The hibiscus is one of the most beautiful and versatile flowering garden plants you can grow. With several hundred different varieties, the hibiscus is a species that includes annual and perennial plants, woody shrubs and small trees depending on the type you are cultivating. It brooms profusely producing stunning flowers, in many different hues and colors. In this article we will look at how to grow hibiscus in detail.
Although we usually think of the hibiscus as being lush and tropical, not all varieties are. Some can be quite resilient to the cold, and in fact there are native hibiscus species on every continent with the exception of Antarctica.
Hibiscus plants can be raised indoors, but many varieties thrive in tropical or near tropical settings outdoors, blooming almost year round. Then there are the varieties which shed their leaves in the winter and emerge again in spring to bloom in late summer or early autumn.
In most climates, the best flowering time is in summer and autumn, but even those varieties that do bloom year round will experience a slow down during winter, as well as during periods of extreme heat. Flowers usually last longer and are at their best in autumn where the combination of shorter days and cooler weather can produce an explosion of color.
Because of the range in the size of these garden plants, there will be an ideal hibiscus plant for any location in your garden. You can choose from small plants right up to shrubs and small trees. Hibiscus do best when they aren’t forced to compete with other shrubs for food, water and sun, so if possible set aside an area in your garden that will contain primarily hibiscus and other smaller plants.
Choosing A Location for Your Hibiscus
Hibiscuses are plants of great beauty, so choose a location where they can stand out and enhance their surroundings. Different varieties have different growing habits.
Some require more sun than others, but in general hibiscus should be planted so that they get at least 6 to 8 hours of sun every day. The time of year when they bloom will also vary. There are varieties that will need some protection from excessive wind. These are all factors you will need to look at when you are selecting plants.
As the size of different types of hibiscus vary considerably, be sure to leave enough space both below and above ground for them to fully develop. Roots need room to spread out. If they are cramped, plant growth will be affected.
Place shrub-like hibiscus behind shorter plants and be sure they are not planted too closely together. For well-shaped shrubs, it’s best to leave enough space for the top and sides of each shrub to spread out and develop. Some varieties have a tendency to grow tall and compact, while others will grow closer to the ground and sprawl out in a wider arc.
Smaller varieties also need adequate space to grow. You have to decide whether you want the look that will come with a mass showing of hibiscus or if you prefer to set plants so that each one has its own stage.
Soil Preparation for Your Hibiscus
If you’re planting your hibiscus directly into the ground, proper soil preparation is essential to ensure that plants remain healthy and vigorous. Before planting, thoroughly weed the site. Then add a layer of compost or other organic matter and mix this into the existing soil. The goal is to have light fertile soil that drains well.
But if your soil tends to be heavy, you can still have success with hibiscus, as long as you provide good drainage. One way to do this is to build up your soil level higher. Raised beds work beautifully for this. Proper drainage is essential as the roots of hibiscus plants will rot easily if left in soggy soil. Although adequate watering is important, it’s recommended that the soil be allowed to dry out slightly before watering again.
Planting Your Hibiscus
Hibiscus, as with most garden plants, should generally be planted in spring, at the beginning of the growing season. But in mild climates, you may be able to get away with planting later on in the winter and even right through until autumn.
If you’re bringing hibiscus plants home from a nursery, give them a chance to get used to their surroundings before you transplant them into the ground. Try to put them in the ground on a warm, partially overcast day and if possible provide some shade during the hottest part of the day for the first few days.
Once you have the site prepared and the soil ready, it’s time to do the actual planting.
1. You should dig a hole that is slightly deeper and larger than the original container they came in. This oversize hole gives the roots lots of room to take hold and become well established.
2. Carefully, remove the hibiscus plant from its container or pot by holding the stem gently while tapping on the sides of the container to loosen it. Be careful not to bruise or damage the foliage in any way and handle the roots very gently.
3. Place the hibiscus in the hole no deeper than it was in the original container. Carefully place soil all around the plant. Be sure to firm the soil around the root ball to stabilize the plant in the ground.
4. Next add a layer of mulch around the plant, but don’t allow the mulch to actually touch the plant. This will help to prevent the growth of fungus. Mulch also works to reduce weeds and keep the plant uniformly moist while aiding in adequate aeration; a necessity for healthy roots.
5. Finish off by watering your hibiscus thoroughly. It’s best to use either a drip hose or sprinkler to keep the soil around the root base from washing away and exposing the roots.
6. By the way, once planted, it’s best to avoid digging in the soil at the base of the trunk to avoid damaging the shallow root system.
