The Secrets to Growing Hibiscus Indoors

I get more questions about growing hibiscus as a houseplant than almost any other plant. Why? Because it often behaves very badly indoors. You’ll find it’s a capricious plant under average home conditions… but still it can be grown successfully indoors.

Would you like to learn how? Well, let’s start at the beginning, that is, by choosing the right plant!

Choosing the Right Hibiscus

The genus Hibiscus in the Malvaceae (mallow family) includes more than 200 species, including annuals, perennials, shrubs and trees. Most of these do not make good houseplants. In this article, therefore, I’ll cover only one species, the Chinese hibiscus (Hibiscus rosa-sinensis), by far the most popular species offered for indoor use.

This plant is of tropical origin and therefore grows best under tropical conditions. That means, in temperate climates, outdoors in the summer and indoors in the winter.

The perennial hibiscus (Hibiscus moscheutos, at left) and the Rose of Sharon (Hibiscus syriacus, at right) are two hibiscus species that should be left outdoors all year.

Among the hibiscus you should not bring indoors are the perennial hibiscus (H. moscheutos and related species) and the rose of Sharon (H. syriacus). These are outdoor plants, best left in your garden all year. I find it important to point out the difference, as many beginning gardeners presume a hibiscus is a hibiscus and bring the wrong plant indoors.

Description

What you want as a houseplant is the Chinese hibiscus (H. rosa-sinensis), so named because the first cultivars to reach Europe were sent from China. It has never been found in the wild, but botanists believe it’s not native to China, but somewhere rather further south in Asia, perhaps Malaysia or the Pacific islands.

In actual fact, the true H. rosa-sinensis is rarely cultivated. Most varieties offered these days are the result of over 1,000 years of crosses often involving other hibiscus species.

The Chinese hibiscus is a shrub or small tree with woody stems from 3 to 16 feet (1 to 5 m) tall. Its evergreen leaves are shiny dark green (some cultivars have variegated foliage) and elliptic with a toothed margin and a pointed tip.

The flowers bear 5 petals, sometimes with a frilly edge, and resemble a funnel in appearance. Or you might like to think of them as looking like a satellite dish. They include a central column composed of a 5-lobed stigma and many yellow stamens.

The original petal color was red, but there is now a wide range of colors: pink, yellow, orange, white, and even, in fancy hibiscus, shades of violet and blue. Often there is a red central eye. Some varieties have double flowers.

Flowers can measure from 4 to 6 inches (10-15 cm) in diameter, even up to 8 inches (20 cm) for fancy varieties.

Sadly, the flowers last for only one day (sometimes 2 or even 3 days for some modern cultivars), but the plant produces others over a long flowering season, almost all year under optimal conditions.

Common Hibiscus or Fancy Hibiscus?

The Chinese hibiscus commonly sold in garden centers has relatively small (about 4 inches/10 cm in diameter), solid-colored flowers often with a red eye. They are usually single, though sometimes double. I simply call this type a “common hibiscus”. It tends to produce several flowers at once and to bloom over a long period. It is often sold without a cultivar name. Quite honestly, common varieties are probably the best choices for the average houseplant lover, if only because they bloom so much more than fancy hibiscus.

Fancy hibiscus are more striking plants, often with dinner-plate-sized, multicolored flowers. Once you’ve seen these “collector’s items”, it’s hard to resist trying one. But you might be disappointed with the results. They don’t flower as abundantly or as regularly as common varieties, often only during the summer and even then, only sporadically.

Fancy varieties are hard to find locally, unless you happen to live in the tropics where there may be specialized local nurseries. Most of us have to order fancy varieties by mail.

They also tend to be hard to root from cuttings. Sometimes the only way of propagating one is by grafting it onto a more vigorous common rootstock. And yes, they are also far more expensive than common hibiscus.

When Growth Retardants Wear Off

The typical common hibiscus sold in garden centers has been treated with a growth retardant (i.e. growth hormones). This chemical stimulates a reduction in stem length without affecting flowering. (In fact, it tends to increase bloom!) The plant then remains compact and densely leafy for 6 months to a year or more, and by that time you take for granted that this low, dense habit is your hibiscus’s natural look. You’ll then get quite a shock when all of a sudden your little hibiscus starts sending up much longer branches with well-spaced leaf nodes, leading to a much sparser appearance and turning your plant from a dense mound to a space-consuming shrub.

