My suggestion is to buy Lois Hole's Perennial Favorites . A little outdated but still a very good reference/ guideline for growing perennials. She also has a book on roses and trees/shrubs.

There is also a book called Perennials for Ontario, but I'm sure it more for zone 5/6.

As well, right here is the best list for us cold zoners. ;)
Ask lots of questions, we have lots of experienced adventuresome 'envelope-pusher' that grow an array of plants that can help you ;)

Sharon

Here is a link that might be useful: Lois Hole's Perennial Favorites

See if there is a local horticultal society .They are very helpfull in where- what does/doesn't grow there ,the plants from hell that no sane gardener would grow in your area as they are invasiveand you would spend the next 20 yrs. dealing with them. Try www.gardenontario.org/site.php/ One I still look to for ideas is The Perennial Garden- Flowers for Three Seasons by Patrick Lima.Has great photos, ideas and most of the plants are able to grow for me. Book is put out by Harrowsmith.They also put out The Harrowsmith Annual gardenby Jennifer Bennett & Turid Forsyth. A good lighthearted read for any gardener that's full of wit trials & tribulations by Midge Ellis Keeble" Tottering in My Garden" it's old 1989 but I still pull it out for fun.