Hibiscus Tree and Plant Care: Leaves Turning Yellow, Fertilizers, and Pruning

Hibiscus plants are famous and grown by many gardeners for their large, showy flowers, while some are familiar with the plant due to its flowers’ medicinal properties when served as tea. Hibiscus is one of my favorite flowering plants, along with these plants that bloom purple flowers. These plants are originally native to tropical areas like Hawaii, Mauritius, Madagascar, and Fiji. Now, you can find other hibiscus species even in subtropical and temperate regions, grown either in pots or out on the lawn. With over 200 species, it’s easy to get confused about which hibiscus is best for temperate zones and which thrive in tropical zones. For you to easily determine which hibiscus plant will grow best in your area, we’ll focus on tropical hibiscus and hardy hibiscus plants.

Tropical hibiscus, as its name suggests, thrives best in hot, humid areas and cannot withstand cold temperatures. It is best to grow tropical hibiscus in Zones 10 and above, or shelter this plant indoors or in a greenhouse, if you live in Zone 9b. These plants produce bright blooms that vary in color, from red, orange, yellow, pink, purple, and white, among many others. Their foliage is glossy and has a deep green color throughout the year, perfect for their growth under the heat and of the sun in tropical areas. One of the most famous tropical hibiscus is Hibiscus rosa-sinensis L., commonly known as Chinese hibiscus, grown as an ornamental plant in both tropical and subtropical areas. This bushy evergreen perennial shrub is native to East Asia and has various cultivars and hybrids that produce beautiful blooms as well.


Chinese hibiscus
Image source: World of Flowering Plants

Hardy hibiscus, on the other hand, can be grown in temperate zones. These plants are relatively easier to take care of because they can tolerate cold climates, withstanding the chilly air of winter even in Zone 4, as long as it is protected from the harsh frost. Some of the famous hardy hibiscus species include H. syriacus (also known as “Rose of Sharon,” “Korean Rose,” or “Althea”) and H. moscheutos (also known as “Rose Mallow” or “Swamp Rose”).

H. syriacus is a deciduous perennial shrub that can grow up to 13 feet tall, with pink, purple, blue, or white flowers that are short-lived and fall within the day, but the shrub continuously blooms during late summer or early fall. As a deciduous plant, its leaves drop once a year but comes back as a full hibiscus bush during spring.


blooming hibiscus bush (Rose of Sharon)
Image source: Proven Winners

H. moscheutos, on the other hand, is an herbaceous perennial plant that is native to North America. Its thin showy flowers, named “dinner plate hibiscus,” are 8-7 inches in size and bloom in different colors, such as blue, pink, red, and white, depending on the plant variety. As an herbaceous plant, its stems die back to the ground each year during winter and grows back during spring.


red Rose Mallow hibiscus bush in full bloom
Image source: White Flower Farm

These perennial hibiscus plants can live for more than two years, regenerating yearly during spring from protected buds, bringing you colorful blooms for years every late spring without much fuss.

Growing & caring for it

It’s a given fact that you should plan your gardening efforts based on the hardiness of the plant. As mentioned, tropical hibiscus cannot handle cold and requires hot, humid areas, while hardy hibiscus can survive in cool climates. Thus, it’s less of a hassle to grow hardy hibiscus if you’re in a temperate region. Some people, however, are fine with growing tropical hibiscus as an annual plant, with the plant’s life cycle ending once the frost settles in.

Once you’re decided on which type you want to grow, it’s time to familiarize yourself with the growth requirements of these plants, so you can fully enjoy their daily bloom from late spring to summer.

SOIL

The easiest way to start your gardening journey is to buy hibiscus transplants from a nursery instead of growing hibiscus from seed. However, if you want to start growing from seed, you should sow your seeds indoors using a sterile potting mix a few weeks before the last frost. Follow the instructions in your seed packet. For more detailed instructions, read this article wherein we discuss how to grow plants from seeds.

