Hi containergirl and welcome (although I know you've been posting around for a little bit now)!! :-D

Regarding some ideas - what I tend to do is think in terms of plants that I like and then I look up the cultural requirements and hardiness, and only then do I begin to assess what to do for container culture of the plant.

I think many people forget that when they go to a nursery to buy plants for their gardens, about 9 out of 10 times they buy something already growing in a container. The final 1 out 10 purchase might be a balled & burlaped specimen if they choose to go with a more mature specimen.

In any case, there is a scotoma regarding the fact that most plants that people buy are already containerized and they can't seem to get past the fact that this should mean that the plant CAN grow in a container. Sometimes it boggles my mind when they insist that you "can't" grow a lilac in a container or you "can't" grow a tree in a container. You "can't" do this or you "can't" do that. It's just silly...

But anyway... ;-)

Many of us end up doing spur-of-the-moment or what we dubbed as "PJIC" ("Plants Jump Into the Cart"...LOL) when we buy for our container gardens. Having the internet available makes it quite easy to look up the cultural requirements and find out the hardiness. Then what's left is to right-size the container for the plant (based on size, age, vigor - and this may mean successive potting up for a time), coming up with a planting mix that best matches our cultural practices (usually watering practices), becoming aware of the environment that the plant is living in (amount of sun, wind, heat, cold), and finally, going through alot of experimentation (including many losses amongst the successes) to see the plant through a cold-temperate winter - whether we might find the plant needs protection from actual cold or perhaps (more often than realized) - from excessive moisture during winter.

There are a number of Zone 5 posters, although not all from your area, but consider that you can become a pioneer and inspiration for others just by even giving it a try and posting your results! I have seen container gardeners posting on other forums who don't even realize this or the Container Forum even exist, so there are many of us out there.

One thing I do always recommend is that you check out the other GW or alternate gardening forums just to get some generic info and experiences from other gardeners about a myriad of plants - whether annuals, perennials, shrubs, and trees. That way you'll discover what's actually available and can then fall in love with something, and only then make an effort to grow that plant in a container in your growing space! I'd personally rather do it that way because when you tell people that you are container growing, most times they'll steer you to 99¢ annuals because they don't know better.