[JLu]

Catts (let's stick to species for simplicity), follow two different growth and bloom patterns. First there is the growth-root-bloom and second the growth-bloom-root.

So a new growth starts: In pattern one, the growth begins (spring) and matures (late spring/summer), roots grow, and then a sheath appears (fall). Usually this sheath will dry and after a rest period (winter), the bud will appear in the dry sheath and bloom in spring.

In pattern two: The growth appears and matures (spring). When the growth matures it produces a sheath and blooms (summer/fall) and then roots grow. So these bloom from green sheaths. They rest in winter.

Since there is a species, unifoliate Catt blooming every single month of the year, these timings must be shifted around slightly.

Bifoliate Catts act similarly. Occasionally, any Catt can bloom without a sheath. It seems to me to occur more often with bifoliates.

There are four Catts that make up the rules as they go: aclandiae, violacea, walkeriana, and nobilior. Their behaviors are more complex.

In your case with aurantiaca, it grows-roots-blooms. So it puts out a fall sheath that dries, rests in winter, and blooms from that sheath in February/March. Thus your observation that it blooms from the second oldest growth. That's not precisely correct, but I can see how you arrived at that conclusion.

As kmarch said, it is impossible to predict the behavior of a hybrid, but after you figure it out, it should be consistent. While this Catt behavior is explained in almost any Catt literature, the best explanation is in Orchid Digest, Oct,Nov,Dec 2004, Vol 68 No.4. This is for sale from Orchid Digest Corp. Since you are so interested in these Catts, I urge you to get some good Catt reference material.