As the gardening season comes to a close in autumn, many warm-weather-loving plants begin to succumb to frost, effectively ending their growing season. Some plants are “frost-hardy” and will survive light frosts, when temperatures hover around freezing. Other plants that are slightly more frost-hardy will survive more severe freezes, when temperatures drop into the mid- to upper 20s. Edibles such as cabbage actually become better tasting when exposed to a few light frosts before you harvest them.
An extra-tall flowering perennial, Tatarian aster (Aster tataricus) begins flowering in September and continues into November. All asters are frost hardy, and Tatarian will survive winter well in zones 3 through 9. It produces masses of 1-inch, light lavender flowers on plants that grow 3 to 6 feet high. Despite its height, Tatarian aster does not need staking.
Grow it in full sun in a wide range of soil types. Tatarian aster quickly grows to form a large plant and is easily divided every three to four years.
A product of the University of Minnesota's chrysanthemum breeding project, the hardy mum "Sesquicentennial Sun," (Dendranthema x grandiflorium "Sesquicentennial Sun") is a golden-flowered, frost-tolerant mum that is reliably hardy through USDA zone 3 with winter protection. Garden mums begin blooming in late September and continue until killed by a hard freeze. Mums tolerate light frosts with temperatures falling into the mid-20s.
Plant garden mums in full sun in fertile, well-drained soil in mid-spring. Pinch the branch tips until late June to encourage the plant to branch out, which will cause it to produce more flowers. Cover it with hay or straw when it finally succumbs to frost in late autumn.
A member of the same family as edible cabbage, as well as broccoli, cauliflower and kale, flowering cabbage (Brassica oleracea) is grown primarily for its colorful fall foliage. Also called ornamental cabbage, the foliage turns shades of lavender, pink and cream after exposure to a few light frosts.
Plant flowering cabbage in late spring to early summer in full sun, in the same manner as edible cabbage. Keep the plants well watered and cultivate shallowly to remove competition from weeds. As other garden plants succumb to autumn frosts, the newest leaves on your ornamental cabbage will begin to change color, and the colors will become more intense with every frost. Include them in autumn indoor flower arrangements by cutting off the entire plant close to the ground.