In article , Rob Halgren
wrote:

I have a smaller catt that does that and I have not had it long
enough to see anything else from it, so I thought it was just
normal for the cross. We need some good ideas of how to prevent
it. Are they getting more light than they need? So that there is
not 'reach' in the spike growth?
SuE
http://orchids.legolas.org/gallery/albums.php


I think that is probably different, and you might want to wait until
it blooms next year to get rid of it. I get the distinct impression
that if all your cattleyas did that over a period of several years, it
has to be cultural. And frustrating...

So, some more questions... Did they just put up a street light
outside your greenhouse? More traffic? New glazing on the windows? I
don't know why I think this, but I suspect that disrupting the dark
period might result in something similar. It doesn't take a whole lot
of light for a plant to think it is daytime (even if it isn't enough to
actually support photosynthesis). My guess for today (it will change
tomorrow) is too much light - at the wrong times, that is.

I love a mystery as well as the next person, and I've spent a couple of
hours trying to research this in my orchid books, and there are
absolutely no mentions of this symptom. From what I've read, though, if
you had too much light, you'd see that reflected in the leaf
color/health. And the fact that the plants are setting sheaths says
that they are inclined to flower. Perhaps it is another environmental
condition: not enough light, pollution, degradation of potting media,
etc.

If ALL of your orchids are experiencing this malady, it might be an
idea to do an experiement in light, room environment, loaning a plant
to a fellow orchid grower to see what happens, etc. It certainly sounds
like a frustrating situation. If you were in my area, I'd be happy to
swap plants with you to see what happens.