summers outside-more harm than good?
 

hey guys
i put a lot of my orchids outside for the summer, including stuff that should be sun-loving; all my onc. alliance things, my cattleya alliance plants, dends, cymbs, etc
i have encountered some issues, however
most of the cattleya and oncidium type orchids lose almost all of their foliage during the summers. only a few outright died but it seems futile to put stuff out to build up photosyntate when its used to regrow leaves. since everyone came back in and has high humidity and bright LEDs, they do really well with sending out lush new growth
it gets pretty hot during an RI summer, even with daily waterings it seems too harsh for most stuff. should i only set out the dends and cymbs for summers??

You can't just put even a full sun loving plant directly into the sun after it's been under lights all winter. Plants need a gradual acclimation to stronger lighting. Even my Cymbidium and Catasetum, which spend all summer in full sun start out getting only a bit of morning sun and shade the rest of the day when they first go out. Only a couple of Cattleya species tolerate full sun, and even fewer Oncidium. The day to night temperature swing and better air movement are also advantages that indoor orchids don't get

While certain genera do well in full sun:

• They can only go directly out in mid/late April, and ideally they should go out during an overcast period.
• If you move them out later in the season, you must harden them in shade first (in 1 or 2 steps).
• In the Cattleya group, only Laelia anceps and reedstem Epidendrums can handle full sun. Other species and hybrids should be in light shade (I suggest 35% shade cloth).

I keep C. dowiana, C. trianae, and C. aclandiae in full sun as well, after acclimation. For what full sun in PA is worth.

The "after acclimation" part is the critical piece... moving the plants into increasingly bright light gradually. Similar to people... a day out on a Florida or Hawaii beach on the first day of vacation after spending winter indoors is an invitation to a very painful sunburn. Expose gradually and don't forget the sunscreen (shadecloth?)

"Full sun" is also relative... the number of hours of sun (and intensity) depends on trees, and orientation of one's yard as well as latitude. I learned that the hard way taking Andy's Orchids tags literally... A plant labeled "FS" toasted for me. A trip to Andy's told me why - the nursery has lots of big, mature trees that cast shade at various times of day so "full sun" duration is only a few hours in even the brightest areas. My yard faces east-west, with no trees in the middle. so in summer there's blazing sun from half an hour after sunrise to half an hour before sunset. Even "full sun" orchids get light shadecloth.

i always thought cattleyas don't bloom unless the sun is strong over them, and that oncs were scrubland things from central america that are drought tolerant

"Cattleya" is a big group - now made bigger by genera that have different characteristics. (They're called "Cattleya" but what used to be Sophronitis still like to be on the shady side) My Catts grow and bloom well under 60% shade cloth - more light than that, they tend to burn (but again, that's in MY yard with almost constant sun in the summer) They do typically need to dry out between waterings. I have found that mine do best in wooden baskets where the roots can escape and sometimes grab the wood (think of them as three-dimensional mounts) But that's in my yard, with my watering habits. In plastic pots, many of the big ones can be watered once a week, maybe twice if it's really hot and dry. (Mine in baskets get watered every two days in summer, every three or four in winter) Many Cattleya species grow high in the canopy, but still get dappled light rather than blazing sun. The rupiculous (rock-loving) Laelias of Brazil (again, now Cattleyas) DO take blazing sun in open areas. (Note that the leaves of this group tend to be vertical, so they present the edge rather than a broad surface to the sun)

So, in summary, there's a range... and generalizations need to be tempered by the specifics of a given plant. A hybrid will reflect the characteristics of its component species, which complicates the picture even more. Universally, though, abrupt change is bad... if changing any orchid from relatively low light indoors to bright light outdoors, it needs to be gradual. Spring is a good time to do it, while there is still some overcast and it's on the cool side, sun angle not so high as in summer. At any rate, in general, if an orchid is otherwise healthy and doesn't bloom, more light is probably needed... but gradually and gently.

I think trees are the biggest factor. Most orchids grow in trees as has been stated so any full sun growing orchid will be growing in full sun behind a layer of leaves.

One thing that has surprised me most is how my highest sun loving species tended to develop the most sunburn - could be that they have been young but to me sunlight is overrated. Just seems to stunt them if they get too much.

I am still new to the hobby and I know orchids don't bloom for many people - they always blame light. I would tip more on temperature being the important factor but this is something I still need to investigate more.
One thing I do know is that people religiously blame light levels every time when it could be stress, temperature, humidity and lots of other factors too for their orchid not blooming.

Winter rest is important for those that need it - no rest no flowering but you can bet every last penny that the person in question will be scratching their head, wondering what the problem is, blaming too low light levels.

Could be light levels every time, hopefully I will be able to get a better understanding of this in time myself.

This is definitely a matter of figuring out how much a particular orchid can handle in terms of light intensity under certain conditions (of say outer leaf temperature, ambient temperature etc). A 'particular' orchid can mean type or variety of orchid, as well as size of orchid (size of leaves), as well as whether or not the orchid has been gradually sun-hardened.

If certain days or times of the year come with very intense leaf-burning conditions, then know roughly which times of the year to avoid putting orchids in those areas where the plant could get serious damage.

