Hibiscuses are often grown from seed. They are fast growers, which means that even if the hibiscus seeds are not rated to your United States Department of Agriculture (USDA) zone, they can be grown as annuals and enjoyed the first and only year. In addition, seeds not rated to your zone can be grown as perennials if they are planted in pots and brought indoors before the first frost. Hibiscus seeds are available in many varieties--with just a few listed below--but in general, plant them after the last frost, or indoors 6 weeks sooner to be transplanted later.
Scarlet Swamp Hibiscus
The scarlet swamp hibiscus (Hibiscus coccineus)--also known as the Texas star--grows to be 7 feet tall and has red blooms that are 6 to 8 inches wide. Each fall the plant will die back and grow again in the spring. The scarlet swamp hibiscus is winter hardy in USDA zones 7 to 11.
The Chinese hibiscus (Hibiscus rosa-sinensis) seeds are available in just about every bloom color except for blue, although the most common have red blooms. The Chinese hibiscus is not cold resistant at all and needs to be brought indoors when nighttime temperatures drop below 50 degrees Fahrenheit. For this reason, hibiscuses of this variety are often grown in containers in USDA zones colder than zone 8 and below.
Rose Mallow Hibiscus
The rose mallow hibiscus (Hibiscus moscheutos) is a good hibiscus choice for marshy areas and wet soil conditions, although it prefers soil that drains water well. Many cultivators have been bred from this hibiscus variety including Lady Baltimore, Lord Baltimore, kopper king, moy grande and disco belle, just to name a few. Each cultivator is rated to different USDA zones, but in general, they can tolerate much colder climates than other perennial hibiscuses, usually to zone 5.
Confederate Rose Hibiscus
The confederate rose hibiscus (Hibiscus mutabilis) is one of the largest hibiscuses, able to reach a height of 15 feet near coastal regions. The confederate rose is available in many seed varieties, including those that will grow to bloom red, pink and even double white flowers. Hardiness varies among the different kinds of confederate roses, but usually they are winter hardy in USDA zones 8 to 10.
Red Leaf Hibiscus
The red leaf hibiscus (Hibiscus acetosella) is grown for its foliage as well as its blooms. While only hardy to zone 8, the best known cultivator is the red shield, which has purplish-red leaves that resemble Japanese maples.