Greetings, folks!
Since my name came up here and this is a subject that interests me a great deal, I thought I'd give a brief summary of my experience so far this year.
Yes, I can grow highlanders, alpines and some lowlanders outside year-round in full morning sun, dappled midday and afternoon sun, and produce absolutely gigantic (>10 m lianas)plants.
This year, I reworked my back garden and put out a "full sun" wooden high table for Heliamphoras and Nepenthes at the beginning of the year when sun angle was lower, and temps dipped every night into the high 40s/low 50s F. Everything appeared fine until early April when I started to see some sun stress in certain plants. We had an extraordinarily warm, subhumid and bright dry season (Dec-April)this year and, having spent a lot of time working in that part of the garden, can assure readers that the sun was a real scorcher for the later part of the summer, even with SPF 45. I'm at 1,600 m, so elevation has a real impact on burn capability.
Plants in trial that burned rather severely included young rajah, older spathulata, bongso, lowii and "black" singalana. All of these plants had been grown previously with very high light conditions and 15% shade. A very large (1.50 m diameter) highland truncata that had never shown any sun stress and was NOT moved did develop large bleached patches on the leaves that have only now started to recede.
Plants in the trial that showed little or no stress include medium rigidifolia, large petiolata, small platychila, small argentii, small epiphiata, small ovatas and very large muluensis. The rigidifolia has responded to the move by producing very large leaves with extremely heavy substance.
I did not attempt to try any of the spp. that I know to favor shady conditions, but I am seeing much better growth in some of these spp. (hamata, aristos, macfarlanei, pilosa, etc.) since I increased light intensity by pruning tree shade marginally.
The rains came with a vengeance in late May (by yesterday we had already exceeded 40% of average total precipitation) and days with very bright mornings followed by 8-10 cm of rain and resultant 1000 % humidity makes for very happy Neps. Cloud cover every day at midday has also shielded the plants from a sun that is now almost directly overhead, but light is very, very bright even when cloudy.
Need to find a new photo dumpsite to add some images to this. Apropos this subject, I have a great pic of a huge old red alata that has climbed up and out of the shade cloth covered atrium downstairs, through the wrought-iron grid and onto the patio where it's elongating and pitchering beautifully right on the concrete beside a huge old mamillaria cactus and receiving nuclear burst-intensity sunlight all day long with nary a red spot on its leaves.
Hope this was of interest,
SJ