorts and the lip coloring is affected less. Lavender is barely apparent in the flower.
It is reported that the species in their own environments have flowers which are much bluer than when grown in greenhouses. Further study of the plants has shown that when grown under cooler conditions than normal, more blue color develops.
The workings of the blue color seem to be determined in part by temperature. Where the temperature is above a critical point, little color is produced in the white sorts. In the lavender sorts, the blue color is apparently channeled into the production of lavender. Because of these factors, stabilization may be difficult to attain. Holding just a small bit of lavender in the hybrids may help. Selection of progeny that are of a good shade of blue, even when grown warm, may be an approach. Polyploidy may also be of value.
We can breed blues much like our existing ones with little difficulty. Providing a wide range of size, shape, and season is in the very near future. The color, however, needs to be made more distinct; it needs to be enhanced. Enhancement is being approached from what is considered to be co-pigmentation. A good example of what happens is seen in some of the blue species. Where the blue veining of the lip overlays the eye-color area, different colors appear. If the eye color is of an orange nature, maroon is the outcome. If the color is a lemon-yellow, the result is a very dark blue.
Since the blue color is very recessive, what criteria must we consider for the enhancement parent? First, it must be the proper lemon-yellow to green. Second, the color must not be overpowering, but must bleach out or be somewhat recessive when bred with labiate cattleyas, especially. Third, it must have little genetic material to produce lavender. (White and white-with-colored-lip cattleyas, as a general rule, have genetic material for lavender.) Fourth, it should be a diploid, especially if any further breeding is to be done. (The blue cattleyas are presumed to be diploids.)
One of the plants that fits the above criteria is Brassavola digbyana, and several hybridizers are using it. The one major "unknown" is whether or not enough of the green will be present in the progeny for enhancement. It is definitely felt to be a step in the right direction.
Some fine colored blues (along with several lavenders) have resulted from using Epidendrum mariae crossed with Laeliocattleya Blue Boy, but Lc. Blue Boy with Blc. Ojai is producing lavenders.
The first generation of any of the hybrids utilizing blue with "other" colors can be expected to be in the lavender shades, with some possibly having blue casts. However, selfing and/or back-crossing to blue can be expected to give some blues, of which there may be enhanced ones.
Stabilization and enhancement are two main obstacles in producing good blue color in Cattleya. Time, patience, and careful observation will, hopefully, achieve the desired results.
(American Orchid Society Bulletin, Vol. 39, No. 4, April, 1970, pp. 343-344.)