Defined as zones 6b and 7a on the U.S. Department of Agriculture Plant Hardiness Zone Map, Oklahoma can experience minimum temperatures of minus 5 degrees F in the northern part of the state. The state's biggest city, Oklahoma City, is in zone 7a, which nominally is warmer in the winter. Several cold-hardy tropical plants, including palm varieties, can survive in Oklahoma with proper care. Tropical plants used in colder climates are best suited for southern exposures and should be protected from wind by a fence or structure. In addition, adding an extra layer of mulch to the tropical plants before winter will protect roots.
Chinese Windmill Palm
The Chinese Windmill Palm (Trachycarpus fortunei) is among the most cold-hardy of palms and can flourish in southern Oklahoma, though it should be protected from wind, as the leaves may tear. This palm can grow to 40 feet and produces fan-shaped fronds, each on a flat, individual stem from a slender, central trunk. The Chinese Windmill Palm is native to southeastern China and Taiwan, and should be planted in full sun in Oklahoma. This plant needs regular water and dead or damaged leaves should be pruned.
Also known as the rose mallow or swamp mallow, the hardy hibiscus (Hibiscus moscheutos) is hardy in all of Oklahoma and produces the largest flowers of any hibiscus, up to 12 inches across. This plant can grow to 8 feet and blooms from late June until the first frost. The hardy hibiscus has jagged, oval foliage and blooms are available in pinks, reds and white. In Oklahoma, this hibiscus should be protected from wind and will die back in winter. It should be planted in full sun and requires regular water during growing season.
Technically a cycad, the sago palm (Cycas revoluta) is among the oldest plants on the planet and can survive winters in zone 7a (southern Oklahoma) with protection. These evergreen plants produce a rosette of large, spiky, fern-like fronds from a central base. Native to Japan, sago palms may grow to 10 feet, though they are very slow growers. Leaves are up to 3 feet long. In Oklahoma, sago palms may be planted in full to partial sun and require regular water. These plants should be amply mulched before winter and may be covered during particularly cold snaps, as frost damage may occur.