Tree Talk: Blossoms and butterflies

Summer is winding down and it's time to take notice of the things that represent Nature's summer-best before they're gone for the season. Right outside my office window is a display of purple coneflowers, now in full bloom. It's a magnet for countless types of marvelous creatures, including bees and butterflies and even an occasional hummingbird. One of the showiest visitors over the past few weeks is the Canadian tiger swallowtail, a large native yellow and black butterfly with tails on each hindwing. Females have a blue band or row of spots on the hindwings, differentiating them from the males. Some people have an aversion to insects, but how can you not admire a butterfly?

Butterflies have a complete life cycle, or metamorphosis, with four distinct life stages: egg, larva, pupa and adult. The cycle is different and specific for every different type of butterfly. The host plants for most North Dakota butterflies are herbaceous. The most familiar butterfly, the monarch, needs milkweed plant as larval food to complete its life cycle. For the tiger swallowtail, eggs are laid on leaves of woody host plants including ash, poplar, willow, birch and wild cherry (the hidden "tree connection" for this week). Eggs hatch into larvae, which molt through five instars or growing stages, feeding voraciously on the leaves of the host plant. Swallowtails are not pest insects, so don't worry that the larval stage will inflict serious harm on any trees that happen to donate a few leaves in this process. With insect species, the larger the adult, the larger the full-grown larva – which can be a startling discovery in the garden. Swallowtail larva possess a red or orange forked structure on the back of the head which is displayed like a snake's tongue and releases a foul-smelling odor when the caterpillar is disturbed by a predator. Disgusting? Perhaps. Cleverly effective? Absolutely. Finally, the larva forms its overwintering resting stage, a chrysalis, tucked inside the shelter of curled leaves. Adults emerge the following year, in early summer. And the cycle repeats.

Butterflies have one goal: to survive long enough to perpetuate the species. While caterpillars obliviously chew their way to pupation, butterflies cannot "eat." A butterfly mouth consists of a coiled proboscis which extends like a drinking straw, from which they drink water and nectar. Sugars in floral nectar are the perfect diet to sustain adults to find a mate and develop and lay eggs on a preferred host.

To attract butterflies to your piece of the world, provide a sunny location with a variety of plants that have overlapping bloom-times throughout the summer. Native plants are good because these plants have co-existed with native butterflies and usually, Mother Nature does things right. Black-eyed Susan, purple coneflower, sunflower and goldenrod are native species that are tough and will provide a visual display in mid-summer through fall. Avoid using insecticides because chemicals don't discriminate well; they are equal-opportunity buzz killers. Keep in mind that while you may be attracting butterflies, the larval host plant should also be nearby for egg deposition. But don't worry – butterflies have already figured out what to do.

For more information see NDSU Extension publication E1266 (2019), "Butterfly Gardening in North Dakota". Enjoy!