Prior to planting, it’s important to check the pH and type of your soil. Hibiscus plants prefer slightly acidic soil, with a pH range of 5.5-7.5. If your soil is too alkaline, incorporate peat moss into your garden soil to increase its acidity. You can do this by adding 2-3 inches of peat moss on top of your soil and working it into the topsoil of your garden bed. For optimal growth, aim for a pH range of 6.0-6.5, since hibiscus thrives when planted in soil with this pH range.

Plant your hibiscus plants in well-drained soils since stagnant water will promote root rot and will cause your plant to wilt or get diseases. However, keep in mind that some varieties like H. moscheutos prefer wet soils, which is why it garnered the name “Swamp Rose.”

TEMPERATURE AND HUMIDITY

Hibiscus plants flower best when grown in humid areas with a temperature range of 60-90°F. For hardy hibiscus, when winter is approaching and the temperature drops to 32°F, you should transfer the plants indoors if they’re grown in containers. If you’ve planted perennial hibiscus outdoors, it will die down into the ground during winter, but you don’t have to worry since the plant will revive during spring.

However, for tropical hibiscus, when you notice the temperature nearing 55°F for a few nights, move your plant indoors since a temperature lower than this can kill the plant. Also, make sure to mist your plant when the temperature exceeds 70°F since too much heat may dry out the plant—remember that tropical hibiscus thrives in humid areas.

Of course, this temperature rule extends to the water you use for your plants, too. Especially for tropical hibiscus, it is important to never expose your plant to temperatures that they cannot handle, whether it’s the room or water temperature. Take that extra step towards the faucet that can give you warm water, or let that tap run until you get the right temperature, so your snake plant won’t suffer during watering. Make sure that you have a good hot water recirculating pump system in your home and an appropriate heater, such as waste oil heaters, to provide the environment to your hibiscus plants even during winter.

How do I take care of hibiscus in the fall and in winter

As mentioned, you should bring tropical hibiscus inside once the temperature drops to 55°F. For perennials, not all varieties of hibiscus can handle the winter season outdoors; these plants still need to be transferred indoors when the temperatures reach below freezing. These varieties are better off planted in containers or pots for easy transfer indoors.

To prepare your hibiscus plants for winter, prune up to a quarter of the new growth in fall. Remove all pests and insects, such as fruit flies, from the plant using either neem oil or spraying the plant with a strong jet of water (but not too strong to damage the plant). For potted hibiscus, just move the pot indoors. For hibiscus grown directly in the soil, you will need to dig it up and repot it into a container. Make sure to use a soilless potting mix to avoid bringing in soil-borne diseases into your home.

Once indoors, make sure to provide proper light and water to tropical hibiscus. Place it in a sunny window and use heating mats. If you don’t have a good amount of light shining through your window, make use of grow lights. You will need to tone down watering once your plants are indoors during winter since the weather is cool. In contrast to tropical varieties, perennials will go into a dormant state during winter will require a cool, damp location.

You will know which perennials can handle winter temperatures below freezing based on their hardiness, and these plants are the ones best planted directly in the ground. Just make sure to protect the roots with 3-4 inches of mulch, so come spring, the plant will revive with no problem at all.

The same way you’d take care of your extension cords or cassette toilets, there are simply some instructions to follow when it comes to Hibiscus. Check out our guides on amp wire sizing and SAE to metric conversion, too, so that you’ll use the right cord for the job.

LIGHT

Hibiscus likes full to partial sun, but during the summer, when the sun gets too intense, there is a risk of damage for your plant. So if you live in a tropical region, aim for an area in your lawn that will not be too exposed to the blazing afternoon sun. However, if you live in a cooler temperate region, it is alright to plant your hibiscus plants where the light during noon will reach them. Make sure that your hibiscus plants are receiving around six hours of direct light daily.

