While every month heralds some change in our gardens and landscapes, October brings transformation. Leaves and temperatures fall, animals may begin hibernation, migrating birds depart for warmer places or arrive here for the winter months, seeds disperse on wind and fur, and the first freeze is possible. Garden tasks include trimming along paths to make way for snow, seed harvesting, emptying hoses, and end-of-season weeding.
As usual, we leave most plant material standing for the winter. We harvest seed from some native species to add to restoration seed mixes sown after cold weather sets in. But many seeds are left in the garden, where birds and animals feed on them through the winter. Some fruits or seeds disperse to suitable places and experience winter’s cold moist conditions that break seed dormancy. Then they will germinate in spring. Seeds that don’t require cold moist conditions (referred to as stratification) won’t germinate in late fall, simply because it’s too cold. If they are not eaten during the winter, they will also germinate in the spring. The recommended time for overseeding is November to January, so October is ideal for collecting seed, determining species and seed quantities needed, and possible site preparation.
Early October usually marks the end of the blooming season. Showy goldenrod (Solidago speciosa), Riddell’s goldenrod (Solidago ridellii), and New England aster (Symphyotrichum novae-angliae) are often the last species in bloom, and the latest active pollinators visit them. All three of those plants spread only by seed (not by underground stems, or rhizomes); their numerous seeds may be the last to mature. In the warming climate, it is likely more species will extend bloom later into the fall.
This year, drought and rainfall patterns led to late season re-blooming in some species. After dry conditions in mid-summer, two substantial rains led to a second flowering phase in ox-eye (Heliopsis helianthoides), yellow coneflower (Ratibida pinnata), white prairie clover (Dalea candida), Joe-pye weed (Eutrochium maculatum), native field thistle (Cirsium discolor), and, to a lesser extent, spiderwort (Tradescantia ohiensis). Despite those rains, Dane County is still in severe drought at the end of this growing season.
Fall color can be affected by drought and temperature patterns. Subtle changes in leaf or plant color over the past two months give way now to chlorophyll loss, bright pigments, senescence, and drying plant tissue. Different species and even individuals of the same species vary in rates, color intensity, and timing (phenology) of color change. Prairie grasses provide dramatic color as their foliage and flower and seed heads change hues over a few weeks.
Few insects are active in the garden now. A few examples include woolly bear caterpillars, a late monarch and a common buckeye, and male common eastern bumble bees. Hidden from view are many dormant pupae, eggs, larvae, and even adult forms. Hollow stems and logs, as well as fallen leaves, may provide places for these dormant forms to overwinter.
The native plant garden is quiet – far too quiet – with the garden volunteers on break until spring. I deeply appreciate their dedication, support, great questions, and keen interest in native plants. Thank you, volunteers!
—Susan Carpenter, native plant garden curator