General Care and Tips for Growing Hibiscus
Watering Hibiscus – Hibiscus thrive in humid conditions, but you can grow them successfully in drier regions, as long as watering is done regularly and thoroughly, so roots stay moist.
Avoid frequent light sprinklings which don’t soak into the ground. If rain is infrequent, be sure to mist or gently hose off the foliage occasionally. But in general, it’s best to direct the water to the root area and keep it off of the blooms.
Fertilizing Hibiscus – Planting hibiscus in good quality, nutrient rich loamy soil, and adding aged compost and organic matter like well-rotted manure, will provide many of the nutrients these beautiful flowering plants require.
It helps greatly if this organic matter is replenished throughout the growing season, as hibiscus feed heavily, particularly while blooming. One way to do that is by regularly adding compost to the surface area around the plants.
Other types of organic matter can also be used to supplement the nutrients the plants receive from compost. For instance, materials containing potassium will promote exceptional blooms, bright colors and profuse flowering.
As a general rule, the healthiest hibiscus will be those which are fed slowly and infrequently.
Staking Hibiscus – The shallow root system of hibiscus plants is not deeply anchored. It usually has several main roots and a mass of smaller roots close to the surface. Because of this, the plants can be easily uprooted or blown over by a strong wind. Uprooting can injure the root system and if the damage is severe enough this can result in root rot.
So if they are located in an open or windy area, you may want to consider staking taller plants to avoid this problem. Hardwood or bamboo stakes are good choices. Pound them into the ground far enough that they embedded solidly. Then use soft ties to attach the stem to the stake.
Pruning Hibiscus – There are a few reasons why pruning is done. Since hibiscus will flower on new shoots, pruning stimulates budding. It also keeps plants nicely shaped and at a manageable size, and removes old, diseased or dead wood.
If or when to prune, depends on the type of hibiscus.
The time to heavily prune tropical hibiscus is generally in spring. Since pruning will encourage new growth, be sure not to do it too early if there is any possibility of frost in your area, as cold weather will damage this new growth. But you can also do some selective pruning if necessary, during the growing season.
Little pruning is going to be required for hardy hibiscus, as they die down to ground level each winter. But it’s a good idea to prune back dead material in the fall. On new shoots which appear in spring, any pruning is going to be limited to controlling the size of the plant if it outgrows its location.
Rose of Sharon can be pruned, usually in late winter or early spring, to remove the previous year’s growth. Doing this will produce bigger blooms. Since it is a multi-stemmed plant, it can be cut back to a single stem. This is what is done to create the Rose of Sharon tree. As these plants can also be used as a hedge, pruning is done in this case to shape them accordingly.
Problems with Hibiscus – Hibiscus require more care than many other garden plants, to prevent problems. Many of their problems are caused by pests or disease, but others are the result of factors which affect growing conditions.
Two common problems which may be caused by growing conditions are the yellowing of leaves and bud drop. Both can be resolved fairly easily once you determine the cause.
Before becoming overly concerned with yellow leaves, be aware that hibiscus bushes naturally shed their older leaves a few times during the course of a year. Before shedding, these leaves turn yellow. This usually occurs around the bottom of the shrub.
However, if yellowing and dropping of leaves works its way up towards the top of the shrub, there may be another reason. There could be several culprits in this case, ranging from a cold snap or an unexpectedly hot day, to excessive moisture or too much fertilizer being used around the root area. If the roots are disturbed for some reason, the plant may react by dropping leaves.
In most cases, your plant will recover in time. If there are things you can correct, like how often you water or feed, that may speed the recovery.
The other common problem is bud drop. Buds are extremely sensitive and practically any type of stress to the plant will cause buds to drop off before they have a chance to open. Certain varieties, but especially some doubles, have a greater tendency towards bud drop than others and are affected by nutritional deficiencies as well as environmental conditions.
One common stressor is providing either too little or too much water. Excessive temperature changes, and if you use a fertilizer to feed, over- fertilizing can cause blossoms to fall off prematurely, as well. Buds may also fall off if the plant is suffering from an infestation of insects. Thrips, gail midges, as well as a variety of other small insects are common culprits.
Pests That May Visit Your Hibiscus – There are a large number of insects, both large and small that can play havoc with your hibiscus plants. In general, larger insects chew foliage or blossoms, while smaller insects suck juices from the plant.
Larger pests like cabbage loopers, caterpillars, grasshoppers, or the aptly named hibiscus beetle can decimate a plant in short order, so if you notice a severe problem, you’ll want to address the issue in short order. Some of these pests can be hand-picked, but it may be necessary in extreme cases where the destruction is widespread, to take more drastic action and use an insecticide or pesticide to get the problem under control.