But of course, this is simply a return to a normal hibiscus growth pattern. Since growth retardants (Cycoel, Bonzi, etc.) are not easily available to consumers, you’re only way of controlling the growth of your hibiscus once the growth retardant has worn off is by pruning (more on that later).

General Culture

In this section, I’m limiting my comments on to how to grow a Chinese hibiscus in a temperate climate, one where it will be spending the winters indoors. This is quite different from how you would handle a hibiscus if you were growing it in the ground year long, most likely in hardiness zones 9 to 12. I’ll leave explanations on its outdoor culture to others.

The Chinese hibiscus is not an easy-to-grow houseplant. It takes some experience to grow it well and I certainly wouldn’t recommend it to a beginner. Learn how to grow foliage plants like dracenas and philodendrons and simpler flowering plants like peace lilies and African violets before you embark on trying to grow a hibiscus!

Do note that it’s best to treat the Chinese hibiscus as either an indoor plant that spends the summer outdoors or a summer plant that spends the winter indoors. Hibiscus grown indoors all year long tend to become rather wimpy.

Light

Hibiscus need a lot of sunshine to do well. During the winter, place it in the sunniest place you have, probably near a south-facing window. When the sun begins to intensify in the spring, you may find in necessary to move it back from the window, at least during the hottest hours of the day. But in any season, it will always need bright light to bloom well.

If light is lacking, you can grow a hibiscus under intense artificial lighting: a 4-tube fluorescent light, for example. Use a timer to provide 16 hours of light per day. However, it remains difficult to give such a large plant adequate light: often a plant grown under artificial lighting is green and floriferous at the top, but loses most of its lower leaves.

In late spring or early summer, when the night temperatures remain above 50?C (10?C), begin to acclimatize the plant to outdoor conditions by placing it in the shade for a few days, then partial shade for a few more before exposing it to full sun.

Watering

While your hibiscus is actively growing, water it abundantly as soon as the soil is dry to the touch. Depending on growing conditions, the size of the pot and the size of the plant, that can be as often as every 4 days or as infrequently as every 2 weeks.

Don’t let the leaves wilt from lack of water! Yes, the plant will likely recover, but each time it wilts, it loses more leaves and more flower buds. If your plant is constantly wilting, it’s probably seriously root bound: repot it into a larger pot.

If you put your plant into semi-dormancy (more on that later), keep it much drier, watering it just enough so it doesn’t dry up entirely.

Temperature

Normal indoor temperatures suit this plant fine. Although it can tolerate temperatures as low as 30 or even 28?F (-1 or -2?C) for very short periods, it won’t like them. To keep yours growing all year long, you’ll need temperatures above 50?C (10?C). Many people find it easier to grow a bit on the cool side (about 60?F/15?C) over the winter, as this reduces watering needs and helps keep insect pests at bay, but that isn’t an absolute requirement.

As mentioned, don’t move it outdoors in summer until night temperatures remain above 50?C (10?C).

Curiously, despite its tropical origins, your hibiscus may drop its flower buds when temperatures soar to above 90?F/32?C). During a heatwave, it may therefore be worthwhile to move it at least temporarily to a shadier, cooler location.

Humidity

Avoid exposing your hibiscus to dry air: it’s the major cause of the bud drop so many indoor gardeners complain of and it also contributes to leaf yellowing and insect infestations. Yet the air in most homes is desperately dry during the heating season. That’s why it’s is better to use a humidifier or humidity tray to satisfy this plant’s needs over the winter months.

Fertilizing

This plant is a heavy feeder. It enjoys regular fertilization, but unless you’re growing it under artificial light, it’s still best to encourage it to slow down a bit during the winter by not fertilizing it between October and the end of February. During the growing season, use the fertilizer of your choice, reducing the rate to a quarter of the recommended dosage.

Repotting

A hibiscus blooms best when it’s a bit underpotted. In most cases, repotting into a slightly larger pot will only be necessary every 2 to 3 years. Any houseplant potting soil will be fine. The best time for repotting is late winter (late February or March).

Pruning

A lot of gardeners hesitate to prune their hibiscus since it blooms at the branch tips. It’s thus very obvious that pruning will always eliminate some of the flowers to come. In fact, it will take several months for the new branches stimulated by pruning to start producing flowers. On the other hand, you don’t prune it, it becomes overgrown and ungainly. It’s one of those “damned if you do, damned if you don’t” situations.

