In recent months, gardening has emerged as a leading pastime for many people in lockdown situations all over the world. For people living in urban areas with small garden areas, or those in apartments and condominiums whose only outdoor space is a small balcony, container garden can be a great option. And, while vegetables and fruit are a common choice for many this year, beautiful flowering plants create a lovely and cheerful backdrop for those who may be feeling stuck in their homes.
The tropical hibiscus (Hibiscus rosa-sinensis), though it requires a lot of attention and monitoring, can be easier to grow in a pot than directly in the garden – and can be moved indoors in colder climates should the temperature drop.
These tropical beauties can bring an exotic look to your space, and their bright, colourful blooms can attract butterflies and even hummingbirds to your garden. But, taken out of their tropical climate, hibiscus need a certain amount of care to help them thrive. In this article, we’ll cover everything you need to know about caring for your potted hibiscus – soil, water, food, and more.
Choosing the Right Varietal
Any type of hibiscus can be grown in a container – though tropical cultivars are the typically the best choices. There are a few considerations to keep in mind: some of the more rapid growers can quickly overrun their containers, some hibiscus types are more sensitive to changes in the soil pH, and others are far less tolerant to overwatering.
If you’re unfamiliar with the species, ask the staff at your local nursery to help you choose a type of hibiscus that has a proven container-grown track record.
If possible, choose a young, thriving plant with shiny dark green leaves and thick stems. You may also begin with a cutting from an existing hibiscus – trim a soft branch with leaves at the end to about 4”-6” and place it into the soil, covering in with a bell jar or portable greenhouse unless it takes root.
You could also begin with seed – though this is more difficult as the conditions need to be just right for your seeds to germinate and flourish.
Choosing the Right Pot
While hibiscus like moist soil, the tropical varieties aren’t fond of excess water. This means that you’ll need to choose a pot or container that drains well, preferably with a tray beneath so that you can monitor the amount of water your hibiscus is taking in.
If you purchase your plant from a nursery, it’s likely to be in a 4L or 8L nursery pot made of black plastic. There are a couple of reasons why you should repot your hibiscus if possible:
First, because the dark plastic can heat up enough in the sun to damage the roots of your plant, so you may wish to choose a lighter coloured container or one made of a different material – and while many growers are choosing molded plastic pots, stone is the best choice for a hibiscus plant because they are more stable and, unlike clay, will not cause the soil to gain alkalinity over time.
Remember when shopping for your new container that hibiscus require excellent drainage – so unless you, or someone you know, can drill extra holes in the base of the pot, you should choose one with at least 3-4 holes already in it. Another option would be to place a well-draining plastic pot inside a larger clay or stone pot and filling the gap with stones – stabilizing the plastic container and preventing it from overheating in the sun.
Another consideration is the size of the pot: hibiscus don’t typically mind slight crowding at the roots, so choose a pot the same size or slightly larger than the current pot. In fact, many hibiscuses will thrive and grow large in a container with a 10” diameter and young plants can be started in even smaller pots – these plants will bloom best when they’re underpotted, and may only need to be moved every 2-3 years.
If you’re unsure if your container is large enough, tilt the plant out of the container if you can, and check to see if any of the roots are wrapping around each other – this is a good sign that your hibiscus is ready to move to a bigger container. The best time to repot is in the late winter while your plant is dormant – usually in late February or early March.
Choosing the Right Soil
As mentioned earlier, great drainage is the key to growing healthy and beautiful hibiscus. Choosing the right potting soil – one that protects and nurtures the root system – gives your plant the best chance to thrive. Many growers use a standard commercial potting mix, and some prefer to blend their own soil mixture.
Be sure that your soil mix is designed specifically for potted plants – products intended for garden beds, compost blends, or mulch may retain too much moisture for hibiscus.
Thought they like to have water flowing over their roots, you will need to choose a soil mix that allows for excellent drainage as hibiscus don’t like to be overly wet. They also prefer the soil to be slightly acidic – if necessary, adding peat moss to your container can lower the pH level.
While some growers use equal parts composted bark, composted manure and coarse peat with a little vermiculite mixed in, a typical mix is composed of 50% peat, 45% composted bark and 5% perlite, allowing for excellent drainage and air circulation around the roots.
Others replace some or all of the peat content with coco coir – the processed coco fibre last about twice as long as peat before breaking down, and is also less likely to pack due to overwatering.
Planting and Repotting your Hibiscus
After gently easing the root ball out of the current container, determine whether it requires a larger pot: if the roots circle the bottom or form a solid mass in the base of the pot, it’s time to upgrade.
If your hibiscus in severely root-bound, you may choose to use a pair of sterilized shears to remove up to a third of the root mass from the bottom and sides – you can then either replace the plant in its current pot, or move it to a larger container.
Place a little of your chosen potting mix into the bottom of the pot. Disturb the root ball slightly to allow the roots to spread out a little, then place it into the new container – the top of the root ball should reach to about 1” below the rim of the pot.
