What native north and south American annuals are suitable for hanging baskets and window boxes in Toronto. An examples that I know of would be portulaca, zinnia, and begonias.
Thank you for contacting Toronto Master Gardeners.
Window boxes and hanging baskets can hold a great number of different annuals. As you are not wintering over the choices are only limited to what is available at your local nursery.
You do need to take into account is where the baskets and boxes are located. The ones in shade will require different annuals than ones in full sun. When looking at the plants at the nursery it is important to notice light requirements and drought tolerance. With baskets and boxes you will find they dry out very quickly in the heat of summer. You will need to monitor them closely and water very frequently, perhaps daily or twice daily. if you pick annuals that have some drought tolerance your job will be a bit easier and the plants more forgiving.
Our library is full of articles on choosing and growing annuals. I have attached two below that go through many of the common plant choices. These should give you an idea of what is commonly available her in Toronto.