Questions about light.

[Cantando]

Here are 3 questions:

1. How dangerous is a few hours of direct sun to most orchids?

2. I have heard that keeping orchids under a flourescent light 24 hours a day will mess up the plant's natural "clock" or something and not do much good. Any truth to that?

3. I keep my orchids by a large south-facing window that gets pretty good light and a few hours of direct sun most days. Does it take a lot more than this to encourage growth?

[jerrymeola]

You do not need much light for orchid growth but every type of orchid has an optimum amount of light it needs to flower. Young plants can be grown in quite low levels and often it is preferred to do so.

Paphiopedilums (Lady Slippers) 900 foot candles to flower
Phals want 1500 foot candles
Oncidium 2500
Dens and Cattleya 3500
Vanda 8000

Almost any orchid can take a few hours of sun even Paphs. I grow in much higher then recommended levels and accept a few burn leaves as payment for more than normal amounts of flowers.

[mayres]

As jerry has noted, it depends upon what kind of orchids you are trying to grow. I have fried (dead) a phal in a NE window ledge with just two days of morning sun. Other types of orchids in the same window do fine. Yes, 24 hours of continuous fluorescent light is undesirable - I have mine on 16 hours a day except reduce to 14 hours during late fall to mid winter. Seems to work great. I put my high light requiring plants outside for the summer on the east side of my home and the amount of direct light they get in the morning hours (till approx. noon) was enough to bloom any/all of them. mike

[Maddy]

The test is to see whether or not the leaves are getting hot. If they're getting really warm to the touch, be careful. I have some of mine under a grow light, but the rest range between a south and west window.

I haven't killed any of my orchids with too much light, but I fried an anthurium over the summer putting it on the back porch for a little sun...

[Cynthia, Prescott, AZ]

As Maddy suggested, feel the leaves. It is the heat that does the damage, not some mysterious rays. Plants that don't burn but are in too much light for their type will be under stress and eventually secumb to desease or wither away.