After figuring out your light and soil conditions, and a colour scheme, you should have a manageable number of pollinator plant options. Now look at bloom time. Aim to have flowers blooming from early spring until fall to provide pollinators with a constant supply of food.
Achieving continuous blooms
To start, choose 3 to 5 types of flowers for each season. Since each plant blooms at a slightly different time, and for a different length of time, chances are they’ll overlap and provide continuous flowers. However, it may take a few years of observation, and some trial and error to achieve continuous blooms in your pollinator garden. The more kinds of flowers you grow, the easier it will be to attain continuous blooms.
I have found it difficult to plan bloom times more precisely than that. I wish I could find a week-by-week list of what’s blooming when in Ottawa, or even in Ontario. I have tried using the Minnesota Wildflowers What’s in Bloom? by month pages to get a rough idea of the sequence of blooms for native plants.
In my garden when there’s a time with few flowers, I visit other pollinator-friendly gardens, like Fletcher Wildlife Garden or Maplelawn Garden, to see what’s blooming there.
Bloom time will vary depending on how much sun a particular plant receives. Let’s take Anise Hyssop as an example. I love this plant because of its strong structure and long bloom time. I have the same kind of plant, grown from the same seed that blooms earlier in a part-shade location, as opposed to full sun. Seedlings start blooming a lot later than mature plants. Also, the sterile cultivar ‘Blue Fortune’ blooms much longer than the straight species because it isn’t putting energy into producing seed.
By choosing a variety of flower shapes, you’ll provide texture and interest in your garden, as well as feed different types of pollinators.
I use a table with the 3 seasons along the side, and flower colour along the top to sort these variables. I plug in possible plant choices to make sure they’re evenly distributed. For example, I don’t want to end up with all of my white flowers in spring and all of the yellow flowers in fall. Add or change plants as needed.
I recently found a different style of chart to track bloom times and flower colours in a pollinator garden on Annie White’s PollinatorGardens.org site. (Annie White is a well-known researcher studying the value of native plant cultivars to native pollinators.) Scroll down the page to the ‘Diversify bloom times’ illustration to see how bloom times are represented by bars that match the flower colours.
To fill in gaps in the table or to make substitutions, you can search the Prairie Moon Nursery’s online Seeds catalogue by sun exposure, soil moisture, bloom time, height, and bloom colour.