Question
Hi,

I've noticed that some of my Cattleyas that normally produce blooms in sheaths occasionally produce blooms directly from the leaf axil.  Do you know what causes this?  

Thanking you in advance.

Answer
The potential to do this is genetic.  The exact environmental factors that prompt it are not clearly understood.  My guess is that it's  a fuction of light levels in combination with temperatures.  The bud sheath is just another leaf that fails to unfold prior to emergence of buds.  My observation is that this seems to occur mostly when growths are slow to mature and the bud emergence catches up with and surpasses plant maturation. Many Cattleyas are day length sensitive (for blooming), so when day length causes initiation of bud maturation, if the plant has not fully completed its growth, the buds will appear with an incomplete sheath, or no sheath at all.

This entire area of plant development and blooming is very interesting.  There is another condition where, instead of the normal sheath development, two sheaths may enclose the same buds. This sometimes requires a manual opening of the sheath to avoid crushing the buds within the sheath. You may also be aware that some buds emerge from green sheaths and others from dried sheaths-- again a function of the species comprising the hybrid.