Let’s first address the confusion there seems to be within the genus Hibiscus. Over the years I have taken many phone calls regarding Hibiscus and my first task is to determine which species we are talking about.
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Hibiscus syriacus (Rose of Sharon) also known as Korean Rose is native to Asia and is the national flower of South Korea. It is hardy shrub from zones 4-9 and generally grows 6-8’ tall and shows off loads of flowers in the late summer. They have a wide tubular shape 2-3” across making them a favorite for pollinators. The flowers come in white, pink to burgundy, and blue for the most part, generally with a darker colored center. This shrub is easy to grow in most sunny locations and there are dwarf varieties available. The stems are thick and strong and may require thinning out through the years to promote a thicker more lush habit.
Photo credit: HBarrison on Visual Hunt/ CC BY-NC-SA
Hardy Hibiscus is perennial, meaning they die down in the winter and produce all new growth from the ground each season. They have huge, tropical blooms which bring an exotic feel to our climate. The stems are very thick ¾” and hollow, and they produce a very large clump 3-4’ across. The flowers are 6-8” across and in shades of red, pink, burgundy and white. These may also have a highlighted central color and again are favored by many pollinators. These are warm weather plants and quite often will not start to grow until June but once they begin they fill in quickly in both height and width.
Tropical Hibiscus is not hardy for our area however they thrive in the south growing year-round outside. Their blooms are generally in shades of orange, red and yellow and the size is slightly larger than the shrub Hibiscus syriacus. Once these are in bloom they will continue flowering right though the fall. You can purchase these each season for constant color on your patio or deck. With a little effort they can be wintered inside and brought outside again in the spring. Take care to use a systemic insecticide when bringing them indoors as they will become susceptible to mealy bugs and spider mites. They will thin out and drop yellowing leaves especially when first brought in. When taking them back outside for the spring it is a good idea to chop them way back and begin fertilizing to encourage all new growth which happens very quickly once the temperatures warm up. These are available as potted plants but also can be found in a tree form with braded trunks.