Tonight we are supposed to go down to -2C which will definitely be the end of the annuals. Even without frost, they stop blooming when the weather gets cool. I went out yesterday and gathered up the bits and pieces that were left so we could enjoy the blooms a little longer.
The purple salvia might have withstood the frost but I picked it anyway as well as the magenta asters which are perennial.
The fibrous begonias did extraordinarily well this summer, and are still blooming their little hearts out. I left quite a few outside just on the off chance that the frost skips them.
At the end of the spring season when things are on sale, I bought a dwarf reblooming lilac (Bloomerang), and planted it in one of the few sunny spots in our yard. It responded by setting a few buds even this first year. I'm looking forward to next spring when it will be able to bloom in full force. It's supposed to bloom profusely in the spring, then rebloom more lightly in the fall. So here's hoping it lives up to the hype. Mature height is about 5' which makes it a good candidate for smaller gardens.