When growing hibiscus indoors, you should situate the plants in a room with southwest facing window, where they can get enough direct light daily. If the sunlight cannot reach far into your room, it will be best to situate your potted plants on a multi-layered shelf, giving them enough space to be exposed to direct light without blocking other plants. If you’re worried about mold or fungi infestation in your shelves due to the chances of it getting wet while watering your plants, then I suggest you use a shelf made up of a material that won’t allow fungus growth that easily and can withstand humid conditions, which these plants prefer. One example is this marine-grade plywood, which can survive repeated contact with water, made up of high-quality wood that is cross-laminated, held together by waterproof glue. And while we’re on the topic of making shelves, you might be interested to check out portable bandsaw sawmills and wide belt sanders that can make woodworking much easier.

If you’re doing well with providing your hibiscus plants the amount of light that they need, they will consistently produce flowers every day during its blooming season. Lack of bloom signifies that your plant is not getting enough light; plants prioritize other growth or functions over flower production (reproduction stage) if the environment is not favorable.

WATER

Tropical and hardy hibiscus differ in water requirements. Since tropical hibiscus is grown in warmer (and sometimes drier) areas, you’ll need to water it more frequently, ranging from once to twice a day, depending on the heat and humidity. This is why your hibiscus must be planted in well-drained soil since frequent watering is needed, and you don’t want stagnant water to accumulate, which will encourage root rot.

However, in temperate regions, make sure to adjust your watering schedule based on the temperature. Water your plant once to twice a day during summer. Your plant needs less watering when the weather is cool, since moisture is retained well in lower temperatures. Always check if the soil is dry to the touch before watering during fall and winter.

If you’re a seasoned gardener or a dedicated hobbyist, and you have a lot of plants to attend to that need frequent watering during the summer, you might want to check out these fuel transfer tanks that you can use to store not only fuel but also water and fertilizer. These tanks will be especially useful if growing plants is your business, and you have more than one garden or nursery to take care of.

Why do their leaves turn yellow (and how to avoid it)

When hibiscus leaves turn yellow, this is a sign that you’re overwatering your plant. To avoid this, tone down watering during cool weather, and only water your plants when the soil is dry to the touch. But if you’ve already adjusted your watering appropriately, yet the leaves are still turning yellow, there might be an issue of stagnant water around your plant. If your hibiscus is planted outdoors, try to have an irrigation system that will drain excess water, and if your plant is in a container, make sure that its drainage holes are not clogged.

FERTILIZER

As a flowering plant, hibiscus needs fertilizers to support their blooming process. Unlike other plants that do not require much fertilizing, it is important to supply your hibiscus plants with a well-balanced liquid or slow-release fertilizers. However, remember to never overdo feeding, especially during winter when perennial hibiscus is dormant. Overfertilizing may lead to toxicity and burning of roots.

Best fertilizer

Hardy hibiscus requires a lot of potassium, a moderate amount of nitrogen, and only a low concentration of phosphorus. You can opt for a fertilizer with an NPK ratio of 9-3-13 or 17-5-24 for your hibiscus plants. If you’re using diluted liquid fertilizer, only feed your plants once a week. On the other hand, you only need to apply slow-release fertilizers four times a year: during early spring, after the first bloom, during mid-summer, and during early winter. If your soil is fairly rich in nutrients to start with, lessen your feeding up to only twice a year, during early spring and at the end of summer.

PRUNING

Hibiscus plants do not really require pruning, but doing so will encourage more bloom and a bushier plant since new branches will grow. Although you won’t want to use a lawn tractor for it. Here’s how to do it. 

When and how to prune

For tropical hibiscus, it is best to prune in the fall or early spring. Trim the growing stem tips to encourage more growth. If you prune too late in the season, do not cut too far back on the stems. Always prune dead, broken, or diseased branches, and only trim just enough branches to make the shrub less crowded to let in more light. During summer, you’ll see your hibiscus thrive with more flowers and a fuller bush.

On the other hand, since perennial hibiscus dies down during winter, you can prune the plant down to the ground in fall, preferably six inches above the ground. No need to worry since the plant will revive in spring. When the plant has revived, you can also prune it just before the blooming season in early spring, trimming growing stem tips for more flowers.

