Located in Eastern Tennessee, Knoxville is in the U.S. Department of Agriculture (USDA) Plant Hardiness zone 6, though temperatures tend to be a little warmer in the city center than in the suburbs. Temperatures in zone 6 can reach a low of minus 10 degrees F in the winter, but summers are warm. There are many attractive plants that can thrive in pots during a Knoxville winter.
Blue Oat Grass
Blue oat grass (Helictotrichon sempervirens) is an evergreen perennial that is hardy in zones 4 to 9 and will thrive as a potted plant in Knoxville. Blue oat grass is a fountain grass with narrow blue-gray leaves that gracefully droop. It produces small cream-colored blooms in late spring to early summer. This grass may be planted in containers and requires full sun and good drainage. Blue oat grass is invasive and will spread if planted in the ground. In containers, it should be divided periodically. While blue oat grass will thrive in winter in Knoxville, it may turn brown or gray at the height of summer in some areas.
Hibiscus is divided into two distinct categories: tropical and hardy. Tropical hibiscus (H. rosa-sinensis) has glossy green leaves, and blooms are usually orange, peach, salmon or yellow. Tropical hibiscus can survive winter in pots in Knoxville with proper attention. Since these plants are usually hardy in zones 9 to 11, they should be sheltered in winter, and may be planted on a sun porch or protected area to avoid damage. The payoff is a tropical-looking plant in the dead of winter.
Hardy hibiscus (H. moscheutos) is also known as rose mallow or perennial hibiscus and is hardy in zones 5 to 10. This variety will not just survive winter in a pot in Knoxville, but should flourish. Many of these hibiscus are hybrids, and they are available in pinks, reds and whites.
English lavender (Lavandula angustifolia) is traditionally hardy in zones 5 to 9 and will do well over the winter in pots in Knoxville. Lavender, which has gray-green leaves and purple or white flower spikes, will help to add some color to a winter landscape. This plant grows to about 4 feet and requires full sun and moderate water. English lavender should be trimmed right after summer bloom to keep the plant neat. Another alternative is French lavender (L. denata), which is more tropical and would require some winter protection in Knoxville. The advantage is that if planted on a sun porch, or if the winter is mild, it may bloom into winter. French lavender is traditionally a tropical and is hardy in the ground in zones 9 to 11.