Ẃ́áżupi Wi, the Dakota word for final harvest moon, reminds us that the crisp blue rays of the autumn sky point toward shorter winter days ahead. A small reminder of the change of season at the Arboretum is the appearance of an Isabella tiger moth caterpillar, with 13 segments covered in black and reddish, non-stinging, bristle tufts called setae.
As plants die back, caterpillars drop off to seek winter shelter in the leaf litter. They produce a cryoprotectant to protect parts of their cells from freezing and preserve the body to thaw out in spring.
Can the woolly bear, willy worm or fuzzy wuzzy predict winter weather?
It’s time to gather every bit of summer’s bounty while we enjoy the colors of the Arboretum’s gardens. The many prairie sites on the Arboretum grounds, including Spring Peeper Meadow, the Bennett-Johnson Prairie and Lake Tamarack, are a buzz of pollinator activity during the final harvest of the year.
Hang on to your aster, it’s going to be another bad hair day.
A hairy falseaster cradles a common eastern bumblebee as pairs of tarsal claws on the end of its feet help the bumblebee hold on, pack pollen and groom. These bumblebees show slight variations in size and color intensity, but one consistent feature is an errant tuft of hair (setae) that sticks out over the head like a cowlick.
The bumblebee’s tarsal claws attach to the rays of a hairy falseaster. Even though it is called falseaster, it really is in the Asteraceae family. It shares the family trait of a composite flower head with a receptacle base surrounded by involucre bracts containing ray and disk florets. It’s a big family with more than 1,600 genera and 25,000 species. The Arboretum is filled with members of the Asteraceae family, including cosmos, artichoke, leaf lettuce, sunflower, liatris, marigolds, dandelion and zinnia, to name a few.
(Left) Purple rays, a green bee and gold flowers paint Mardi Gras colors in the prairie. (Right) The flipside of this aster reveals some of the Asteraceae family traits.
The bright blue rays of a New England aster attract a green metallic sweat bee (this one is not attracted to the salt in your sweat). The shape of the tiny yellow true flower is attractive to many bees and pollinators. The small flowers bloom in succession from the outside to the inside of the center disc and invite pollinators to return day after day.
The Asteraceae family evolved in present-day Argentina 50 million years ago. Another member of the family, dahlias, are native to South and Central America. The Dahlia Trial Garden along Three-Mile Drive is a display of fall color. The brightly colored dahlia rays, around a disc center, have morphed into different flower head shapes described as single, peony, anemone, waterlily, cactus and pompom. Dahlias are frost-sensitive but are at their best in autumn. The pompom dahlia is bred for the natural involute curl of the ray.
The rays of a dahlia unfurl in a Fibonacci sequence.
On the other hand, lichens have a complicated family tree. They are complex organisms composed, at the very least, of a fungal component and an alga/cyanobacterial component, but are classified under their fungal component. On an old wild plum tree at the Arboretum, a fruticose lichen is growing. The plum tree can be found on the Arboretum’s Lichen Trail. Visitors can use this Google Earth map to discover the hidden locations of lichen varieties across the Arboretum.
To learn more about lichens, sign up for my upcoming Lichen Scouting class at the Arboretum. The class, on Nov. 1 at the Farm at the Arb, provides attendees with an introduction to lichens as well as a tour of the best lichen scouting sites at the Arboretum. I hope to see you there!
Golden-eye lichen at home on a wild plum tree in the Arboretum.
Zan Tomko is an artist, horticulturist, Minnesota Master Naturalist Instructor and a co-founder of the iNaturalist Minnesota Lichen Map Project. To learn more about the University of Minnesota Extension’s Master Naturalist program, visit their website.