blomma wrote: There are several varieties of Buddleia, and many varieties of roses. In both not all are hardy in the North. Since it did not survive Buddleia Flutterby 'Petite Blue Heaven' was not hardy.
B. davidii is hardy to zone 5, yet i grew it in Zone 4 from commercial seed. I kept them for 3 years, then gave them away for I needed the space. They are perennials and don't grow as an annual. Height 6-8" in one season. They flower on new wood the first season from seed if stated early.
I have 9 rosebushes, all Floribundas that blooms all summer with a short rest in between. I also grow 6 mini roses. All are hardy to zone 4. They too flower on new canes so they get trimmed back in the Fall so that snow don't break the canes and the canes don't get whipped around by wind. This year I needed to thin out canes in the center to keep it open for maximum air circulation. I have had the same rosebushes since 2004. All got a drastic pruning to 1".
We had a extremely cold winter of 2013-14. Went down to -30 below during many nights. Not one rosebush was lost to winter. Even more surprisingly was that they bloomed up to October this year. Had more buds but we had temps of -10 which killed the buds and sent the plants into dormancy.
Roses have to be purchased according to their hardiness. With reasonable care they will survive in colder climates. I can't grow Hybrid Teas. and Grandifloras since they are not hardy for zone 4.
Valal The 4th photo are all Gaillardias. They are hardy perennials and come up every year to bloom all summer. They hold down the soil the reason my daughter allows them to grow at will. She is also in zone 4.
If you want to mulch wait until the ground is frozen. You don't want to keep them warm, which can't be done in your zone anyway. You want to keep the soil from thawing and freezing (heaving) for it is that which tears roots and kill plants that are not established yet. Mulching after soil is frozen will prevent that. On established plants mulching is not needed unless to keep weeds down. Newly planted perennials can benefit from mulching since their roots aren't established if planted late in the season.