A full ten months of bloom is not an exaggeration dreamed up to sell
more plants. To a large degree it is a "depends upon where you garden"
circumstance. If you garden far north of me and have three months of mostly
snow cover it would do you little good to have plants in flower come
December. They would be under snow and out of sight. Further south of me
can do better than ten months of bloom much easier than in my garden.
Here in Southern Indiana we are not so far south as to sit under palm trees along the Ohio River. However, it is not all that difficult to have eleven months of bloom in my garden with perennials. Add trees and shrubs to the list and one can have the full 12 months of bloom. Witch-hazel can reliably bloom from December through April, and often does in my garden. Perhaps not as many, showy perennials as in May, but certainly welcome when all else is some shade of brown under a gloomy winter sky.
The mid-west has been provided with relatively few evergreen natives
so that is a clue to gardeners that winters can get pretty rough. I
consider green to be a color, especially a color to be appreciated during
winter months. Give thought to perennials that are green throughout the
winter months providing color in their own right and background for other
perennials that choose to bloom in the cold months. Perennials as Arum
italicum, the Black Calla, evergreen ferns and helleborus deserve
consideration for winter color. You can have a hellebore in bloom in your
garden from December through May by picking species and hybrids by bloom
time.
Spring and early summer are no-brainers for that is the time most of
us garden. There is certainly no shortage of plant material that blooms in
the shade from April through mid-July.
From mid to late July and into November most gardeners have given up. "Too hot, too dry, nothing in bloom in the shade garden" are words I often hear. Color in the garden during this time of the year is just a matter of becoming aware. A few perennials that come to mind are monkshood (Aconitum), the fall-blooming Japanese anemone and our native Delphinium exaltatum (Tall Larkspur). Watch for bloom times given with plant descriptions in this catalog. When planning and purchasing a perennial that blooms in spring consider ordering a plant that blooms in the fall. If ordering a summer bloomer, consider a winter blooming plant, adding balance for the complete year.
In February I will go into more detail about the winter garden, listing my favorite perennials, shrubs and trees that provide color reliably in my garden.