One of these I have not had such good success with is the sweet pea, that requires a cooler climate than I live in.
Sweet peas have a lot of fun colors and different levels of scent. Some can be intense while others, have a fragrance that is barely there.
They aren't perennials per se, but the ones pictured on the left are from my grandmothers garden. Every summer they would come back and creep up her old rusty iron fence. They reseeded themselves abundantly. Happy under the shade of the Aspens and the cool mountain summer nights in the Rocky Mountain Range. Her "Old-Fashioned" sweets were intensely fragrant. I miss those carefree days of working side by side with my grandmother in her garden.