By Lois Scott, Master Gardener
Life has been busy in my garden lately, and I don’t necessarily mean me! My husband Ray and I have been enjoying the array of pollinators that are busy in the garden. What has us particularly excited is seeing species of butterflies that we have not noticed in the garden before. For example, Ray identified a Large Wood Nymph butterfly (Cercyonis pegala) that I noticed feeding on heliotrope. Although it spent a lot of time feeding on the heliotrope this is not a host plant for this particular butterfly. According to The Audubon Society Field Guide to North American Butterflies host plants for the Large Wood Nymph are native grasses such as Little Bluestem (Schizachyrium scoparium).
So, what exactly is a host plant and why is it important? Host plants are plants that an organism, (larva) lives on and lives off of. A well-known example is the Monarch butterfly. It will feed on a number of nectar plants including milkweed but Monarch larvae only feed on milkweed (Asclepias) species. Milkweeds are the Monarch’s only host plant. Important pollinators like butterflies and moths need host plants on which to lay their eggs and enable the subsequent larvae to have a food source. The photo below shows Little Bluestem (Schizachyrium scoparium) in the foreground is a host plant while the Mexican Sunflower (Tithonia rotundifolia) behind it is a nectar plant.
According to the Ottawa Field-Naturalists’ Club (OFNC) butterflies need plants that are good sources of nectar, sun, shelter from the wind, and host plants on which to lay their eggs. Yes, larvae eat the leaves on the host plant but typically do not cause serious damage. Along with providing a list of plants for nectar sources this site gives a list of host plants for larvae for specific butterflies. Many of the host plants are trees including birches, willows, dogwoods, oaks, hops, cherries and hackberries to name just a few. Other host plants include native wildflowers and grasses.
The OFNC site provides more details on providing the most desirable conditions for butterflies and makes the point that to restore butterfly populations we need to recreate suitable habitats for them. This is another list of valuable host plants.
If you are interested in attracting more butterflies consider adding some of these valuable host plants to your garden. Many of these plants can be sourced at Peterborough’s Ecology Park where you can also get expert advice on suitable plants for your garden conditions.