Check this post out, there are my posts about Wash. Robusta not growing 30 miles south of Columbia, SC (click the link below). Here is a link that might be useful: Click Here

So,the answer to your question is some thing like this,for one thing look up Iowa palms he discribed what he did allthough probably not in enough detail for your needs,I don't know how far he spaced his lights out but I do know he used c-9 x-mas lights(the smaller bulbs)also it reached beyond -10F where he is.I am going to try the same thing on my washys this winter only with rope lights,I put a thermometer on these balled up and it reached 90F plus,it will be much colder outside than it was inside,as far as how close your palm is to the house I think that will help more than it hurts for a few reasons,added warmth for the roots and leaves protection from cold winds and should be easier to wrap when palm gets above roof line(positive thinking!)So you first need to mulch at least 6" up trunk and around root base and cover trunk with something like burlap or something that does not hold moisture would be better,I would also add remote sensor at base and top where fronds come out so you cam monitor temp first year at least so you get your technique down,don't put thermo right next to bulbs or rope lights.I would rap with "burlap"from base to at least a foot above newest leaf so sun does not burn leaves thru plastic,wrap with lights,I don't think they need to be overlaping a whole lot maybe 2" or 3"wrap it to the growth bud,you don't need to go higher,then cover with house insulation,maybe 8"on all sides you can just pull some out of your house haha-wrap off top,you should open when temps warm to 50 or above so it does not bake,you will need to turn on lights anytime temps go below freezing,oh yea before you do all this spray the growth bud trunk and base with fungicide and let dry completely.You probably know to cut all but the newest leaf after cold weather zaps them,or even better right before if you know its coming so the bud is not damaged,open up in early april or so,don't let the spear get wet and cold in early spring.All this sounds like a lot but typing it all is more time consuming for me!

Its been a little bit of time since I last spoke of my palm. I just want to provide a status update: My little Robusta is now doing excellent! Its completely reinvigorated itself and is striving. It gets larger everyday. The single leaf it had, has grown very large indeed, and seems to still grow. It even has sent out another leaf from the bottom of the "trunk". Its still tiny yet, but seems to be going haywire with growth. Its still in the bay-window that faces the South/Southwest. It gets sunlight when we have a sunny day, and now our furnace is on so it pretty much stays at or around 73F all the time. Its a nice green and a lighter green at the bottom where the leaf continues to grow from. I just give it a healthy dose of water and have kept it moist. It struggled somewhat in the beginning. But it seems like once I put it in the window with the furnace heat and consistent sunlight, it really took off. I don't water it too often, only every 2-3 weeks I'll drop some water in there to soak through to the bottom. Looking back now I can't believe I was ever worried it would grow! It seems to be pursuing relentless growth and is thriving so very well. I still worry about a little since we're heading into Winter (here in NW Ohio) and our sunny days will become ever more limited with each passing day. Even now, some days we have the sun doesn't even bother to come out. While other days we'll get some partial sunshine, and the occasional day where its full-sun all day (abundant in summer, but not too common in fall/winter). The El-Nino this year, hopefully will provide a messed up weather pattern. That may provide an abnormal level of sunny days this Fall/Winter. Here in Toledo, Ohio I've read on average we get 200 cloudy days though-out a given (average) year. My Robusta is after-all in the bay window, so it still gets the ambient light even on an overcast cloudy day, just not full-sun like in California, Nevada or Florida. I hope it can at least survive the Fall/Winter on what light it can. Once Spring gets here most everyday is sunny until Fall comes back around. When its sunny out it gets full-sun most all the day. It hasn't seemed to mind so far it seems. Its growing more each day it seems! Lately we've had one day cloudy, and the next sunny. So I don't think it even minds yet. Do Washingtonia Robusta go into a dormant state (or I guess like a coping state) during periods of low sunshine, such as Fall/Winter? Or, do they pretty much expect Full-sun everyday, even in Fall/Winter? Can they survive with days of no sunshine (light from outside, such as cloud-cover days)?

Its actually a pretty big container. I'm not sure how many gallons it would be considered. But, its decently heavy as well. Its does hold water for a pretty good amount of time. When I potted it I mixed together generous amounts of Perlite, Sand, and Miracle Grow "Cactus, Palm, and Citrus" potting mix. That was the medium I came up with. The container has 5-6 drainage holes on the bottom to drain into a tray. Here is the container: