Some months hold more seasonal change than others. In October, the first frost may arrive, daylength and temperatures decline, fall color develops fully, and winter dormancy begins for some plants and animals, marking the autumn transition. Garden tasks include harvesting seed, trimming along paths and trails, installing winter signage, weeding, planning areas where plants will be added next spring, and winterizing hoses and other equipment.
Flowering in our native plant garden usually ends in October, when the last small heads of showy goldenrod (Solidago speciosa), New England aster (Symphyotrichum novae anglia), and Riddell’s goldenrod (Solidago riddelli) bloom. Witchhazel (Hamamelis virginiana), a shrub or small tree, blooms in October and November with small, strap-like flowers that give rise to clusters of fruits that persist on the twigs throughout the winter. As floral resources become scarce, some pollinators that do not migrate (for example, current year bumble bee workers and males, and adult solitary bees and wasps) die. Others go into dormancy. Bumble bees are overwintering, one by one, as mated future queens. Solitary bees and wasps are either underground or in hollow stems or crevices, each egg or larva provisioned with a suitable food source: pollen or insects, respectively. Butterfly species survive winter at different life stages, some migrating, others in dormancy.
Throughout the month, plant seeds disperse: by wind (for example, many species in the sunflower and grass families); in fruits that birds or other animals spread (for example, walnut); by being “flung” from the plant (for example, jewelweed and flowering spurge); or simply by falling (for example, relatively large seeds like Silphium). Seeds that reach soil late in the season – and are not eaten over the winter – will germinate when conditions warm in the spring. Seeds that require a treatment of cold moist conditions will germinate after winter breaks their dormancy and warmer conditions arrive.
Fallen leaves provide cover for dormant invertebrates, are eaten and decomposed by detritivores and microorganisms, and return nutrients to the soil. Dried plant material holds seeds and overwintering invertebrates and also provides cover for wildlife. Gardeners can support this part of the natural cycle by not trimming back plants in the fall and leaving fallen leaves in the garden. Leaves removed from turf areas can be piled or used as mulch on beds or under trees. In the spring, those leaves can be moved to allow more sunlight to reach emerging plants, and dried plants can be trimmed or raked off the beds before new growth comes up. Overwintering insects will emerge from the material as temperatures rise into the 50s next year.
As autumn settles into your garden full of life, note that dormancy in the quiet months is a key link in your garden care and land stewardship.
—Susan Carpenter, native plant garden curator