Greenthumbz, those are gorgeous pics! I've heard that there are a couple of trees that are not native to North America but are used by significant numbers of native insects. 1) Malus/Crabapples - native, hybrid, or exotic, Douglas Tallamy's book stated that the leaf chemistry is so similar that North american insects will use all species. This certainly bears true in my experience. I've got lots of crabs, a few specimens and a crazy wild thicket full of them in back,and they are bird magnets, not just for the fruits in the fall but for the nectar and insects in spring and summer. 2) Picea abies/Norway spruce - don't have any personal experience, but was told this by an ornithology student at Cornell who was doing a study on the subject

Thanks for the other tips! I hardly have any shade in my garden, so I'm not sure that the Inside Out Flower or False Solomon's Seal would do so well. Thanks for reminding me about Farewell to Spring. In the Pojar/MacKinnon book they've got a lovely photo of it that I've enjoyed on many ocassion. More penstemons and shrubby cinqefoil are good ideas! Bosky Dell has a seemingly definitive listing of native penstemons: http://www.boskydellnatives.com/description_page%5CPenstemon_spp..htm I get persnickety because they're a bit more loose w/ their native description (geographically) than my anal-retentive aura can embrace. My friend has something with itty bitty pink flowers (clusters) that we've been unable to identify that is in bloom today. We also saw a white single petaled rose in bloom that looked similar to rosa nutkana, but I didn't think we hadn't in Willamette Valley native roses w/ white flowers. Plus, these flowers seemed a bit big, around 3-4" across. And finally, I have to give a shout-out to ceanothus velutinus/snowbrush ceanothus. Fixes nitrogen, fun shiny evergreen leaves: http://www.swsbm.com/Images/C/Ceanothus_velutinus.jpg

Common snowberry would probably grow, provide winter color. Your conifers are likely to be mostly Douglas firs. Salal, Oregon grape, evergreen huckleberry and ocean spray are typical associates on sites tending towards dry. Ceanothus (C. velutinus) and manzanita are found on the hottest, most exposed and/or sandy sites here. Columbia manzanita is so prone to spotting and blackening of the foliage that it is not really a satisfactory ornamental on the whole. There ARE some old ones in local gardens here and there, on rockeries and in other exposed positions. Often when examined up close the foliage is infested. Indian plum is characteristic of floodplains and other places where soils become damp in winter. Red elderberry also prefers it moist and fertile, the lush look of many deciduous trees and shrubs and woodland wildflowers hints at what they want. All occur on sites less than perfect in nature, and can be readily coaxed into growing in gardens made not on sites they would be found on spontaneously using simple tricks like watering a little in summer or planting against a south-facing wall. Going on walks and looking at nearby undeveloped lots, uncleared portions of city parks and other places where there is still natural vegetation and noting what grows where could be highly instructive. Keep soil fertility and moisture regimes in mind, as well as light exposure. You can actually analyze a site using the native plants that are growing on it.

OP might be gone but an interesting report on a BVT X arboreum in Toronto here: http://growingontheedge.net/viewtopic.php?f=2&t=7807&start=255 So, it was dying back in colder winters, but surviving overall...and had a very nice, exotic looking truss. Cross that with the hardiest R. maximum you can scrounge up from the mountains of New England or whatnot...and sure, I don't think a semi-arborescent rhododendron for 5b is out of the question. The issue is as I said nobody has really tried to breed something like that - the goal after the 19th century in rhododendron breeding has almost always been low bushy plants; furthermore BVT, one of the hardiest species, wasn't really used by the pioneering first or 2nd generation of American hybridizers. It wasn't available to them.