i tried to move two indoor plants outside, on either side of the front door. a parlor palm and a variegated umbrella tree that now seem to be deteriorating. this site gets a lot of direct sunlight in the afternoon. i keep finding conflicting information online about the amount of light these guys can tolerate. what do you all think, are they just having an adjustment period (as some plants do) or will they continue to degrade?
also can anyone recommend tallish plants that do well in pots and lots of direct sun? i'd like to bring them in during winter if possible.
I can't tell you how much sun they can take, but anytime you move something outside you need to adjust it gradually to the higher light levels. Even a plant that can handle full sun under normal circumstances will get badly sunburned if you've had it indoors one day and the next day it's outside in the sun. No matter how bright of a window you had them in, the light intensity doesn't compare to being outside in the sun. So I'd move them to a shady location and gradually introduce them to higher amounts of sun. They've probably been badly sunburned already, so don't be surprised to see the leaves getting bleached out and eventually turning brown and falling off. If you haven't had them out there too long chances are they should recover, but since there's no way to reverse the sunburn on the existing leaves, you'll have to wait for them to put out new growth before they'll look nice again.
Simplified - Chlorophyll is natures sunscreen for plants. It helps prevent photo oxidation (sunburn) and is present in leaves in a linear relationship with the amount of light the leaves receive - the more light - the more chlorophyll - the greater the level of protection.
If you were to move the plant from an indoor location into direct sun, it could easily kill foliage - even young bark tissue. If you do it gradually, by moving the plant to shade first, then to more sun exposure over a week or so, chlorophyll levels will increase, making photo oxidation more unlikely.
If you're interested in what happens: high light intensity levels can cause chlorophyll molecules to rise to a more excited state than normal. If light levels are high enough, the energy that is released as electrons in molecules return to their normal energy state may be sufficient to form oxygen (O- radicals from regular O2. These O- radicals are extremely reactive particles that readily destroy chlorophyll molecules. (This is the same O- radical that causes rapid oxidation in organic molecules when we apply H2O2 [hydrogen peroxide]). Evidence of the process is seen in a bleached or whitish appearance of the leaves.
Unvariegated scheffs will tolerate full sun well in your area, but the variegated plants need protection from midday sun. I don't grow the palms, so I'll reserve comment about their light preferences, but I can say that I agree that you need to either expose the plants to light gradually, or simply site them where you intend to keep them over summer and let the plant take the hit. I have found it's often more productive to move unvariegated scheffs from indoors directly into full sun. The leaves burn and are shed, but the plant replaces them very quickly with leaves that come in already acclimated to full sun. I do this with many Ficus species as well. It's easier than fussing around with gradually exposing them to full sun, only to find the tree shedding most of the foliage anyway because the foliage was unable to adapt. What I'm saying is that foliage on trees grown under low light conditions may not be physically able to adapt to high light conditions, making abscission their destiny no matter how gradually you expose them to light.
Use this strategy only on healthy trees that are known to be able to tolerate full sun.