Basic Question about Light Through Windows

[HiOrcDen]

Hello all.. I would just like to get an idea about how safe my Orchids will be in sunlight through a nearby window. For low to somewhat high (not full sun) light requirements, what is a safe yet effective range from an unobstructed west facing window? I have a range of spots from right upon the window sill to about 4 feet to place them. Could this be a safe and effective range? The light requirements for my most light loving plants is about 2000+ f.c.

Perhaps, to simplify my question, would a Phalaenopsis be safe right upon the unobstructed western windowsill?

[Ray]

Originally Posted by HiOrcDen

Perhaps, to simplify my question, would a Phalaenopsis be safe right upon the unobstructed western windowsill?

I suspect not. You're probably better off a foot or two back, at a minimum.

Keep in mind that to plants, light coming through a window (or greenhouse covering) originates at the glass, not the sun. In effect, the light isn't transmitted through the glass, but is absorbed and reradiated.

I have a greenhouse window in my kitchen that I use as a blooming plant display case. It faces directly east and is shielded by large trees and the two-stories-on-pilings house next door, that is only about 20 feet away, so morning sun exposure is quite short, yet I can get burning in phals, if I'm not careful.

[Dimples]

I don't even put my phals in my unobstructed east windows without a sheer curtain, and east is generally considered the "safest" window for direct sunlight. In summer the window will get 5+ hours of direct sun and that's too much for all but the most sun-loving plants.

[Roberta]

Feel the leaves - if they are warm/hot to the touch move them immediately. You will need to check whenever the light seems even a bit direct - and remember, the sun shifts so what may be OK last week may toast plants next week. So until you have seen the plants through the range of seasons, you need to stay vigilant.

[estación seca]

There is no upside to direct sun on a Phal. leaf.

Most hybrid Phals don't ever need sun shining on their leaves. They flower better with lower light levels, around 1,000 foot candles. They do want a nice long summer sunny period of nights less than / days more than 12 hours to flower well.

The one species Phal. pulcherrima (formerly Doritis p.) is the exception. It grows in full sun on rocks in Thailand. It was used extensively in hybridization to get the dark pink color into the round-flowered Phals, so some of the dark pinks tolerate more light. But they don't need it. These pinks were at one time in nothogenus Doritaenopsis, but Doritis was sunk into Phalaenopsis.

[The Mutant]

Originally Posted by Dimples

I don't even put my phals in my unobstructed east windows without a sheer curtain, and east is generally considered the "safest" window for direct sunlight. In summer the window will get 5+ hours of direct sun and that's too much for all but the most sun-loving plants.

Same here. I only skip the curtains during autumn/winter, but during spring/summer the Phals would get too hot.

[HiOrcDen]

Originally Posted by Ray

I suspect not. You're probably better off a foot or two back, at a minimum.

Keep in mind that to plants, light coming through a window (or greenhouse covering) originates at the glass, not the sun. In effect, the light isn't transmitted through the glass, but is absorbed and reradiated.

I have a greenhouse window in my kitchen that I use as a blooming plant display case. It faces directly east and is shielded by large trees and the two-stories-on-pilings house next door, that is only about 20 feet away, so morning sun exposure is quite short, yet I can get burning in phals, if I'm not careful.

Originally Posted by Dimples

I don't even put my phals in my unobstructed east windows without a sheer curtain, and east is generally considered the "safest" window for direct sunlight. In summer the window will get 5+ hours of direct sun and that's too much for all but the most sun-loving plants.

Originally Posted by Roberta

Feel the leaves - if they are warm/hot to the touch move them immediately. You will need to check whenever the light seems even a bit direct - and remember, the sun shifts so what may be OK last week may toast plants next week. So until you have seen the plants through the range of seasons, you need to stay vigilant.

Originally Posted by estación seca

There is no upside to direct sun on a Phal. leaf.

Most hybrid Phals don't ever need sun shining on their leaves. They flower better with lower light levels, around 1,000 foot candles. They do want a nice long summer sunny period of nights less than / days more than 12 hours to flower well.

The one species Phal. pulcherrima (formerly Doritis p.) is the exception. It grows in full sun on rocks in Thailand. It was used extensively in hybridization to get the dark pink color into the round-flowered Phals, so some of the dark pinks tolerate more light. But they don't need it. These pinks were at one time in nothogenus Doritaenopsis, but Doritis was sunk into Phalaenopsis.

Originally Posted by The Mutant

Same here. I only skip the curtains during autumn/winter, but during spring/summer the Phals would get too hot.

Cool, thanks all. So I understand that sometimes ‘full sun’ Orchids really could do with a little bit of shade, like maybe 30% shade cloth. If this is correct, would a full sun plant still not tolerate the window I described?

I have a Begonia which is supposed to be grown in shade. I have it on the same windowsill literally an inch from the window, and it’s stayed in perfect condition and grown rapidly.

[Ray]

The “full sun” plant would certainly be more appropriate, but don’t forget that a plant’s light needs are a combination of intensity and time, so such a plant may do fine with the exposure intensity, but might not get it for enough hours in a day.