Tropical hibiscus plants remind us of the sun and beauty of paradise because they are found growing wild in Hawaii, Mexico, the Bahamas, and many other tropical regions. Keeping this in mind will help understand the care requirements needed for growing hibiscus in the harsh Midwest climate. The tropical hibiscus plant is NOT hardy and will not survive our Midwestern winter temperatures outside. However, the plant can be brought inside and grown in a sunny window for the winter months. It may even flower! As soon as danger of frost is past in the spring, the hibiscus can be placed outside on a deck or patio to enjoy its beauty all summer. In the fall when night temperatures begin to drop, bring the hibiscus back inside again for enjoyment all winter.
Water and Fertilizer
OUTDOOR CARE: The leaves of the hibiscus are very broad and are not protected by a waxy cuticle layer. Therefore, they lose tremendous amounts of moisture to the air through evaporation and transpiration especially on hot, windy days when exposed to full sun. It is imperative to water these plants at least once a day during these conditions. Saturate the soil until water flows freely out of the drainage holes underneath the pot. Be sure to remove any excess water that is not reabsorbed by the plant from the saucer within 10-15 minutes.
During periods of frequent watering, it is important to replenish the nutrients to the soil. Do this by using any general purpose water soluble plant food mixed with water and applied to the soil surface. The general rule of thumb is to apply fertilizer after every fourth watering.
*Note: It is important to over water the hibiscus plant as long as the pot it is planted in has free flowing drainage holes. However, pots that sit in saucers full of water for long periods of time may develop root problems that can damage or kill the plant.
INDOOR CARE: In the winter months when the plant is inside, reduce the frequency of watering. The light levels in a house are much less than outside; there is no wind to dry out the leaves; and the days are very short, usually gray and dark. Therefore it will take the plant longer to dry out than it did during the summer months outside.
Water the plant only when the soil surface appears very dry and the leaves of the plant barely begin to wilt. Follow the same general rule for fertilizing: after every fourth watering, about once a month or so in the winter.
*Note: Excessive wilting of the leaves will result in yellowing and eventual leaf drop. Do not worry! The plant is not dead. It will recover and send out a whole new set of leaves and flowers. Simply water the plant thoroughly and follow the pruning advice in the next section.
OUTDOOR CARE: The hibiscus may drop all of its leaves and look terrible, but with proper pruning and care, it’ll bounce back and be blooming beautifully in a few weeks.
In the summer, should the leaves yellow and fall, use pruners to snip off the tips of each of the branches, removing the last 3-4 leaves on the stem. Those will probably be the only leaves on the stem – that’s OK. By removing the tips, the flowers and buds at the tip of each stem will be removed-that’s OK, too.
Continue to water the plant (remember it will need water less often without any leaves). In a few days, new green leaves will begin to form along the stem. Soon it will be blooming beautifully.
INDOOR CARE: Preparing to bring the hibiscus indoors for the winter, realize the differences in light levels from outside on the patio to the inside of a house are vast. The plants natural reaction is to drop all of its leaves. The plant is not dead. Remove all the leaves, yellow and green – the green leaves would eventually fall off, removing them now saves on clean up later. Now the bare bones of the plant are visible making it easier to prune.
Use this time to shape the plant back to a v-shape. Cut any weak, damaged, or crossed stems. On the tree forms of hibiscus, cut off any leaves or branches that have tried to grow along the trunk or at the base of the “tree.”
During winter months, as new branches grow, they will be elongated and “leggy.” When the branches are about 8” long, cut them back half way. This will encourage a full, bushy plant. After the danger of frost has passed, the hibiscus can be moved outside. Place the plant in a shady location for a few weeks to allow the leaves to acclimate to the higher light levels. Plants can suffer from sunburn, too.
WHITE FLY are small white insects that fly when disturbed, but usually cling to the undersides of leaves. The eggs they lay under leaves turn into tiny larvae that become another generation of white fly adults in 2-3 weeks time. Bon-Neem Insecticidal Soap sprayed on the undersides of the leaves can be effective in killing white fly adults. Systemic houseplant insect control is applied directly to the soil. Repeat applications as necessary. Follow label direction for application.
APHIDS are small, soft bodied insects that are often greenish in color. Aphids are sucking insects usually found on tender juicy parts of the plant such as flower buds and new leaves. Infected leaves are puckered and curled. Aphids tend to be most problematic from late May to early June and again in early August.
SPIDER MITES are sucking insects, too, looking like dark spots on the underside of leaves. Often going unnoticed until webbing is noticed on the plant, by this time the population of mites is epidemic in proportion and the plant will show signs of stress like dropping and yellowing of leaves. Since spider mite control is difficult, early detection is important.
Once a week, hold a piece of clean, white paper under a branch and tap the branch strongly several times. Wipe the palm of your hand across the paper. Reddish colored streaks across the page indicate spider mites.Spider mite reproduction is greatest when temperatures are 80ºF and above. Spider mites do not like water. A daily shower with a forceful hose can knock them off leaves and decrease the temperature in and around the plant.
Leaf scorch is one of the most common problems for hibiscus. It is caused by sun or wind burn and is first noticed in the spring after the plant has sat indoors all winter. After a few hours the leaves have brown splotches and are curled up. Just like people, plants need to gradually get used to a higher intensity of sun. Position a plant in a shady area for a couple weeks, and then gradually increase the plant’s sunlight exposure one hour a day. This way the leaves will thicken and become acclimated to the new environment preventing leaf scorch.
Another form of leaf scorch occurs in the summer on hot windy days. The browning edges of leaves – leaf margin burn – is caused when the leaf loses more moisture to the air than the roots can supply, or the stem can transport. To prevent this, water the plant more frequently on windy days; shower the foliage with a gentle mist to cool the leaf temperature; and move the plant to a shaded area out of the sun and out of the wind.
Flower blight is a slight problem in wet seasons caused by a fungus that thrives under cool, moist conditions. The best method of control is to remove all spent blossoms as soon as they start to decline. Hibiscus flowers last only one day anyway, so this can be done on a daily basis.