October’s shorter days usually bring some warm sun along with cool autumn rains and light frost. The latest flowering herbaceous plants—showy goldenrod (Solidago speciosa), New England aster (Symphyotrichum novae-anglia), frost aster (Symphyotrichum pilosum), and harebell (Campanula rotundifolia)—finish blooming before mid-month. Fall color changes continue and leaves drop from woody plants. Seeds from warm season grasses and forbs mature and disperse via animals or the wind. Garden tasks include collecting seeds, trimming along paths and trails, and noting which plants to order or propagate for next spring.
Volunteer sessions usually end this month—with many thanks to our gardeners for their dedication and contributions throughout the growing season. Planning for next year begins with data entry and reports about the garden, monitoring projects, and volunteer hours. Garden outreach questions and events continue year-round; soon we begin plans for the Native Gardening Conference on September 20, 2020.
In September, I attended the annual Cleveland Pollinator and Native Plant Symposium and presented about managing native plant gardens. The keynote talk, by Larry Weaner, described gardens and larger landscape designs inspired and guided by ecological principles. Co-authored with Thomas Christopher, his book Garden Revolution: How Our Landscapes Can Be a Source of Environmental Change provides background and illustrations of these ideas and designs.
Another speaker, Przemek Walczak, related his experiences dealing with erosion and degraded land while restoring a native eastern woodland garden at Chanticleer, a public garden near Philadelphia. Scott Hoffman Black of the Xerces Society responded to a recent article about insect populations with his own article, coauthored with two colleagues, “Declines in Insect Abundance and Diversity: We Know Enough to Act Now.” Sam Droege, a bee expert based in Maryland, shared habitat recommendations and remarkable high resolution photos of bee specimens from the USGS Bee Inventory Monitoring Lab. These images are entirely in the public domain.
Native bee diversity in North America includes 4,000 species (500 Wisconsin species). We were able to view Droege’s bee collection (donated to the Cleveland Museum of Natural History), including a specimen of Bombus bohemicus, a parasitic bumble bee that invades nests. This bee has not been found in the field for many years because its two host species, rusty-patched and yellow-banded bumble bees, are quite rare. I also attended a fascinating and informative session on woodland plant propagation—all of the species described from northeast Ohio are present in our southern Wisconsin flora.
At the Arboretum, visitors’ questions lead to research that reveals interesting stories. A recent question (with photo) about a large “green flower” turned out to be the bunch gall or rosette gall of Canada goldenrod (Solidago canadensis). The terminal bud is affected by a small insect—a Cecidomyiid midge Rhopalomyia solidaginis—laying eggs there earlier in the season. The top of the plant responds by forming a compressed flower-like leaf structure. According to BugGuide, this gall maker is considered an inquiline, or ecosystem engineer, a species that creates habitats for other species by providing food or shelter to them. The BugGuide website includes further information about other galls found on goldenrod stems and leaves, still visible during the fall months.
—Susan Carpenter, native plant gardener