In zone 4 you may not be far from me here in Cache Valley. I have two of those you're talking about:

1) My mom loved lilacs. I haven't planted any because of the short blooming season and general untidiness of them, but probably will this spring in her memory.

2) My mother-in-law was born in Hawaii and loves bird of paradise flowers. She has told us all that at her funeral that is what she wants. Can't really grow them here as far as I know, so never tried.

Thanks for nice thread.

My beloved grandmother's name was Pansy, and I always plant pansies in a planter in the spring. Her real love was roses. I have a few rose cuttings from her home that the current owner of her home graciously allowed me to have last year. They are struggling on my window sill, but are still alive. They won't live outside in our zone 4 climate, I'm certain, as they came from a much warmer zone 8. But, one of these days when they're big enough to take cuttings off of, I will try some outside.

My Mom and her Dad (My Grandpa) both loved roses. @Linda, you may be able to graft your roses to a hardy root-stock, check w/ your local extension office about how to do it.

My Dad was more a veggie and fruit tree grower, not so much anything ornamental; unless it was a sapling from the mountains, like an Quaking Aspen, or a yucca offset from the desert. His mother also had quite the rose garden.

Plants that I particularly remember from my childhood are:
Iris, Tulips, Forsythia, Cherry, Peach, Apple, Peonies, Hens-N-Chicks, Yucca, Red-Leaf Maple, and of course, Roses.