Tropical Hibiscus: What’s New and How to Care for Them
By Ellen Barredo
Tropical hibiscus (H. rosa-sinensis) have been a top interest with customers this year. Top requests are for single flowering plants in very clear colors or bi-colored flowers. Hibiscus has also been a top re-post on my Pinterest Page! Who can resist them? Hibiscus are in their glory right now and provide an explosion of color on the patio and porch. Several branded hibiscus programs exist for gardeners to choose from.
The TradeWinds® Hibiscus is usually grown in 6” pots and has been a ‘classic’ so to speak. They are ideal for containers and window boxes, even as bedding plants.
The ‘new kid’ is HibisQs®! This series of hibiscus has new improved breeding and the focus is on beauty and longer lasting flowers. These also are great for containers, window boxes, and used as a bedding plant.
Monrovia has a beautiful line up of hibiscus in larger sizes and even tree forms. Names like Fiesta® and Fullmoon® sound very enticing. You can see the online at www.monrovia.com.
Outdoors, hibiscus prefers good morning sun with a little afternoon shade. Providing this location will provide you with more vivid and larger blooms. If you have full afternoon sun, perhaps you could provide your hibiscus bush with a taller companion to help provide shade. Indoors, full sun is needed for hibiscus. Give good thought as to where hibiscus will be placed in the home for winter. Supplemental light may be needed if you want blooms.
A steady supply of water is essential to keep flowering hibiscus healthy looking and full of blooms through the summer. Never let the container or a Hibiscus get so dry that wilting of the plant occurs. (Take note rooftop and balcony gardeners) Dry, hot, and windy conditions require more frequent watering. This plant will benefit from the addition of Soil Moist®, a water holding polymer, into the potting media when repotting in spring to help keep soil moisture more even through the summer. Avoid standing water in the tray or container of hibiscus. Salt buildup can be a problem in container-grown hibiscus. Incomplete watering, along with fertilizers you give to the plant can result salt buildup in the soil. Accumulated salt can be removed by occasionally watering the plant multiple times in a row with clear water.
During winter months when the hibiscus is indoors, the plant will be watered when the top inch of the soil is dry to the touch. When you do water, please make sure the water drains from the tray and remove any excess water.
Hibiscus plants require extra attention in fertilizer maintenance to encourage huge hibiscus flowers. Remember, never fertilize dry soil. Water and then fertilize. Organic fertilizers such as Espoma® Palm Tone are slower acting and have less chance of burning your hibiscus. Fertilizer by giving 1 teaspoon for every 4 inches of pot diameter once a month as long as the plant is actively growing outside. Scratch it into the top of the soil evenly and water in. In addition to the granular fertilizer it will be necessary to use a liquid feed. Do not use liquid feeds labeled ‘Bloom Booster’. Look for a liquid feed that is balanced i.e. 10-10-10 or for one with a lower middle number. Liquid feeds are more quickly available to the plant and can be applied every two weeks while the plant is actively growing. If you have yellow stunted new growth on your hibiscus, a little extra boost of micro nutrients might be in order. Do this with caution, additional micro nutrients may be iron, sulphur, or magnesium etc. The hibiscus prefers a soil pH of 6.5-6.8.
Defend your hibiscus plants from insects by keeping them healthy and stress free. Weekly scouting for pests is a key to catching problems early. Many insects can be kept at bay by frequent strong showers of water. Soap sprays have been successful for me and have not seemed to harm my hibiscus foliage. Hibiscus can be finicky about chemical insect sprays as the sprays can burn foliage. Read the label of any product before you use it on hibiscus!
Pruning in general for us here in St. Louis probably occurs in fall as we prepare to bring the plant in for the winter. When trimming your will remove any crossing branches, and weak or damaged branches. Use a sharp hand pruners cutting cleanly and at an angle. The point is to open up the plant so that air and light can pass through the plant. After the framework of the plant is opened up you will trim the growing tips. Look at the plant, divide its height into thirds. This gives you a visual on the amount to trim off. Generally, never trim off more than a third of the plant. Fall pruning eliminates your chance of indoor winter bloom as the hibiscus bloom on new growth. You may modify and leave a few strong branches to provide indoor blooms if you have strong winter light indoors.
Potting newly purchased hibiscus or repotting hibiscus is best performed in the spring or early summer. Repotting at this time of year provides the hibiscus with excellent weather for optimum growth. The faster the plant gets established in its pot the quicker it will bloom for you. Avoid potting into an oversized container. Only go a size or two larger than the size of the original pot.
When placing a hibiscus into a larger pot, you should give ample new potting mix. I suggest using Fafard® Container Mix. It is fortified with an extended release fertilizer and water holding crystals, and is excellent to use for outdoor hibiscus containers. I mix in a Trug Tub, Fafard Container Mix, a handful or two of Espoma Soil Perfector and mix well. Follow with fertilizer schedule above.
Next place the hibiscus with a loosened root ball into the container carefully. Please fill around the sides of the root ball with the new soil mix pushing down firmly leaving no air space. Do not cover the top of the existing root mass with soil and please leave several inches from the top of the pot to the soil line for easier watering. Next, water the repotted hibiscus and do this at least several times in a row to ensure the water has wet the entire root mass. If soil has settled, please fill with the open spaces with additional soil and water again. Remember, you should see the water draining easily from the pot. If you like you can cover the soil with a top dressing of orchid bark.
Cut hibiscus flowers early in morning and they will not wilt for one day. This remarkable feature allows you to display them, without water, on your dining, buffet, or coffee table for a beautiful display.
More info can be found at:
American Hibiscus Society
The Tropical Hibiscus Handbook, Barry Schlueter
Ellen Barredo is a certified Missouri Certified Nursery Professional with more than 30 years in professional horticulture. She works at Bowood Farms and may be reached there at (314) 6868.