Jennifer Schultz Nelson
Extension Educator, Horticulture
There are several species of hibiscus that people typically grow in their landscapes, but some are native to tropical places and will not overwinter here unless brought indoors. Chinese hibiscus is one of these tropical types.
With a little extra care, it is possible to bring these plants indoors and have gorgeous flowers during the winter months. I have had one of my Chinese hibiscus plants for about 13 years now, and it is still going strong.
Historically, the tropical or Chinese hibiscus, Hibiscus rosa-sinensis, is believed to really be from China. There is some debate though as to whether early on it was developed by crossing two or more species of hibiscus also native to Asia. The other common name for Chinese hibiscus is "shoe flower"–in parts of India, the flowers have been used to shine shoes!
Tropical regions of the world use Chinese hibiscus much like we use shrubs in our landscape. Chinese hibiscus can only overwinter in Zones higher than 9 or 10 depending on the cultivar. The Extension publication I found from the University of Florida discusses Chinese hibiscus primarily as a landscape plant, with brief mention of new plantings' vulnerability in the "cold" northern half of the state. Unfortunately for us in Illinois, we are limited to containers unless we want to treat our Chinese hibiscus as an annual planting.
However you plant your Chinese hibiscus, the flowers are why you want to grow this plant. Although individual flowers only last a day in most cultivars, a typical plant in summer will be covered with more buds ready to burst into bloom. Flowers are five-petaled and have a long stigma poking out from the center surrounded by several stamens. Some cultivars have blooms only two inches in diameter, while others are up to twelve inches wide. Most cultivars when grown in good conditions will have flowers about four or five inches wide.
Flower color seems to be almost limitless, some solid colors, some patterns of several colors. The only flower colors not found in Chinese hibiscus are true black and true blue. Some cultivars are double-flowered, which means there is a second layer of petals, giving a very full, ruffled look to the flower. In order for a plant to produce a double flower some of the stamens, or male parts of the flower are directed to become flower petals very early on in development. The more "fully double" a flower is, the more stamens are sacrificed. In an extreme case there are no stamens left and the flower is sterile, so it produces no pollen at all. This control of flower development is genetic. The plant doesn't just wake up one morning and decide it will make double flowers today.
Chinese hibiscus need plenty of sun, but too much sun will likely produce smaller flowers and less of them. Sitting in the blazing sun all day in 90+ degree temperatures is too much for this plant. They do love direct sun, but need a break from it at some point in the day.
Not only is too much sun bad for the flowers, it's hard on the foliage too. This is especially true in Northern climates like ours where Chinese hibiscus spends the winter indoors. Unless you don't mind your plant frying to a crisp on its first day outdoors, you need to keep your plant in a shady spot and gradually expose it to more and more direct sun. It's a lot like people getting sunburned on the first nice weekend of the spring after spending the winter indoors.
Even if you do fry your plant to a crisp early on in the season, don't worry too much. In all likelihood the plant will drop the fried leaves and regrow new ones. This regrowth is part of how this plant has evolved to survive periodic dryness in tropical areas.
Yellowing and dropping leaves are symptoms of too much stress. Typical sources of this stress are overwatering, overfertilizing, and changes in light or temperature. As long as conditions are returned to favorable ones as soon as possible, the plant should recover. Dropping leaves is almost unavoidable when bringing plants in for winter. This drop is primarily due to less light available indoors.
To reduce leaf drop when bringing plants in for the winter, give the plant as much light as possible. Supplemental lighting is great, but not always possible. I have found as long as there is light available, the plant will adjust. They may look a little bare, but they will survive. Just wait out the sparseness until spring. Pruning or fertilizing during the winter will just encourage weak growth, unless you have a really good supplemental light source.
As a general rule, Chinese hibiscus are very thirsty plants. They take a lot of water, but do not like to have wet feet. A good potting mix for containers will provide both the moisture and good drainage the plant needs. During the hottest part of the summer, its not unusual for me to water my hibiscus every day. The winter however, is another story.
During the winter, unless you are adding a lot of good supplemental lighting, the whole plant slows down. This means the plant's water needs slow down too. Overwatering in winter will only promote root rot. I keep my plants on the dry side in winter, and they still manage to bloom periodically, with the best indoor bloom times in late September and late March. Miraculously they manage to bloom without supplemental lighting, just the light that comes through my southern-facing windows.
It takes a little practice, but it is easy to tell when your plant needs water, summer or winter. The Chinese hibiscus' leaves are normally shiny. When the plant needs water, before the leaves actually begin to wilt, they will look dull.
When spring finally comes, besides gradually exposing my plants to full sun, they also get a haircut. Any growth that happens indoors in winter tends to be spindly and generally sparse. I trim up to about a third of the plant away, and give a dose of fertilizer. I have had great results using fertilizers for blooming plants, which have more phosphorus relative to nitrogen and potassium (phosphorus is the middle number in the three numbers on a fertilizer label).
Without pruning, Chinese hibiscus can get very large. Like a lot of shrubs we grow in our landscape, Chinese hibiscus flowers best on new growth. Older branches become thick and the center of the plant will become bare with age.
Some people have asked me about hibiscus "trees" that are very popular patio plants. These are nothing but patient pruning of a Chinese hibiscus that was allowed to grow as a single stem to a particular height, then pruned to encourage branching. The technical name for this way of growing is a "standard". Other plants that you might see grown this way are roses, or fuchsias. Sometimes multiple stems are braided together. By removing all of the side branches except for the ones near the top, you have a "tree". These take a lot longer and require more labor to produce than the typical "shrub-like" hibiscus, so the cost is considerably more.
My mom took care of my oldest hibiscus while I was in grad school. When I finally bought a house, the hibiscus was in the first load of my "stuff" that my parents couldn't wait to get out of their house. Though I had kept up with its care early on, as grad school progressed and my time was limited, caring for the hibiscus fell off my priority list. I was shocked when I saw my hibiscus when my parents brought it to my house. It was huge. Not just big. Huge.
At that point it was about four and half feet tall and three feet wide in a twelve inch container. It was top heavy to say the least. In previous years I had tried to give my mom a pruning lesson, but she was afraid to try it, for fear she would kill the plant. My parents had strapped it into the back of their truck and it rode down here from Chicago, a little wind-whipped but alive. My husband took one look and asked where in the world we would put the thing.
I ended up violating every recommendation I've ever read about pruning and removed about two-thirds of the plant. The middle was bare, and the branches had gotten so thick that I needed to use my pruning saw! I also repotted it, nearly having to break the old pot to remove it. The roots were so overgrown you could hardly see any soil. I pruned away about two-thirds of the roots too, to balance out what I removed from the top. There were still plenty of roots to be had.It took a little longer than usual, but the plant regrew. It did not flower that first summer, but since has been covered in blooms. While you may think of tropical plants as fussy and delicate, I know first hand what a tough little plant the Chinese hibiscus is. If you've never grown one, try one this year and I bet you'll be hooked.