There is a great article in the current issue of Tinton's Fine Gardening directly about this topic. Coincidentally, I was scanning through it this a.m. and I recall specific mentions of New Zealand flax (because there was a fantastic picture of it featured elsewhere in the magazine), and Alternanthera (because I was curious about what it looks like).

The article had a table indicating which plants prefer high light/warmth (which, if I recall accurately, include both species you were questioning) high light/cool, and low light/cool (for dormancy). I believe the author also suggests what to do if you don't have enough prime window space for high light/warmth.

I am currently at work, so I do not access to the issue, but perhaps another NJ-ite can chime in. I will check when I get home and post if you don't have an answer by then. BTW, I thought the current issue of FG is particularly great this month.

Well, it's Tauton's Fine Gardening, and here are some answers:

Alternantheras like it warm and bright. Meaning, a sunny indoor windowsill, or 16 hours of high-intensity discharge lighting (on a timer). Water when soil dries out. To keep humidity high, mist frequently, or put plants on top of trays filled with gravel & water.

NZ flax like cool and bright. Meaning 16 hours of high-intensity or fluorescent lights with temps in 40s to low 50s. Water when dry, slowly introduce to direct sunlight in the spring.

The streptocarpella is not mentioned in the article, but as it is a member of the African violet family, my recommendation is to keep in either a window with morning light, or on a table about 3 feet away from the window with a southern exposure. Those are the places I keep my AVs and they do fine. The southern exposure ones sit in the living room, quite happily on a table upon which also sits a bright lamp, which is typically on for a few hours in the evening, for reading and such. Water when dry by filling the dish in which the plant sits.

YourPal, Thx so much! My living room has southern exposure so I'm going to try & bring them all in. The Alternanthera is quite big, I may just try taking some cuttings. I'm surprised that I requires all that light! On it's tag it states light shade, so I had it in a corner of my deck that gets the early morning sun, but is in the shade come the afternoon. It did wonderful. Thx again!