Jack, my place gets pretty cold too. Low 30s and an ocassional 29 are the norm here in the winter. Tender plants are near the house and in sheltered locations. Everything else was pretty much selected for being able to withstand those temperatures. I was getting tired of protecting plants in the winter (duranta, tecoma, hibiscus...). According to different sources, a majority of the plants I've planted would be able to survive a freeze down to the low 20s, some could live through colder temps. I know book knowledge and actual happenings are not always the same, but i figured that if I fear for a specific plant, I could always uproot it and place it in a heated shed for the duration of a prolonged freeze (like the 2007 freeze), then replant it the following spring. Good luck with your landscape!!!

Here are pics of my two Dorstenia gigas. I believe I have one each of the two different forms. Form 1 A rooted cutting from Arid Lands. Form 2 A seedling from Out of Africa.

Update: I found my bulb. It is a T4 CFL, 40W, 4100k, CRI>60 by Blue Planet. Assumingly, a 6500k bulb would give slightly higher numbers. Based on some quick measurements, the brightest spot is the middle of the side of the bulb. Which makes sense, because that is where there are the most coils/surface area. Here are my instantaneous DLI measurements with a bare bulb (at the middle of the side): 15.5 @ 3" 12 @ 5" 2.65 @ 10" And with a plastic tub as a 'reflector' (sorry my bulb didn't fit in any of my fixtures with reflectors): 19.75 @ 3" 15.5 @ 5" 4.8 @ 10" And just for curiousity's sake, bare bulb from the top (vertical above plant): 7 @ 3" Of course, the ideal location for your plant is where your reflector has focused the most of it's light. Summary: Plants at 5" away of a 40W CFL in a lamp with a reflector from sunrise to sunset is a DLI of about 10, which is like bright shade. Keep your plants close, as light intensity drops off quickly (with CFLs and all lights). Cheers!

I am here to help if anyone needs it or if you'd like to share ideas that would also be great for all of us! thank you and I hope you visit my channel. Check out my channel about my succulent collection and vlog. https://www.youtube.com/user/asulikeit22