Hibiscus: The Queen of Houseplants?

Has the hibiscus (Hibiscus rosa-sinensis) become the queen of houseplants, dethroning the African violet, which has played this role for almost 40 years? Judging by the e-mails I receive, it would seem so: it’s by far the plant that raises the most questions. In terms of sales, however, it’s always the African violet that tops the charts, with the hibiscus lagging far behind. The difference is that people find the violet easier: it satisfies the majority of people. Hibiscus is much more difficult to grow… hence the many questions.

Not for Beginners

First and foremost, I suggest starting with something else as your first houseplant, preferably a green plant: philodendron, aglaonema, snake plant, spathiphyllum and so on. Get to grips with these plants before moving on to flowering plants, such as African violet or phalaenopsis (probably the easiest orchid under our conditions). And when “ordinary” flowering plants no longer hold any secrets for you, try a challenging plant like hibiscus.

Why is hibiscus so difficult to grow? Because it requires 2 things that are not very common in our homes: maximum light intensity and high humidity.

Lighting and Humidity

“‘Oh my!” you say. My interior is perfectly lit! Is it really? Don’t forget that the hibiscus tolerates the full sun of the tropics without a problem: twelve hours a day of sun so intense that it melts rubber. Our sun doesn’t even last nine hours a day at the winter equinox, and it comes in so obliquely that it’s lost almost all its power.

When it comes to humidity, the air in the average Caadian home is drier than that of the Sahara! So you can imagine the dismay of a plant accustomed to 70% relative humidity when the air only reaches 10 or 15%! If your glasses don’t fog up when you enter the house, if your windows never fog up at all, even at -15°C (5°F), then it’s not humid enough for a hibiscus.

So, hibiscus has a hard time with our winters. On the other hand, it’s very happy with our summers, especially if you put it outside in the summer when the sun is really intense. And summer humidity is excellent. So the trick is to get our hibiscus through the winter, because they’ll pick up again in the summer… if they survive until then.

Sun and Humidifier

First, the hibiscus should be in front of the largest, brightest window you have, from October to April. You can add extra lighting to compensate for low natural light. A LED lamp open 14 to 16 hours a day, combined with natural sunlight, can create an “almost normal” situation.

Now, increase the humidity. The most logical way is with a humidifier set to “maximum”. Or grow lots of houseplants, as each one releases moisture. You can even enclose your hibiscus in a transparent plastic bag for the winter: this ensures excellent humidity.

Other Hibiscus Requirements

Apart from its need for full sun and high humidity, hibiscus is not that demanding. Almost any slightly acidic potting soil (and commercial potting soils are slightly acidic) will do. However, if you water hibiscus with alkaline tap water, the potting soil will become less and less acidic over time. So it’s wise to repot hibiscus annually in fresh potting soil.

Watering is child’s play: water abundantly as soon as the potting soil is dry. If it’s not dry (touch it!), don’t water! The same plant may require watering every 4 to 5 days in midsummer or when the air is very dry, and only every 2 weeks if the light is low and the air humid.

Temperature-wise, it’s easy: hibiscus likes the same temperatures as we do! Between 18 and 29°C (65 and 85°F) during the day, and a little cooler at night.

Also, hibiscus doesn’t go dormant. It needs to be fertilized all year round, even in winter. Any “complete” fertilizer (including trace elements) is suitable. However, avoid fertilizers rich in phosphorus (the middle number), as too much phosphorus is detrimental to hibiscus flowering. Fertilize at full dosage from April to September, and at half dosage in winter.

Hibiscus blooms on the year’s growth. So, the less you prune it, the more it should flower. The fact remains that the plant becomes fat and bald at the base if you never prune it. The compromise is to cut back the longer branches by a third, but leave the shorter ones untrimmed. Repeat every spring, between late February and August. This way, you’ll always have some “mature” branches that will flower, and new branches, stimulated by pruning, that will replace them in turn.

And the Bugs?

Hibiscus is almost always infested with red spiders when the air is dry. These bugs, barely visible to the eye, create small yellow spikes on the leaves, which can then fall off. Also, when they are very numerous, they create “spider threads” between the branches. Whiteflies and aphids can also be problematic. Fortunately, treatment of all these pests is simple. First, increase the air humidity (insects attack stressed plants, and dry air is the primary cause of stress in hibiscus). And “shower” your plant once a week, as long as there are symptoms of infestation. Strong jets of water are far more effective at controlling insects than even the most powerful insecticide.

Transitions

One last tip: hibiscus has difficulty with transitions and its leaves turn yellow when things go too fast for its liking. So, at the start of summer, you need to acclimatize it gradually to outdoor conditions, offering it only shade and 2 or 3 hours of exposure to outdoor conditions on the first day, a little more the next, etc. After 2 weeks, your plant will be ready to face full sun and stay outdoors 24 hours a day.

But it also needs to be acclimatized when neing broight back in. Start early, as early as the end of August, before the nights outside become cooler. Also, moving directly from the sun and humidity of the outdoors to the lower light and dry air of the house is difficult for hibiscus. Put it inside for 2 or 3 hours the first day, 3 or 4 the next, and so on. Or use the plastic bag trick: enclose the plant in a transparent plastic bag, where it will retain its humidity, and poke a hole in it every day with a pencil. When the bag is in pieces, remove it: your plant will be well acclimatized to the drier air. Also, increasing humidity helps compensate for low light levels.

And that’s it! A quick summary of hibiscus cultivation. It’s not the easiest of houseplants, but it can be grown… if you know what to do!

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Larry Hodgson published thousands of articles and 65 books over the course of his career, in both French and English. His son, Mathieu, has made it his mission to make his father’s writings accessible to the public. This text was originally published in Le Soleil newspaper on February 24, 2007.