Acclimating plants to higher light

[Maru777]

Hello everyone! I again need a bit of advice. I have a few cattleyas that after doing some research like more light than they currently had where I was growing them (an Eastern looking porch screened with mosquito net). So I have decided to move them on the other side of my house on an open balcony. February is the coldest weather I’m going to get here - which is really not saying much (today this means 29C / 85 F). But still, I figured now is the moment to move them, since it’s not getting any better. This will be the first time I am trying to move them into more light though and I am a bit worried I will get them burned so looking for some advice on acclimating them to higher light levels. To give you more info on the actual light they are moving from and to - on the screen porch they got about 2,500-3,000 FC in the morning for about 3-4 hr and in the new place I’m looking at about double that also for about 3 hr, but in the afternoon. Temps will be the same since - still outdoor. I tucked them behind a column so they only get light on them as late as possible in the day but it still seems to hit 6-7,500 FC at its peak. They should have a nice breeze. I only tried it with 3, a catt loddigesii, a no id mini catt and a renanthera kalsom. The renanthera is in SH the others in bark. I’m now panicking and checking on them every couple of hours how long will it take to see sunburn damage if it is too much for them? Should I move them inside for part of the afternoon? Sigh! I love experimenting but I stress too much when trying something that can damage the plants. Thank you!

[Roberta]

This is a good time of year (in the northern hemisphere) to move plants to areas that get more light... sun angle is still fairly low. As we approach the equinox, the midday light becomes more intense - but that gives another 6 weeks or so of gently-increasing sun intensity before we get there. (I have toasted plenty of leaves around the vernal equinox when the sun suddenly cleared the house... surprise!) If there is good air movement, that helps too. If you want to check on them at times of the day where they may be getting strong sun, just feel the leaf... if it is hot to the touch then sunburn is possible. (That would mean that the leaf temperature was a lot warmer than you are) If the leaves don't feel hot, they're fine.

[estación seca]

I think your eastern porch should have plenty of light for them if it gets a little direct morning sun. Does it? I live farther north than you, but still south of most of the US, and I can flower Cattleyas in bright summer shade. If you're unhappy with their growth on the east patio I would look for other causes, unless the patio is very deep and the plants never get any morning sun.

The Renanthera should be able to grow in full, all-day sun in your garden year-round if you acclimate it, and water it every day. These are some of the highest light requirement orchids. People in south Florida told me they won't grow and flower well without at least 4-6 hours of direct sunshine, and more is better. They plant rootless tip cuttings into Florida sand in full sun and water heavily.

I have a small Renanthera coccinea seedling. It is potted in a net basket with sphagnum moss. I put it right next to a southeast facing window where it gets about 4 hours of direct morning sun. It is happy, even when I forget to water it. It is too cold to be outside here now.

I also have a tiny Renanthera Kalsom, in a small net pot with a few large chunks of bark. It is in a different part of the sunroom, where it gets a little less light. It gets watered daily from an automatic spray system. I've been worried about giving it too much light because it is so small. Now that I've seen how well the slightly larger coccinea does in the window, I'm going to move it next to the window. It has hardly grown in a year.

[Maru777]

Reporting on progress The Eastern porch gets some sun in the morning but I have some trees that partly shade it (that I am trying to get rid of) so I needed a bit more light. The catt Fire Dance for example is blooming with no problem in that light (growing buds right now) but these 2 catts I moved just don’t want to, thus my experiment. So far I had to move them a bit around the balcony so that they get shaded for longer because strangely out of all of them the Renanthera got a bit of sun burn. Not a lot, thankfully as I was monitoring them almost non stop - just a bit on the lowest leaf. I moved it as instructed when it felt hot to the touch but the next morning there was a bit of sunburn already on it so I might have checked it a bit too late. All good though, all the other leaves are doing well and no other sun burn since I changed their position. I was surprized that it was the Renanthera that got the burn and the catts were peachy even though light requirements are flipped but I think it’s because the Renanthera is still technically a baby (though bigger than both the other ones) while those are mature plants. The sun burn baby is growing a new leaf and root but it’s always doing that so can’t yet tell if it likes it better. Clearly it does not dislike it since it’s still growing. The no id catt has a new growth too and the fussy remaining one is doing absolutely nothing but at least not declining either I am curious to see if the catts bloom here and also to benchmark the Renanthera against its “twin” that I have kept in its original place.

[Roberta]

Renanthera not really a high-light genus. Not as much as Vandas. So what you observed is not uinreasonable... probably just a case of a small blast of sunlight on a surface that was horizontal so got for a bit longer. Note that a lot of Catt leaves are at least somewhat vertical... certainly not all, but many use that "strategy" to protect from strong sun.I have, however, managed to toast Catt leaves, but it does happen more on plants where leaves are horizontal.