By early August, the summer solstice in June is more distant than the approaching autumnal equinox in September. Spring and early summer’s vigorous garden growth shifts to late season flowering and especially fruit and seed development. Garden hues change subtly from green to yellow-green, tan, and light brown. Garden tasks include weeding, planting, edging, trimming paths and trails, monitoring bees, and recording plant species lists. We harvest seeds from more plant species as late summer blooms fade and seeds mature.

Interesting life cycle stages and life histories are a hallmark of August changes in the garden. American goldfinches nest in mid-summer, when thistle down (fibers that disperse seeds on the wind) becomes available for nest construction. A small amount of dried grass or tiny roots help hold the soft woven nest lining. Thistle seeds are an important food source. Unlike other birds, goldfinches feed seeds (instead of insects) to their young. During August, we’ve observed them extracting mature seeds from ox-eye (Heliopsis helianthoides) and bee balm (Monarda fistulosa) heads in the mesic prairie garden.

Barn swallows nesting in mud nests under the Visitor Center eaves, on wall ledges, and on our entrance door hinges are reaching the end of their nesting season. They feed on insects caught in swooping flights. The youngest fledglings progress rapidly from tentative wing flaps to strong flying. We’ve noticed them congregating along the upper edge of the solar panels on the Visitor Center. Soon groups will fly out over the Curtis Prairie. By the end of the month, the swallows begin to migrate to Central and South America.

Wild turkey hens are traveling around the garden (and the Arboretum) with their poults. As the poults leave the ground nest shortly after hatching, it’s common to see two or more hens form large groups with their young. We’ve observed hens with sixteen or more poults of different sizes from different broods. In the garden we notice them feeding on fruits, seeds, acorns, nuts, and insects.

We see noticeably more bumble bee gynes (future queens) in August, often foraging on native field thistle (Cirsium discolor) and giant hyssops (Agastache spp.). The presence of male bumble bees and large newly emerged “future queens” signal the reproductive phase of the bumble bee annual life cycle. Some species, such as the two-spotted bumble bee, have likely completed the 2026 season and the (mated) gynes are already “overwintering” individually in their hibernation chambers. Late season bumble bees and other pollinators will finish their flight seasons nectaring on a diversity of asters and goldenrods coming into bloom this month. Flat-topped aster (Doellingeria umbellata) and elm-leaved goldenrod (Solidago ulmifolia) are the first aster and goldenrod to flower in the shaded bur oak savanna garden.

August is also a good time to search for the tiny wind-pollinated flowers on warm season native grasses and anticipate collecting their seeds next month along with many other species.

– Susan Carpenter, native plant garden curator