How and When to Prune Hibiscus Plants
Do your hibiscus plants need a good pruning? Maybe you aren't sure when to prune them, or how it's done without causing damage to the plant? In this article, gardening expert Melissa Strauss shares how to prune hibiscus properly, and the best times of year to get it done.
Hibiscus plants have some of the largest flowers around. With some varieties producing dinnerplate-sized blooms throughout the summer, there is little mystery as to why these plants are so very popular. Their big blooming habit, paired with their hardiness and relative ease of care, makes them a favorite among gardeners all over the United States and beyond.
As is the case with most flowering perennials, hibiscus plants benefit from a regular pruning cycle. These showy shrubs bloom on new growth, so the objective for caring for them should always be to encourage branching and new growth. Since pruning encourages new growth, this is what will make your hibiscus produce the greatest number of flowers.
When considering how and when best to prune hibiscus plants, we need to look at their growth and blooming seasons. Since there are different types of hibiscus plants, the answer to when and how hibiscus should be pruned differs a bit.
Let’s discuss the differences between the types of hibiscus plants. Then, we will dive into our discussion of when and how hibiscus plants should be pruned.
Step 1: Identify Your Hibiscus Type
Determining the type of plant you have is important because not all hibiscus plants can be planted in the ground in climates that experience freezing temperatures.
Many nurseries lump all hibiscuses together, not giving an indication of whether the plant can thrive outdoors in your particular climate. Typically, you can search for the variety by name to determine what type of plant you have.
Hibiscus plants fall into two basic categories, each with different growth and blooming habits. Cold hardy, or deciduous, hibiscus plants such as H. syriacus lose their leaves in the fall and die back. H. rosa-sinensis is a tropical species that grows much larger and is evergreen in warm climates.
There are more species and varieties of deciduous or cold hardy hibiscuses, which makes them easy to find. Most hibiscus plants native to the United States are deciduous types. Most deciduous hibiscuses are cold hardy to zone 4 or 5 and can tolerate summers in zones 8 or 9.
Deciduous hibiscus species typically do not grow to be very large, as they die back in the winter when left outdoors. They can be more compact at about 4 feet tall or around 8-12 feet high for some varieties.
Flower color and formation are good ways to tell the two hibiscus types apart. Deciduous hibiscus flowers typically have a single-petal formation and bloom in red, pink, white, or lavender. Some varieties have a contrasting eye in the center of the bloom.
Deciduous hibiscuses typically have medium green to deep purple, heart-shaped leaves with serrated edges. There are also some deciduous types with leaves that resemble maple leaves.
Tropical or evergreen hibiscuses tend to be very popular for their bright colors and glossy foliage. They are generally thought to have originated in Asia. These are also widely available at most plant nurseries or superstores. If you live below zone 9, tropical hibiscuses must be brought indoors for the winter. Otherwise, they will die off completely.
These hibiscus shrubs grow to be much larger than deciduous types, as these do not die back each season. You can see these get up to around 8-15 feet tall in some instances, especially when they are left overgrown and not pruned.
Nearly all double-petal form flowering hibiscuses are tropical. Only tropical hibiscuses come in shades of yellow and orange, including salmon and peach shades. They also come in other bright colors, such as varying shades of pink, red, purple, white, and multi-colored.
The leaves of tropical hibiscus plants are glossy and deep green, usually with a serrated edge. These shiny leaves will not come in deep colors, such as burgundy, as deciduous types do.
Step 2: Gather and Sanitize Tools
A sharp pair of hand shears will typically be the only tool you need for pruning a hibiscus. If you need to cut through some larger branches, a small hand saw could be a useful tool as well. The most important factors for tools are that they are clean and sharp.
If you prefer to use loppers for larger branches, these work just as well as a saw. If you are hard pruning, you may need one of these tools, as hand shears probably won’t cut through very thick branches.
Clean cuts heal best, and clean tools prevent the transmission of pathogens from one plant to another. I am guilty of picking up whatever tool is on hand to do some spontaneous pruning. So, I can tell you that while this occasionally works out just fine, it also can have some very sad results. Hibiscuses are not especially vulnerable to pests and diseases, but they are not impervious either.
Cleaning your shears with alcohol gel before each use will keep the blades clean. This will extend the life of the tools as well. Wiping them down between plants will prevent any pests or diseases from being transmitted from one plant to another.
Step 3: Know When to Prune Hibiscus
Now that we understand the growth habits of these plants a bit, the basic timing should make sense. As is the case with many flowering shrubs, timing is important. If you wait too long to prune a hibiscus, you run the risk of removing buds. This will delay blooming and may reduce the number of flowers produced.
All types of hibiscus plants can be lightly pruned in the late summer. Tidying up the ends of branches and removing any diseased foliage will keep your plant looking and feeling its best. The idea here is not to encourage new growth. It is simply for aesthetic purposes and should be done early enough in the year that any new growth does become sturdy before winter.
For the most part, the bulk of your pruning should take place in spring, before the plant begins its next growth cycle. If you miss the ideal pruning window and your hibiscus is already sporting new growth, you can still prune. This will cause fewer blooms or possibly a later blooming time, but it will not damage the plant or keep it from setting buds altogether.
When to Prune Deciduous Hibiscus
Cold hardy hibiscuses are only truly hardy at the roots. They will die back in winter, commonly down to the ground. Pruning deciduous hibiscus plants is a bit more complicated, as they can be pruned in both the fall and spring. The best times to prune are just after the leaves have fallen, and just before they come back.
