My Cattleya's won't bloom

[Rhonda Svoboda]

Hello:
I have 3 cattleya"s that are blooming size and I cannot get them to bloom. I fertalize weekly at 1/2 strength. I give them as much sun short of burning. I water well. etc.
So I am wondering if my grow lights in the fall/winter are the problem.
I put them under grow lights 12 hours a day from October- April. Do I need to fine tune the lights to the natural winter day length? I simply cannot figure of what the problem is. They are healthy and thriving other than blooming.
Should I try to cut back on winter light? The species I have bloom in late winter, early spring.
Thanks

[Paphluvr]

You don't mention what your winter nighttime temperature is. They would probably like to see a 10-15° difference between night and day with the lower temperature being in the mid to upper 50's. Here 40 miles north of Detroit I have no trouble blooming Catts on a rack in my dining room with a southwest facing door-wall, but I drop my nighttime temperature to 58°F.

[SouthPark]

RS - show some photos of your catts - just to see how big they are, and how many bulbs etc.

Maybe also consider the fertiliser schedule too.
Could it possibly be too much fertiliser? What media too?

[estación seca]

Also let us know which ones they are.

[Keysguy]

if they are winter bloomers they probably, in the winter, want brighter light for shorter periods of time, less water with definite dry period between waterings and at least some diurnal temp differentiation although that does not need to be as severe as a lot of other species.

[Ray]

There are several factors that might quash blooming in catts.

One would be excessive nitrogen. "1/2 strength, weekly" is of no value assessing that. What is the formula and how much per gallon are you using?

Another is species in the background, and estacion seca's request for the specific plants nailed that. Some species are "short day" bloomers, meaning they will not initiate blooming until the lighting is shortened drastically for a few weeks. Not all are like that, but it does provide a way to analyze the situation better.