If necessary, remove the plant and adjust the quantity of soil in the pot. When you have the root ball well settled, carefully fill in the gaps around the sides with more of the potting mix and press down firmly but gently.
While it’s important that your hibiscus be well supported, tightly packing the soil will remove most of the air from the soil and let to over-compaction.
Choosing the Right Spot
Your potted hibiscus can easily transition between the outdoors and indoors – while outdoors in the summer, you’ll want to choose a spot that has lots of early or late day sun but at least partial shade during the sunniest parts of the afternoon (between 12:00 p.m. and 4:00 p.m.).
Even tropical flowers can’t stand many hours of full sunlight without overheating. If you live in a warm climate, your potted hibiscus can remain outdoors year-round – so long as the night temperatures remain about 10°C (or 50°F), there is no danger of the plant freezing.
But if you live in a more temperate zone and plan to overwinter your plant inside, you’ll want to prepare it for a move indoors before the temperature changes in the early autumn.
Trim your plant back by about 1/3, then wash the stems and leaves thoroughly to dislodge any insect pests before placing the container in a warm location with plenty of indirect light.
Don’t wait too long before moving your plant – if the hibiscus becomes acclimated to the cooler, more humid autumn climate, moving it indoors to a warmer and drier space can shock it, causing the leaves to yellow or even drop off. This can also make your hibiscus more vulnerable to pests as they tend to proliferate on stressed-out plants.
If you keep your potted plant indoors, you may want to use a humidifier to replicate the tropical conditions in which most hibiscus thrive.
While indoors, your hibiscus will need a lot of sunshine to grow well – place it near a south-facing window as it requires at least 1-2 hours of direct, bright sunlight daily in order to bloom indoors.
Though 6 hours of sunlight is the norm, if your cultivar has brownish flowers, it may prefer shadier conditions. Keep the plants an inch or two away from the window glass because the hot glass could damage their blooms and leaves.
At the right temperatures and given the proper amount of light, a potted hibiscus can bloom from spring through to fall.
Choosing the Right Amount of Food and Water
During the flowering season, weekly fertilizing will provide more abundant blooms – so you will want to feed your plants regularly with a slow-release fertilizer placed around the base of the plant.
Though any general-purpose fertilizer will work (10-10-10 or 20-20-20, for example), there are specially-formulated blends intended for hibiscus (9-3-13, 10-4-12, or 12-4-18). Look for one with trace elements such as iron and magnesium in order to support growth and blooming.
You may also choose to dose your potted hibiscus plants with a weak solution of a water-soluble fertilizer mix (at half-strength or less) every time you water them. Avoid over-fertilizing as excess phosphorous can be hazardous for hibiscus and may even kill your plants.
When it comes to watering, a good rule of thumb is to check the top inch or so of soil in the container – if it feels damp and slightly spongy, the soil is wet enough. If the top layer of soil feels dry, your plant needs water. Depending on the size of the pot and the growing condition, you may need to water your hibiscus every 2-4 days or as infrequently as every week or two.
Avoid using cold water. As a tropical plant, hibiscus prefers warm water – slightly under body temperature is best, so if you don’t have a thermometer to check the water temperature, you can simply touch it with your hand to ensure it’s neither too cold nor too warm.
After each watering, allow the soil to drain completely in order to prevent root rot. Water your hibiscus, then watch for the excess water to come out the drainage holes, draining into the tray beneath. Allow a little time for the roots to soak up that excess water, but if any still remains after 12 hours, you should dump it out.
If you allow your plant to go into a dormant or semi-dormant state, you’ll want to omit the fertilizer and reduce the watering schedule – the soil can get much drier between each watering, only just ensuring that it doesn’t dry out completely.
Choosing the Right Time to Prune
While some gardeners choose not to prune their hibiscus plants, so that they can bloom more consistently, regular pruning will prevent your plant from becoming leggy or overgrown.
If you’ve established the optimal indoor growing conditions for your hibiscus, with plenty of sunlight and humidity and moderately warm temperatures, your plant could conceivably flower all year. In these cases, you may wish to cut back the longest couple of branches to 2/3 of their length every 3 months or so. This will have little visual impact, while maintaining control on the overall height of your plant.
However, if you’ve allowed your hibiscus to go dormant, and it’s not flowering or growing rapidly, it’s best to wait until late February to prune your plant. At that time, cut all the branches to about 1/3 of their original length, leaving you with a compact and symmetrical plant which should begin to bloom in late spring or early summer.
Remember to also check the roots of your hibiscus every 2-3 years and prune away any solid masses of root; using very sharp, sanitized knife, slice off the bottom 1”-2” inches of the root ball. Then add enough fresh potting mix to the container to bring the top of the root ball back to the level of the pot rim, gently spread the roots and replant. The new root growth will stimulate a rush of growth hormones, leading to more top growth as well.