Growing tropical and hardy hibiscus

Facebook Twitter Pinterest Addthis

PDF | MP3 (5:00 minutes, June 4, 2015)

There are many beautiful tropicHardy hibiscus are easy to grow and require minimal careal and hardy hibiscus available through nurseries and garden centers. I (Jennifer Schutter) grow three varieties of hardy hibiscus and one tropical. Throughout the year I receive calls from homeowners regarding hibiscus. The first thing to know is the difference between the hardy and the tropical. Tropical and hardy hibiscus do not have the same requirements.

The hibiscus is a member of the mallow family which encompasses nearly 300 species including trees, shrubs, perennials and annuals. Hibiscus rosa-sinensis is the species most commonly available through nurseries, garden centers and florists. These are bred specifically for flower size and color. They make great house plants and are a wonderful addition to a summer garden. Hibiscus rosa-sinensis is not winter hardy, and therefore must be brought in before the first fall frost. The beautiful, exotic-looking flowers are short-lived, typically blooming for only one day.

Tropical hibiscus likes a rich, well-drained soil mixture. A good potting mix could contain two parts potting soil, two parts peat moss and one part perlite or vermiculite. Tropical hibiscus does not tolerate cold temperatures. It needs warm temperatures for flower buds to develop. Indoors, tropical hibiscus should be grown in a warm, sunny location where daytime temperatures are no lower than 55°F; 65° to 75°F is best for optimum growth. They require very bright light to bloom well indoors. A sunny western or southern exposure that has at least 4-5 hours of bright, direct light is best. The more light they have, the better they'll bloom, indoors or out. Keep the soil relatively moist, not saturated. Never allow the soil to dry out to the point of wilting. Fertilize plants with a balanced fertilizer such as 20-20-20 or 10-10-10.

After the danger of frost, place a tropical hibiscus outdoors, but before placing them directly in full sun, it is important to acclimate them to the brighter conditions. Begin by moving the hibiscus to a porch, then to filtered light under a shade tree and finally into the bright sunlight. Reverse the process in the fall so that the plant is indoors before the first frost. By easing the plant into the different conditions, one can prevent bud loss and minimize foliage loss.

Sometimes hibiscus drop leaves and buds. Abrupt changes in soil moisture, air temperature or drafts can cause yellowing of the leaves. Avoid excessive watering. Some yellowing is normal in spring or fall when growing conditions are in transition. Yellowing may signal need for fertilizer. If buds drop, this can be an indication that it is too hot or too cold. Hibiscus need daytime temperatures between 65°F-75°F to develop buds. Avoid drafty areas and low light conditions. The leaves on my tropical hibiscus turn yellow and drop every winter after bringing it indoors. I’ve realized this is fairly normal because it is a shock to the plant to go from outdoor conditions to the warm, dry conditions in a home. In the spring I place it outside and it forms new buds, leaves out and produces beautiful blooms by mid to late summer.

The most common insects on hibiscus are aphids and spider mites. Keep the foliage clean by washing it periodically. Use insecticidal soap or insecticides labeled for use on hibiscus if necessary.

Hardy hibiscus shrubs supply the garden with all the beauty of a tropical hibiscus, but they can withstand cold winter temperatures that kill the tropical types. Most hardy hibiscuses thrive in hardiness zones 4 through 9 with minimal winter protection. The best planting site provides a soil base rich in humus and organic matter that drains well but doesn't dry completely. Amending the planting area with compost prior to planting improves the soil quality and encourages proper drainage. Hardy hibiscus require plenty of sunlight to bloom well. Plant hardy hibiscus in full sun. Hibiscus plants don't require heavy pruning to maintain a formal shape, but some pruning helps improve plant health and can result in better flowering. Remove winter-damaged and dead stems in late winter or early spring. In frost prone areas the stems usually die back to the ground but the roots survive and the hibiscus quickly grows new stems in spring. Mulch around plants to hold in moisture and to provide protection and insulation for the hibiscus roots. I’ve grown hardy hibiscus for eight years and find them very easy to grow. I apply 12-12-12 fertilizer in early spring, prune out the dead stems, then watch them grow and produce  beautiful blooms in various colors.