ok some
plants are perienials and don't bloom the 1st year.so you'll want some annuals to fill in the gaps.if you check with other canadians....you can find out some re seeding annuals for your area so will just pop back every year.
you didn't say WHAT type sun bed gets.(but know not TX hot sun....)
I'd till the bed looseing the soil before adding the
plants like compost and manure& mushroom compost.that way they healthy& grow good.
hard for me to think of hardy stuff for ya cause most IS hardy for me.
Mums are nice& are some sub-zero types now(they waited till I moved to develope those)
(BES) black eyed susans.is a wild
flower,but looks great
Coneflowers..come in colors and angel a white one smells
clemtris vine grows well.
and have seen monarda bee balm.its red.
I'll go veiw my HGTV garden show tape of canadian gardens and fill ya in more.
Catmint would be nice,but I love catmint.I like salvia too but hear
zone 5ers complain about overwintering it.but are annual ones(well guess all would be annuals for ya almost)