Hibiscus Plant Care
Saffron a few months after a full pruning
What is Pruning?
Pruning is defined as "trimming or cutting branches to improve growth and appearance." There are many different pruning techniques, depending on what you want to achieve. Some people equate pruning with chopping a plant down to the ground. For others it's nipping off the green tip of a branch. Any time you physically interfere with the natural growth of your plant, you're pruning. To make it easier, let us break down pruning into the following categories:
Pinching: This is pruning of the topmost growth tips of branches to encourage a fuller bush. You do this by nipping off the top 1/4"-1" (1-2 cm) of green growth. Pinching works best on younger plants. If you get plants from HVH, they may have already been pinched, so there may be no need for any additional pruning during the first summer.
Selective Pruning: As the name indicates, pruning is carried out on selected branches and stems. At no time are more than one third of all the branches trimmed back. This is usually the best compromise for hibiscus, as it keeps some branches undisturbed and blooming, while letting other new branches develop.
Full Prune: Here you cut back all the branches at once down to 2-3 nodes per branch. You have to wait a bit before the next flowers come, true, but this usually yields the best, most harmonious plant. If you want to grow a show plant for your garden (not to be confused with growing for show blooms!) this is the way to go. At HVH the stock plants are pruned this way as a matter of course as we harvest wood for propagation.
Rejuvenating or Hard Prune: This is only carried out on old plants with lots of dead wood and scrawny growth. You cut back rather low down, but no lower than one foot above soil level, and remove much larger branches than in a normal pruning. Hard pruning is a drastic measure for mature plants that aren't growing or blooming well. It is particularly good for those old plants that are tall with lots of sticks and stems but few leaves and flowers. A hard prune will force the plant to regrow a more compact, rounder bush.
Corrective Pruning: This means only pruning those branches that are undesirable or damaged. Pruning off dead tips or branches that have been damaged by cold is one type of corrective pruning. Another type is cutting off very long stray branches that stick out in unattractive ways, or reshaping a lopsided plant. The goal is to prune only enough to create a healthy, balanced plant.
Hard pruning for an old plant
with no bottom growth
So why prune? We all grow hibiscus primarily for the flowers. We tend to forget how important the bush is. Pruning stimulates branching and makes a fuller bush. Why is that so great? Hibiscus form buds at the end of each branch. The more branches, the more flowers. It's that simple. If that's not a compelling argument to prune, we don't know what is!
We all hate to prune our plants while they are blooming because we don't want to lose any flowers! But the long-term payoff is that pruning stimulates more side branches on your plants, and every one of these new branches will produce even more blooms eventually. That is the basic equation for pruning - some blooms now if you don't prune or more blooms later if you do. You also get the added benefit of having a better looking bush if you prune.
There are compromises luckily! You don't have to prune all the branches at once. You can selectively prune a few branches at a time, and keep some flowering branches on your plant through the blooming season. Or you can just selectively prune stray, unattractive, or sick branches. Any pruning helps the plant and produces more blooms in the long run.
When to Prune
When to prune depends on the specifics of your area and growing conditions. The main idea is to prune just before a warming trend is coming, so that your hibiscus will grow very actively, and the increasing warmth will pull them forward into lush new growth. Pruning just before very cold weather can be so stressful that it can cause severe dieback, and you can lose more of your plant than you want to. But pruning in extreme heat can be equally stressful. The very best time to prune is times of sunny, mild weather. For some of you, this will mean you can prune any time all summer long. For some of us, it means spring or fall are our optimum times for pruning. Here are some basic guidelines:
For hibiscus planted in the ground in very warm climates where winter freezing is seldom a problem, pruning can be done in the late fall. This forces the plant to put growing energy into roots first, then when spring comes, branches shoot out all over, which means a lot more flowers in the summer.
If your hibiscus are planted in the ground in an area where frost could nip any new growth, don't attempt a fall pruning. Wait until spring to prune, as soon as the danger of frost is past. The earlier you prune, the sooner you will get flowers in the summer.
If your hibiscus are in pots, and you will bring them into sunny windows inside a house, greenhouse, or windowed garage for the winter, go ahead and prune in the fall when you bring the plants inside. If hibiscus get sun, they will regrow very quickly from pruning, and your hibiscus will be ready to burst into bloom as soon as you put them back outside in the spring.
If your hibiscus are in pots, and you will bring them into a dark place, like a basement or unheated garage for the winter, wait until spring to prune. Pruning in cold, dark conditions can cause great stress to the plant. If this is your situation and you have a very short summer, you may want to do selective pruning all through the summer so that your plants can continue to flower on some branches, while you selectively prune other branches.
If you wish to do a hard pruning and cut your plant way back, you should only do this in the spring. It is the most stressful type of pruning for the plant, and needs to be done only when the warmth and sun are increasing, never when days are becoming shorter and colder.
If you have an important event coming up in your garden or yard, you will want to time your pruning around it. It will take 2-4 months after a pruning before you see flowers again on the cut branches. Also you will have a temporarily smaller, shorter, or out of balance plant until the new growth fills in. So you will need to schedule your pruning well before the date when you need your garden to look it's very best.