Smaller insects do their damage differently. Thrips are tiny insects which feed on the buds of the hibiscus causing them to drop off before blooming. Gail midges lay their eggs inside buds, causing them to turn yellow and eventually drop off. An organic insecticide, used weekly should alleviate the problem of both thrips and midges. But it will also be helpful to open up fallen buds to check for midge larvae. If you do find them, remove other yellowed buds and dispose of them away from the hibiscus plant.
Other smaller insect pests that can infest your hibiscus include aphids, whiteflies and mealy bugs. Insects like these can be controlled by spraying plants with a soap spray made by adding a tablespoon of liquid soap to a gallon of water. You can also remove most insects by spraying the underside of leaves with your hose. Spraying horticultural oil on hibiscus leaves is a good way to control aphids, mealy bugs and whiteflies as well.
Diseases That Affect Visit Your Hibiscus – Unfortunately, the hibiscus is susceptible to a number of viral and fungal diseases.
Viral Disease in Hibiscus
When your hibiscus plants are infected with a viral disease, the primary site of the problem will be in the foliage. Leaves may be cupped or deformed in appearance and they may appear to be mottled. There is little that can be done to treat viral infections. If you prune infected areas, be sure to clean off your pruning sheers with a weak mixture of bleach and water before using on other plants, to prevent the spread of infection.
Fungal Disease in Hibiscus
A couple of common fungal diseases are leaf spot, and root and collar rot.
If your plants are afflicted with a fungal disease, the leaves may have brown, black, or irregularly shaped spots on them. The best way of dealing with leaf spot is to remove and burn infected leaves and then use a fungicide on the infected plants. A less serious disorder is black mould which appears on the top surface of infected leaves. Black mould grows on plants that are attacked by the small sucking insects mentioned preciously. You can rid of this form of mold by getting rid of the insects.
Other types of fungus cause roots and at times even stems, to rot. Afflicted plants will wilt as if they need to be watered. But in fact, root and collar rot are caused by overly wet conditions. This could be the result of poor drainage, over watering or a combination of the two. The best thing to do is to try to eliminate the cause of the wet conditions. Applying a fungicide to the soil around the plant can also help.
Types of Hibiscus
The hibiscus can be divided into three main types.
The one we tend to think of when we think about showy hibiscus blooms is probably the tropical hibiscus. This is a very popular variety but should only be planted directly in the ground in truly tropical climate areas like southern Florida or Hawaii.
The most common variety that is typically grown outdoors is the hardy hibiscus. If you plan to grow hibiscus in Baton Rouge, this is the kind to plant, as hardy hibiscus will do well in zones 4 to 9.
The third type of hibiscus is the Rose of Sharon which is a multi-stemmed flowering shrub. You may have also heard this variety referred to as Rose of Sharon trees. By pruning during the first couple of seasons, you can eliminate all but one main stem. When this is done, your shrub takes on the appearance of a tree. Rose of Sharon will grow in zones 5 to 9.
The tropical hibiscus belongs to the rosa-sinensis family. There are literally hundreds of different varieties of tropical hibiscus, all of which are evergreen. They come in three designated size classifications. Tall are between 6’ and 10’; medium are 3’ to 6’ and low are under 3’.
Tropical hibiscus have deep green glossy leaves with blooms of red, pink, orange, yellow, lavender, scarlet, and white, mixed and matched with a multitude of different shades and color variations, often with more than a single color on a bloom.
Tropical hibiscus plants bloom profusely, but the flowers only last a day or two, and are then replaced by more. The cycle repeats, creating an extravagant explosion of color as long as they continue to blossom.
Flowers on these ornamental plants are generally unscented. They more than make up for that with the showy display of single, double, or semi double, five petal flowers. These blooms come in many different shapes and textures, ranging in size from about 2” to 12” in diameter.
These tropical plants need to be planted in a warm section of the garden, free from cold drafts and in a spot where they will receive sun all day long. It can be a challenge to grow these plants in cooler areas of the country. Plant them in protected areas as much as possible, for optimum results, or use containers.
Tropical Hibiscus Plants in Winter
Tropical hibiscus plants are very delicate and do not tolerate the cold well. They can be left in the ground year round, only if you live in an area with little or no danger of frost in the winter. Otherwise, they should be grown in pots or moveable containers, so they can be brought inside during cold weather.
So what’s too cold? Pots should be taken indoors if you live in Zone 8 or north of it. It’s safe to leave potted hibiscus outside in Zones 9 or 10, but plants should be covered if frost is possible. It’s best to use straw or a thick layer of mulch which will provide adequate protection. To protect all parts of your hibiscus, lay pots on their side so the entire plant can be covered.