Taking care of your Hibiscus is important the same way we take care of the ozone layer with the Montreal Protocol, or the same way you’d take care of a three phase engine, or your purple flowers

Propagating

To propagate hibiscus, you can use stem cuttings or seeds, albeit the former one is much easier to and faster to grow. Check this article to learn how to grow seeds into plants.

Propagating hibiscus plants via stem cuttings

  • In spring, cut a section of a stem that has not fully matured yet (e.g., with leaves but no flowers), around 4-6 inches long. Make sure that there are no flower buds in the stem cutting (trim any flowers if you see one).
  • Prepare a sterile potting mix in a container, moist it, and make a shallow hole. Place the stem cutting in the groove, water the cutting, and gently pat down the potting mix around the stem. Cover the setup to create a greenhouse effect.
  • Place the pot in a warm area (60-90°F) and out of direct sunlight. Keep the soil moist until the cutting takes root.
  • After eight weeks or so, you should see new leaves and your stem cutting properly rooted in the potting mix.

Growing them in a container

If you don’t have enough space outside your home, or you’re growing a species of hibiscus that cannot survive winter, then it will be easier to grow your hibiscus in a container. Here are a few reminders if you’re planning to grow hibiscus in pots:

  • Pick a container that has proper drainage holes and use a well-drained potting mix. It will be better if you use a soilless potting mix to avoid exposure to soil-borne diseases.
  • It is better to use stone pots instead of clay pots. The latter can make the soil alkaline over time, and since hibiscus prefers slightly acidic soil, you should avoid clay pots.
  • Newly planted hibiscus transplants or stem cuttings must be kept away from direct light for the first two weeks so they can adjust and take root properly. Once the plat is well-established, place the container in an area where the plant can have six hours of direct light.
  • Feed your potted plant with liquid fertilizers weekly, or use slow-release fertilizer that can last up to six weeks.
  • Water your plants only when the root is dry to touch in winter and fall, but water more frequently in summer (once to twice a day).

If you’re looking for more plants to grow that are easier to take care of compared to hibiscus, I have a few suggestions for you:

  • You can check out Sansevieria or snake plants, which are plants that can thrive indoors, surviving even in low to medium light and needing only minimal watering (once a week or every two weeks). There are cultivars of snake plants that can easily fit on your desk, growing only up to 6 inches tall, while there are also varieties that can grow up to 4 feet tall. These plants can remove toxic pollutants in your home and are featured in a clean air study conducted by NASA. We also have a guide on cucumber leaves.
  • If you want another outdoor plant that can give you shade and bloom, check out these dwarf shrubs that are fairly easy to maintain. You can pair both non-flowering and flowering perennial dwarf shrubs with the hibiscus plants in your lawn for a wonderful and balanced bloom during spring through summer.

Making a microclimate

If you plan to grow and propagate a lot of tropical hibiscus plants (whether for business or as a hobby) but the climate in your area is not suitable for it or your home cannot shelter any more plants, then it will be best to exploit microclimate and make use of greenhouses to shelter your plants.

A microclimate is an environment within a restricted area that differs from the surrounding area, wherein your plant can thrive in. Exploiting microclimate can be done in numerous ways. For example, you can use grow lights as a source of heat and light indoors, or you can use greenhouse covers or humidifiers to increase moisture and humidity. It will be best to build a nursery in a greenhouse so you can shelter more plants.

If you plan to do this, make sure to use materials that will not easily rot nor get infested with molds and can withstand hot temperatures and humidity, such as this marine grade plywood that I mentioned earlier. Of course, wood is not the only thing that you will require to build a proper greenhouse. You might want to check out this plasma cutter that can easily cut through stainless steel, steel, aluminum, brass, copper, and even conductive materials with high precision. And since you’re still setting up a new greenhouse, power sources may not be readily available at the start. Check out this portable engine-driven welder that you can take anywhere so you can weld anytime, even without an external power source.

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