Fragrance is a bonus that pleases us humans and attracts large numbers of pollinators such as bees and butterflies. American painted lady butterflies use the foliage as a larval food plant, and other butterflies flit about sipping the nectar.
Right Plant, Right Place
Plant climbing aster in an area where the vines will be exposed to full sun for best bloom. Consider the fact that it is deciduous when deciding where to place it. Make sure that leafless mass of narrow, whippy stems will not detract during the winter.
In the wild, climbing aster can be found in freshwater marshes or other damp places, such as along the banks of rivers and streams. Although it can handle saturated soils, it adapts well to most landscape situations. A bit of extra watering during times of extended drought may be beneficial. Mulch the root area well to maintain moisture and moderate soil temperatures.
Heavy pruning may be necessary to keep the vines looking neat. If left unchecked, vines can grow from 12 to 20 feet tall. Pruning is best accomplished in late winter before new growth begins. Plants can be pruned back almost to the ground, if desired. Recovery is quick in the favorable weather of spring. Flowers form in fall on new growth, so severe pruning does not affect flowering. Plants cut repeatedly back to the ground will eventually form a self-supporting sub-shrub that can be attractive as a free-standing specimen or as part of a perennial or shrub border.
Left unpruned, the vines will grow in any sunny area. If no other plants are nearby, the lax stems will scramble along the ground and over themselves. Since the vines do not have holdfasts, tendrils, or other means of attaching to structures, they sprawl if no support is available. Stems are adept at weaving in and out of the branches of nearby trees, shrubs, and other plants. They also are easily trained to grow well on a sturdy trellis or fence.
Wherever climbing aster grows, volunteers are sure to crop up. The composite flowers produce many seeds that will sprout if they fall on favorable terrain. Gather the dried flowers and the shred them apart. Sprinkle the seeds on a moist seedbed to grow more for yourself or to share with other gardeners.
Climbing aster has had at least two name changes in recent years. Originally named Aster carolinianum, the Aster generic name fell by the wayside along with many other former members of the Aster genus when taxonomists discovered basic differences among most Eurasian and North American species. Now it is called Ampelaster carolinianum. Before this name change, it was called Symphyotrichum carolinianum, and some literature still refers to climbing aster by this name.
Almost all North American species of asters have been assigned to other genera. Only Aster alpinus, native in a wide range stretching from Asia and reaching across Alaska and down through the Rocky Mountains, remains in the Aster genus. Many former members of the genus have been placed in the Symphyotrichum genus, including the New England aster, the smooth aster, and others. More thorough explanations for these name changes can be found on the web.
Regardless of which name you assign to the climbing aster, you will find that it will add color to the garden in late fall when so many other plants have given up the ghost and hunkered down for winter. Try it out if you live in USDA Zones 7-9, or even stretch the limits a bit if you have microclimates that are favorable.