The hardy hibiscus is native to Florida and other parts of the southeastern United States. These plants are much more resistant to both the cold and drought than are tropical hibiscus plants. They can be grown successfully in Zones 4 to 9.
Hardy hibiscus, sometimes referred to as rose mallows or swamp mallows, typically bloom from midsummer right through to early autumn or until frost hits your area. What distinguishes them from their tropical counterpart is their ability to survive freezing temperatures.
With more than 10 species and just as many hybrids, the hardy hibiscus produces a stunning display of enormous flowers primarily in various shades of pink or red, as well as white, with some flowers being bi-colored. It’s not unusual to see blooms of 6’ to 12’ in diameter.
Even though these hibiscus are not tropical, their flowers most definitely have the tropical look about them. Blooms only live for a day or two, but new ones soon come on to take their place. Although it’s not necessary to deadhead spent blooms, plants looks better if you do.
Plant sizes range from between 2 and 8 feet in height to between 2 and 6 feet wide at maturity. You can find a variety that will fit in with existing perennials in your garden or plant them on their own.
Hardy perennial hibiscus are rarely grown from seed. The usual course of action is to pick out plants at a nursery. But they are easy to grow and will be around for years once they are established in a garden.
Choose a sunny location that has some protection from the wind when planting, as they need at least six hours of sun every day and do not tolerate shade well. It’s best to plant them in rich soil with plenty of organic matter added, but they will grow in average soil conditions better than tropical hibiscus does.
This type of hibiscus needs a regular supply of water to perform at their best. They will tolerate more moisture than tropical hibiscus, and in fact wild swamp mallows are planted in marshy, very wet areas and thrive. When planting, it’s wise to space them about 2 or 3 feet apart to allow for growth and air circulation.
Hardy Hibiscus Plants in Winter
These herbaceous perennials require little care over the winter, as they die down to ground level. In late autumn after a killing frost has hit, cut back stems to about 3 to 4 inches above the ground. You can cover them with a thick layer of mulch to help protect the root ball over the winter, but it’s probably not strictly necessary, unless you are in a lower numbered zone.
As they are so late to re-appear in spring, you may want to put markers where they have been planted, so you don’t forget and dig around and damage the roots. In fact, they may not start to sprout until soil temperatures approach the 70 degree mark, so be prepared to be patient. Once it does begin though, growth will happen rapidly.
Rose of Sharon
The Rose of Sharon is another type of hibiscus. It belongs to the Hibiscus syriacus family. As a deciduous flowering shrub, it loses its leaves in the winter. Rose of Sharon bushes can be massive, with some growing as tall as 8 to 12 feet with a spread of 4 to 6 feet. Other varieties can grow to the more manageable height of 5 to 8 feet.
Flowers on the Rose of Sharon are beautiful with some varieties having single blooms and others double, with blooms varying in size but generally about 2-1/2 to 4 inches in diameter. The colors displayed are eye-catching, and range from white to red with various shades of light blue or lavender also in evidence. As with other types of hibiscus, blooms are short-lived but plentiful with fresh ones appearing daily, at its peak.
The climate in zones 5-9 is the most favorable for growing Rose of Sharon, allowing these regions to enjoy the beauty of the hibiscus in areas which experience freezing temperatures in winter. But Rose of Sharon is also prized by gardeners in the southeastern part of the U.S. because they can withstand the crushing heat of the summer and still produce abundant blooms.
Like other hibiscus, they thrive if planted in rich, well-drained soil that has lots of organic matter mixed in, but will tolerate less than ideal soil. Rose of Sharon plants really need to be planted in full sun. If grown in an only partially sunny area, there is the possibility of the shrub falling prey to fungal damage.
The Rose of Sharon is often used as a hedge, although they will only be useful for privacy in summer and early fall. But they are also very showy when used as a stand-alone shrub, or as background against a fence or other structure. Placing them behind smaller bushes or plants can hide the flowerless and leafless stalk.
One of the main appeals of these shrubs is the fact that they bloom so late in the growing season. Although late to come to leaf in spring, they are still going to be blooming profusely when most other flowering shrubs have long finished.
Rose of Sharon in Winter
Blooming stops when frost hits. Unlike many other deciduous shrubs, its foliage does not change color before it drops off.
You really have to do very little to Rose of Sharon in preparation for the winter if you are in the recommended zones. If your shrub is located in a very open windy location, you can wrap burlap around the bush and mulch with leaves around the base. But even this is not usually necessary, unless you find that your Rose of Sharon shrubs are not surviving the winter well.