Because these plants die back in the winter, there is no hard and fast rule that says you must wait until spring to prune them. The roots will be unaffected by pruning, and the bare branches can be unsightly in the winter garden, so removing the old branches in the fall is perfectly ok.
In the spring, new branches will grow from the roots, and the old branches will have to be removed for aesthetic reasons anyway. So, whether you cut them back in spring or fall doesn’t matter. There will be some pruning to do in the spring though, as new branches appear.
When to Prune Tropical Hibiscus
Tropical, evergreen hibiscuses should be pruned in the spring, to avoid damage to new growth caused by unexpectedly cold weather, and also to encourage new growth. Hibiscuses bloom on new wood. So, while pruning tropical hibiscus is not always necessary, it will encourage branching and give you more blooms in the summer.
Step 4: Make a Pruning Plan
If you are pruning a deciduous hibiscus, the plan will typically be to remove the dead branches down to the ground. Tropical and indoor hibiscuses can be pruned to shape and thin out interior branches. This allows for greater air circulation to the plant’s interior and helps prevent pests and diseases.
Take the time to look at your plant from all angles, noticing any crossing branches or asymmetry. Identify any dead or ailing foliage that needs to be removed for the plant’s health. Don’t worry too much about reducing the size of your plant, as hibiscuses are fast growers.
Step 5: Prune According to Hibiscus Type
Now that you’ve figured out what type of hibiscus you have, and you have clean tools, you are ready to begin pruning. How exactly you prune hibiscus depends on the type, so let’s review how this is done for each.
Cold hardy hibiscuses die back, so their old branches will typically die to the ground and need to be removed. This can be done in fall or spring, depending on how you prefer the plant to look during dormancy.
If you want to hold space visually, it’s perfectly fine to wait until spring to cut back the old branches. Waiting until spring can help the plant begin its growth season robustly, but it will not make or break the plant.
It is also fine to prune these old branches in the fall before the plant enters dormancy. Regardless of the time you choose to prune, consider applying a thick layer of mulch in the fall. This will help to insulate the roots during colder temperatures and encourage your hibiscus to begin growing new branches earlier in the spring.
Spring pruning for deciduous hibiscuses will take place a bit later than for tropical evergreens. Allow your hibiscus to produce its first new branches. When they reach about 6 inches tall, pinch back the ends to encourage branching. More branches will mean a fuller, bushier plant with more flowers.
If the branches don’t fill in the way you had hoped, you can pinch them back again when they get nearly 12 inches tall. Beyond this, you risk pinching off buds which will cause your hibiscus to get a later start when it comes to blooming.
Tropical hibiscus plants don’t require pruning to bloom. They bloom on new wood, and pruning encourages new growth. So, pruning will mean an increase in flowers, as well as a general filling in of foliage. These plants can become leggy over time. Pruning once every year or two will keep foliage dense and healthy looking.
Typically, hibiscuses can be pruned back by a third without being set back for a year to recover. Some tropical varieties can grow very large, up to 12+ feet. Pruning may be necessary for these varieties in order to maintain their shape and size in proportion to the space you give them.
To maintain the size of your plant, cut branches back by about a third. Leave 2-3 nodes where the plant will produce new growth. Cut the branches just above the last node. Also, remove any crossing branches, as well as any dead or damaged limbs, both for health and aesthetic purposes.
Crossing branches tend to crown the interior of the plant, which creates an environment where fungus will feel right at home. By removing these branches, you increase the air circulation to the interior of the plant, encouraging healthier growth. Removing damaged limbs will allow the plant to focus that energy on new and healthy growth.
Step 6: After Pruning Care
You’ve pruned your hibiscus plants, and they will grow back fuller and more beautiful than before. However, doing a few simple tasks, such as fertilizing and deadheading, can really boost the growth and vitality of your shrubs.
After pruning in the spring, it is time to give your hibiscus some additional nutrients. Hibiscus will thrive on a slow-release fertilizer with balanced nutrients. These are heavy feeders during their growth and flowering seasons. A 10-10-10 or 20-20-20 standard, balanced fertilizer will work just fine for hibiscuses of all kinds.
For hibiscus plants in the ground, fertilizing every two weeks during the spring and summer will keep your plant looking its best and producing plenty of gorgeous tropical blooms. Potted hibiscuses can stand a bit more fertilizing. These can be fertilized once per week without consequence.
Deadheading hibiscus is a great practice that will encourage a greater quantity of larger, healthier blooms throughout the blooming season. Hibiscus flowers are short-lived, so you may find yourself plucking off a few spent blooms on an almost daily basis. This is a bit time-consuming, but not without merit.
Feel free to deadhead deciduous hibiscuses as vigorously as you have time. Most deciduous hibiscuses have flowers that are only open for 1-3 days each. Pinching off the spent blooms will signal the plant to apply excess energy to new blooms. It also just looks nicer to have a plant without wilted and dying flowers. It also prevents the plant from self-seeding.
Tropical and potted hibiscuses also benefit from regular deadheading for the same reason as deciduous hibiscuses. It encourages new buds to bloom and is more aesthetically pleasing. Hibiscuses will drop their spent blooms on their own in time, but there is no reason to leave them in place if you have the time to deadhead.
Hibiscus plants are sturdy plants that produce tons of large, colorful blooms. They really pack a punch and are not difficult to care for or picky about their environment. These adaptable plants bring color and charm to the garden for three seasons and year-round in the case of tropical and indoor plants.