This month’s Ask An Expert Question Is: I would like to grow a butterfly garden but it’s difficult to find milkweed plants. Can you recommend any other plants that would attract butterflies?
Milkweed plants are in high demand right now and so may be tricky to find at certain times of year. St. Williams Nursery & Ecology Centre carries five different species of Milkweed (Common/Kansas, Butterfly, Swamp, Whorled, Sullivant’s), and each of them attracts butterflies as well as bees, and all host Monarch butterfly caterpillars.
Milkweeds are great for feeding monarch caterpillars, but adult monarchs, and other species of adult butterflies feed a variety of native summer wildflowers.
Remember, if a plant has a colorful flower, it needs to be pollinated by an insect of some form or another. The truth is– all wildflowers are “pollinator plants”, particularly the native ones.
Not all flowers are created equally though. Some have evolved to attract bees, some to attract humming birds, and some are specialized to attract butterflies. However, the vast majority of flowering plants are pollinator generalists, meaning the can be pollinated by a wide variety of animal mutualists.
Butterflies usually prefer flat landing pads from which to feed. The flat topped inflorescences of aster and goldenrod plants are ideal landing pads, and the short, simple flowers are easy for butterflies to access. Many plants in the Aster family have these features, and are a safe best for attracting butterflies and other pollinators.
Few people realize that goldenrods are native plants and that there are at least a dozen species that make ideal garden plants. Not all are aggressive spreaders like Canada Goldenrod. A complete list of the best goldenrods for the home garden is included at the end. Also, please note that goldenrod does not cause allergies. In fact, no plant with large colour can cause allergies. Since they are insect pollinated, their pollen grains are too heavy and sticky to be carried in the wind and into your nose. All of your pollen allergies are caused by wind-pollinated plants. Most people who think they are allergic to goldenrod are actually allergic to ragweed, whose small green flowers are wind pollinated. Goldenrod gets blamed because it’s so showy and ubiquitous.
Some large butterflies are drawn to reds and oranges over other colours, but there are no hard and fast rules for colour. Flower form appears to play a larger role. For example, plants with bilaterally symmetrical (like a face) and tubular flowers are adapted to attract bees (eg. Beardtongues, Blue Lobelia). Butterflies can’t crawl inside these tubes to access nectar. However, butterflies do have long tongues to access nectar hidden away in long skinny nectar spurs, so long as there are a landing pad for them to hold onto. A wonderful example of pollinator by butterflies driving the evolution of flower form and colour can be seen in Cardinal flower, Lobelia cardinalis. It’s closest relatives have stout blueish flowers, specialized for bees to pry open and climb inside. Cardinal flower on the other hand had red petals, and narrowed, elongated flowers that restrict bees from entering, allowing only butterflies with long tongues and hummingbirds to reach the nectar inside. The bottom lobe of petals has even widened to allow butterflies to land.
While monarchs rely on milkweed for their young to eat, other rare and threatened butterflies rely on other specific food hosts for their offspring. Mottled Dusky Wing caterpillars feed primarily from New Jersey Tea, and Karner Blue Butterfly caterpillars eat only on Blue Lupine.
To help your garden appeal to butterflies all year round try these native species as nectaring hosts and larval hosts: