Like my yard, most urban yards have some areas of shade and part shade from nearby trees and buildings. I still plant for pollinators in these areas with less sun.
North, South, West, East
Observe your yard to figure out which direction you’re facing (North, South, West, East) and where shade is cast by trees and buildings. Also, keep in mind that this will change whenever neighbours build taller houses and cut down trees.
Open areas facing south will get the most sun. Also, large trees with high crowns (without branches on the lower part of their trunk) still let a fair bit of light reach beneath them on the South side.
Assess your light conditions at different times in spring or summer. In spring, leaves may not be out yet, or they may not be full-size. By fall, the sun is lower in the sky and casts longer shadows, making your yard seem a lot shadier that it really is earlier in the growing season. I have planted things in the fall thinking that they were in the shade, only to find them baking in the sun the following summer.
When you plant a tree and want it to create shade, plant it on the South side of your yard. If you want to maximize your sunshine, plant it on the North side.
How much shade?
The light requirements for plants are described as
- Sun: 6 or more hours of sun
- Part shade/light shade/part sun: 3 – 6 hours of sun, preferably with sun in the morning. For simplicity, I lump all of these together.
- Shade: less than 3 hours of sun, preferably with sun in the morning or filtering through leaves. Few plants can grow in dense shade with no sun at all.
To determine how much sun your garden location receives, check it throughout the day, every hour or two to track the hours of sunlight.
Since Ottawa is at a northern latitude, our summer days are long and the sun is intense. I find that some non-native plants that supposedly want full sun wilt and fade. For example, my peony blossoms look awful in mid-day sun, so I moved them to a part shade location.
Give it a try
If you end up placing a plant in a spot that is too sunny or too shady, it’s not a catastrophe. You can move the plant if it is really struggling. You may be surprised that your plant does just fine outside of its preferred conditions.
Often, plant tags and seed packets recommend ideal conditions, which I don’t always have in my yard. I have very little full sun, but I grow many full sun plants in part-shade. Even if a plant prefers a lot of sun, it may be okay with less sun. It may not bloom as much, or it may be a bit taller and require staking. Since I grow multiples of many plants from seed, I can place them in different locations around the yard to try out a range of conditions.
Focus on spring and fall flowers in part shade
I focus spring and fall plantings in shady parts of the garden. Spring-blooming woodland plants take advantage of the sun that’s available before leaves unfurl above them. Understory trees and shrubs also grow in shadier areas and bloom in the spring. These flowers are critical food for early-emerging solitary bees and bumblebee queens.
For fall, there are varieties of goldenrods and asters that grow in part shade. I then place the summer flowers in the area of the garden with more sun.
The Nature Web has an interesting 3-part article “A Butterfly Garden that Embraces the Shade”. The trees that make the shade are actually beneficial to pollinators too; native trees are host plants for hundreds of kinds of butterflies and moths. Violets and Golden Alexanders, which grow in woodland clearings, are also host plants for butterflies. Spring flowers on some trees provide nectar and pollen, such as Red Maple, crabapples, Serviceberry, Pagoda Dogwood, and Redbud. Fallen leaves provides winter protection for butterflies. There is even a kind of milkweed native to southwestern Ontario, called Poke Milkweed, that grows in shade.
The Corner Pollinator Garden and Wildlife Habitat 