I don't think anybody here 'rated' sunlight ----- so sunlight probably isn't over-rated by anybody here.

The main thing is to just provide orchids with adequate amount of light for them to grow well (which typically includes enough light to produce flower buds and flowers).

Some orchids can handle really intense tropical sun. Sometimes - even these can get a little burned too ----- depending on the time of the year, but maybe not life threatening. I've seen dendrobium orchids in the wild with absolutely scorching sun - blazing down on them in hot weather ------ they have no problem at all. Absolutely sun-hardened. Their leaves are not always necessarily in 'pristine' in condition though (- which is natural) - although --- some can be in excellent shape. They keep growing and flowering - year after year.

one interesting thing i read is that human eyes cant perceive the intensity of a bulb very well
to us, an old bulb may look bright but still not emit enough light to a plant
ive seen sunburn on some of my orchids under LEDs, so it's evidently a strong bulb
about setting them outside in April: night temps dont even go above 40 till May here, so only the cymbs and a few dends can go out then

No religion here, a lot of observation and some science. First, there's light and then there's light. There's intensity (which can burn plants very easily, watch carefully because it can happen fast) and duration - how many hours a day the plant receives light. And spectrum. An outdoor-grown plant will get the natural spectrum of light, reproducing it indoors can be a challenge. And the whole thing is made more complicated for those growing indoors in higher latitudes, since sun shifts seasonally, at lower angles the higher wavelengths of the spectrum are filtered out by the atmosphere. I can say that with Phals, when I was growing them in the house, I went from essentially no reblooming to about 80% reblooming by adding supplemental light 12 hours a day. (took about a year to see the effect.. other factors such as temperature range stayed the same) Your experience may be different. Experience is the biggie here... observe, tweak conditions a little, observe some more.

Temperature differential is another factor - house temperatures tend to be very even. In nature, even in the tropics, there is significant day-night variation. Seasonal variation depends hugely on location - elevation as well as latitude.

As far as rest... that's another "it depends". I have learned (by killing several plants) that "dry" doesn't mean "bone dry" in most cases (Catasetinae somewhat and some of the summer-dormant Mediterranean-climate terrestrials are exceptions). In monsoonal areas where summers are wet and winters have little rain, there's still dew and humidity. There is a huge orchid-species nursery near me (like about 7000 species, somewhere in the neighborhood of 3/4 million plants) that I visit often (usually leaving significant amounts of cash behind :biggrin:), and have noted that the deciduous Dens, etc. are in the same area as everything else with the same temperature requirements. Everybody gets watered all year. The secret? Nearly everything is mounted, and so they all dry out quickly. Those Dens don't particularly get "rested" but they bloom anyway. (I think the owner, Andy Phillips, knows a thing or two about growing orchids, so I don't judge based on stuff I have read, I observe what works - even if it breaks the "rules" - and try to understand why so I can apply the observations to my own plants. I do know that Andy's plants don't have internet access, and besides they can't read. But Andy has not only years of experience but also the intellectual curiosity, and multiple plants of the same type with multiple microclimates, to experiment. And I get the benefit of all that by observation.)

So in short - it's all about learning the needs of each plant type, then experimenting - even those who live in areas that are natural for some types of orchids are likely to be growing plants that are native to someplace else. So everything we do is a compromise... the challenge is to find that sweet spot where what we can provide is a set of conditions that our orchids can adapt to.

In the reef aquaria hobby, when LEDs first came out people were melting their corals left and right, because they gauged how high to adjust the intensity of the new fixture by how bright it appeared to their eyes vs their old fluorescent or HID fixtures.

It can be beneficial to gather information (if available) or start with just a few plants to begin with ----- and start from some safe (or safer) distance. Start small, and learn/gather information/test ..... before going big.

If some kind of diffuser can be used, then that could help as well.

If you have various light sensing devices (lux meter, UV meter etc), then they could come in handy for assessing light intensity in various spots.

I grow my Cattleya in VERY bright and VERY hot conditions here in Texas. If I moved to RI, I'd grow all of my Cattleyas (mostly species) in full sun. The sun up there is very weak, even during the peak of summer and temperatures are very cool, compared to Texas, Arizona, or Hawaii, all places I've grown orchids. Its all about acclimation, as said many times in this thread.

However, your original post is asking about why your plants dropped leaves in summer. Can you post pics? There are a ton of reasons why this may have occurred, and none of those plants should have dropped more than a few old leaves.

I'm also wondering about the leaf drop. Sunburn usually appears as a white mark on a leaf that may gradually turn brown and die. I have however had plenty of sunburn on my plants without any of them losing all of their leaves. RI is much, much cooler than Philadelphia even in the summer so it's definitely not that it's too hot there. When I first read the title of this post I thought it would be about pests. Was it possible that you encountered some bad bugs that killed off all of your leaves? Mites tend to be the bane of my existence in the summer, especially on high light plants that grow quickly.

mites may have been an issue
i don't have pics of the dropped leaves, and most of the plants have regenerated. are there any threads on this board about acclimating stuff to outdoors for the summer? it seems best to keep things outside during summer
oddly enough, my cymbs and dends don't have any issue going outside in blaring sun without acclimation