Frustrated with big Cattelya's

[Nanook 2010]

Have had a few big cats for going on 4 years now and am getting frustrated by the lack of flowering. They are very healthy and growing great, but after producing sheaths on new growth they are turning brown and dying.

I think I am moving them too often....I moved from GA to FL last summer and this year they went in my screened in patio with filtered sun all day. I have since moved them to hang under my oak trees to get them less direct sun

I fertilize once a week with 30-10-30, and like I said, they are all very healthy, new growths and new roots

I've attached a few photos to give you an idea of what I'm talking about

Thoughts?