Why Native Plants Matter
by Mohan Iyer, Mississauga Master Gardener
All photos ©2020 Peeter Poldre
We all grow a variety of plants in our gardens and when well planned there will be plants in bloom throughout the spring, summer and fall. Have you ever wondered why there are more bees and insects on some flowering plants as compared to others or why the row of Eastern White Cedars has so many more insects than the non-native yew or burning bush?
The answer is quite simple. Plants and insects have co-evolved over millions of years. In fact, beetles were pollinators even before bees evolved. Insects are the most common pollinators for our vegetables, fruits and flowers. Many plants have finished flowering by late summer, but bees, butterflies, moths, wasps, and hoverflies are still on the wing foraging for food. The arrival of fall brings late-flowering plants. Blooming late in order to supply pollinators with food right up to last call in fall, the super-food nectar they produce helps insects build up energy needed for winter hibernation. Late-bloomers also have seed heads that provide birds with a source of winter food.
Above: This bumblebee is enjoying the abundant pollen produced by a late fall- blooming bluestem goldenrod.
Well, where is this all leading us? Native plants have adapted well to our weather and they have specific flowering and fruiting periods. Insects have evolved accordingly and a very good example of this evolution is that of the monarch butterfly. This butterfly’s life cycle is intricately linked with the life cycle of the common milkweed to the extent that absence of the plant will cause the extinction of the butterfly.
Above: The monarch caterpillar feeds exclusively on milkweed species.
Similarly, other native plants are hosts to and support a great number of insect and bird species as the seasons progress. For example, from late summer to fall, species of aster and golden rod are hosts to different types of insects. These insects then attract several species of resident and migratory birds that feed on them. Many migratory species of bird rely on the availability of insects and fruits in their migration path and have chosen these routes based on the availability of such resources. Many varieties of native grass also provide shelter and food for different species of insects and birds. Birds like Dark- eyed Junco, Redpolls and American Goldfinch feed on the seeds of aster and other grasses through fall and winter. Seeds from pine, spruce, hemlock, hickory oak and cherry trees all provide food for the Downy, Hairy and Red bellied Woodpecker and for the American Goldfinch in winter.
The American Robin and some late migrating thrushes will feed on the berries of the staghorn sumac in winter. The Black-capped Chickadee also feeds on fruits and berries that are available throughout the fall and winter months.
Above: A native staghorn sumac seed head can nourish this ruby-crowned kinglet during the fall and winter months.
Plants provide shelter to overwintering insects through the cold and harsh winter months. In fact, several insects will begin to take shelter in leaf litter, tree bark and rotting wood in late summer, long before the temperature plummets to freezing. The dead plant material of our native plants also helps with the overwintering of various insect species. An un-manicured garden, especially around hedge and shrub bases, provides much needed overwintering sites. Plants with pithy stems such as elderberry, raspberry, sumac and other perennial and annual flowers provide great nesting sites for bees.
Above: Hollow and pithy stems are favorite shelters for overwintering cavity-nesting bees.
Restoring native plant habitat is vital to preserving biodiversity throughout the year. By creating a native plant garden, each patch of habitat becomes part of a collective effort to nurture and sustain the living landscape for birds and other animals.
Mississauga Master Gardeners