October in the garden can be warm and colorful or frosty and drab as leaves fall, dry, and blow into drifts and seeds disperse on wind, fur, and sweaters.

The month usually opens with good gardening weather. We finish planting as soil temperatures remain warm, dig cool season weeds, collect native seeds, deadhead flowers before seeds disperse (especially native “weedy” species that are not needed for Arboretum seed mixes), and place winter tree protection where needed.

Aside from trimming plants that have fallen across other plants or are covering paths, we leave native plant material untrimmed through the winter. This provides food sources and shelter for native birds and small mammals as well as over-wintering sites for insects.

During fall, the native plant garden literally holds seeds for next year’s growth. Seeds from species blooming late in the season can be collected and spread over existing gardens or in new areas – store seeds in paper bags in a cool dry place until planting time.  Seed spreading is best done later next month, when temperatures drop and the soil cools. The freeze-thaw cycle brings fresh seed into contact with small crevices in bare soil. Winter weather provides the cool, moist treatment that many forb seeds require to break dormancy.  Seeds harvested in the native plant garden are used in Arboretum restoration seed mixes developed by land care staff.

October also means migration for many species. Early in the month, we usually see the last monarchs of the year leaving for Mexico, where they spend the winter months in a specific montane habitat, on oyamel firs. These are the adults of the fourth generation of monarchs for the year. The migrating butterflies, in response to decreased daylight, fluctuating temperatures, and senescing milkweed, do not reproduce until next February when they will fly north and reach newly emerging milkweed in Texas or southern tier states. They will lay eggs there that grow into the second generation of butterflies that continue flying north. Those adults typically arrive in Wisconsin in May, when the milkweed is emerging.

This past season’s observations of monarchs included the egg stage (check the leaf undersides for one-millimeter-long oval eggs), larvae (five instars, the first tan with a black head, the others with white, black, and yellow stripes), compact green chrysalises, and adults (in their distinctive “floating” flight, mating, laying eggs, nectaring, and puddling).

For the gardener, it’s time to sum up, look ahead, and slow down. What worked well in your garden this season? What didn’t? Are there gaps to fill or changes to make for next season? Measuring areas, counting “spaces,” and recording your ideas for new additions will serve you well later when you propagate or purchase new plants. Mark future plant locations in the garden (using sturdy stakes labeled in pencil, which will not fade) or note places for new plants in sketches, maps, or photos.

As we end our 2025 native plant gardening volunteer sessions, I’m grateful to everyone who helped care for the garden this season. Thank you, volunteers! Your interest, dedication, and great questions are inspiring, and I deeply appreciate your contribution of time and ideas. This year’s data, summaries, and fall preparation will lead to more gardening and learning next year. In addition to caring for existing gardens in 2026, we look forward to planting the new garden that garden designer Darrel Morrison has drafted, which will extend from the large rain garden toward the dry prairie garden. Thank you, Darrel!

During the rest of the month, notice late-blooming natives like witch hazel (Hamamelis virginiana) or harebells (Campanula rotundifolia). Autumn leaf color variation is striking, as are branching patterns revealed after leaves fall. Even familiar plants and garden spaces look “new” as the light changes and you closely observe features that mark the end of one season and the promise of the next.

– Susan Carpenter, native plant garden curator