My recommended approach depends on your growing conditions.

If you have ideal growing conditions – high light, high humidity, moderate to warm temperatures, etc. – and therefore a situation where your hibiscus ought to be able to flower all year, make a habit to cutting back the longest branch or two to about two thirds of its length every 3 months. This will stimulate the growth of new branches that will bloom in a more distant future, yet will still leave the plant with older bud-bearing branches that will bloom over the coming weeks. As a result of this selective and gradual pruning, you’ll get bloom throughout the year on a plant whose height is still being kept under control.

On the other hand, if your hibiscus is simply holding on over the winter due to a lack of light and not doing much in the way of growth or blooming (the usual situation in most homes), wait until late February, then cut all the branches back by two-thirds. This will give you a more compact and symmetrical plant that will start bloom just in time for the summer.

Bringing Your Hibiscus Back Indoors

The worse mistake beginners make with their hibiscus is bringing it back indoors too late. When you leave it outdoors until late in the season, say until the end of September or into October, it will acclimatize to the cooling nights and higher humidity. Imagine its shock when you suddenly bring in indoors to the heat and dry air of your home! The plant usually reacts by rejecting most of its leaves, which turn yellow and drop off. It also creates a perfect situation for insect pests: they really proliferate on stressed-out plants.

Instead, bring your plant back indoors early, in late August or early September, when conditions indoors and out are approximately identical. Thus, there is no stress, very little leaf yellowing, and fewer insect infestations.

Give your hibiscus a thorough cleaning before you bring it back indoors. You don’t want any insects to come with it! For more information on this, I refer you to Time to Bring Your Houseplants Back Indoors.

Semi-dormancy

Most people have no choice other than to grow their hibiscus at room temperatures, but if you have access to a barely-heated room, one that stays about 40?F (5?C) all winter, even if it has no lighting, you can force your plant into a sort of semi-dormancy that will at least keep it alive over the winter.

Your plant will not like this treatment and will lose almost all its leaves, but with this kind of cold treatment plus minimal watering (only water it enough to keep it from dying out completely), you can at least keep it alive until spring. Then it will recuperate when you move it to back to brighter conditions and start to water it again.

Propagation

You can multiply your hibiscus through stem cuttings, air layering or grafting, but usually only stem cuttings are used by home gardeners. Forget about growing it from any seed it produces: it won’t come true to type.

Many people complain about having trouble getting hibiscus cuttings to root… usually because they try to root them in water (an old-fashioned technique that really ought to be banned).

If you really want to succeed with hibiscus stem cuttings, here’s what to do:

1. In spring or early summer, cut terminal sections of stem about 3 to 4 inches (7 to 10 cm) in length.
2. Remove any flowers or flower buds as well as any leaves on the bottom half of the cutting.
3. Apply a rooting hormone to the cut end with a cotton swab.
4. Insert the cutting into a pot or tray of moist growing mix.
5. Cover it with a dome or transparent plastic bag to keep the humidity high.
6. Place it in a warm spot, about 75 to 80?F (24-27ºC), under medium lighting. Don’t expose the cuttings to full sun as this point or they’ll overheat.
7. When new leaves appear (and that can take from 3 weeks to 2 months), that means the cutting is rooted and you can begin to acclimate it to normal indoor conditions.

There, that wasn’t that difficult, was it?

Insects and Diseases

A stressed-out hibiscus is a magnet for unwanted insects. Mealybugs, whiteflies, aphids and red spider mites like nothing better than a weakened hibiscus plant! Therefore step number one in keeping your hibiscus healthy is to ensure that it receives adequate lighting and high atmospheric humidity. Also, cooler temperatures in winter (down to 60?F/15?C) tend to discourage pests as well.

Even when you’ve done everything right, pests can still appear, so keep your eyes open. If you see any pests, spray the plant thoroughly with insecticidal soap (not dishwashing detergent) and repeat every 4 to 5 days until you see no more pests.

As for diseases, they’re pretty rare indoors, although hibiscus grown outdoors in the tropics are subject to a few of them

For Further Information

If you are very interested in hibiscus, here are two associations you might want to join: the International Hibiscus Society (the photos on its web site are amazing!) and the American Hibiscus Society.