For those of you who are lucky enough to have a sunny greenhouse for your hibiscus in the winter, a hard pruning in January can work very well. We do this even in the coolest parts of our own greenhouse. During the day, the sun warms the greenhouse to a very toasty temperature, while at night the greenhouse protects the hibiscus from any freezing. The pruned plants sprout out with many growing points about 2 weeks after they are cut back to only 8 to 12 inches in height. As the days lengthen and warm up, these growing points increase their rate of growth and by early spring all the pruned hibiscus have nice bushy green growth. This growth rapidly develops into lush bushes by early summer, and by mid-summer the plants are in full bloom, well ahead of other plants that were pruned later.
Last but not least, for the lucky few who live in areas with little to no freezing and who have room to plant their hibiscus in their yards, no pruning at all is an option. We have seen examples in parts of coastal southern California where hibiscus were planted in the yard as small plants, and received no further care other than water and fertilizer. Over 10 years they developed into large, very full bushes with lots of branches, and with the right fertilizer, have bloomed like crazy. Even plants with bushes known to be problematic when grown in pots tend to do well in frost free gardens when given enough time to develop. We would recommend strategic, corrective pruning to speed up the process of developing shapely bushes, but in these frost-free areas, there is little or no need for major prunings, since most hibiscus will develop well over time in optimum conditions like these.
A tall skinny hibiscus can be pruned
to create a rounder, fuller bush.
First, Take a Good Look at Your Plant
Okay, you're now ready to put the pruners to the plant, but wait a minute. There is one more thing to take into consideration. As you look at the branches, you will see that the leaf nodes (eyes) point in different directions, some in toward the center of the plant, others sideways, outward, and some even downward. You may also have some branches with an almost horizontal or downward pointing growth habit. Perhaps there is a "hole" in the leaf canopy. Where you place your cut will either correct the problem or make it worse.
The general rule of thumb is to make the cut 1/4" (1/2 cm) above an outward pointing node. This works well with staunchly upright plants, as they do need to spread a little. You do want a little spreading of the branches to encourage lateral growth and increase flowering. This is how the majority of us have learned to prune and in most instances it works very well.
However, if a plant has a spreading growth habit, you don't want it to fall apart but make it more upright. "Spreading" means plants where the majority of the branches point outward at an angle that exceeds 45°. For these plants we recommend cutting 1/4" (1/2 cm) above an inward-pointing node instead. This will force new growth to become more upright.
Pruning forces branching,
which means more buds & flowers
Let's Start Pruning!
Thoroughly clean a pair of sharp pruning shears. Wipe the cutting surfaces with a disinfectant such as alcohol gel hand cleaner. Rubbing alcohol, bleach and water, or nursery products such as Physan can all be used to sterilize pruners. Take your time and leave the sterilizer on the blades. Most sterilizing materials need time to kill disease-causing organisms, so go slowly and let your sterilizer do its job.
Take a good look at the plant to be pruned. Because the new growth will start below any cut you make, you want to plan accordingly. Cutting a few inches off the top is usually not a good idea, as the new growth sprouting off the end of the existing branch will not look quite right.
Instead, plan to cut most branches back by about 1/3 or even more. The new growth that emerges will be strong and will blend in with the rest of the plant.
Choose a long or out of proportion branch to start with. Look about 1/3 of the way down the branch until you find a leaf node (eye) that is facing the direction you want the new branch to grow. Leaf nodes are dormant growth points that sit at the base of every leaf stem (petiole) where it connects to the branch. If the leaf has fallen off, the node will still be there, visible as a small indention or bump along the trunk. Up or out is usually better than down or inward facing but let the plant shape guide you.
Make the cut just above the eye that you located, leaving about 1/4" (1/2 cm) of wood between the eye and the cut.
To make a new branch grow to the left,
cut above the node on the left side.
To make a new branch grow to the right,
cut above the node on the right side.
If your pruners are sharp, the cut will be smooth and not strip the wood or bark from the stem. Try to avoid doing so if possible.
Move on to the next branch and repeat. Hibiscus are very resilient and will actually grow better after this treatment, so do not hesitate to make those cuts.
Take a final look, as it is still possible to cut the pruned branches even further back if that appears desirable for shaping purposes.
Nodes without leaves ~
any node works for pruning
Choose the node on the side you
want the branch to grow from.
Sometimes there might be sparsely leafed out areas where we want to see more growth. So we look for a sideways pointing node on one of the surrounding branches that faces toward the direction of the empty spot. This node will grow into a new branch, filling the "hole" in the foliage.
How to Hard Prune Old Hibiscus
Sometimes you may have a lack of stem growth on the bottom of a plant. This "caney" look is often a sign of an aging plant. It will not grow new branches without encouragement. This is when you may want to do a hard pruning. It might seem strange that cutting off the upper part of the stems will make the plant branch out lower down but when you do so you change the hormone flow in the plant and it will start branching.
Don't be afraid to cut far down the stem, leaving 3-4 nodes on each main branch, but don't cut closer to the ground than one foot. Be sure to leave some leaves on the plant. After a heavy pruning there should still be a dozen or so healthy green leaves to carry on the photosynthesis the plant needs. This rejuvenating process should not be carried out very often - no more than every 3-5 years. In the intervening years follow the general pruning advice above.
How to Prune a Hibiscus Tree Standard
Hibiscus Tree Standards
How to Create Your Own Hibiscus Standard
Select a plant that has one straight main stem with a minimum height of two feet.
Cut the top off the main trunk about 2-4" above where you want the "head" of your tree to be.
Cut away all lower side branches close to the main trunk, leaving only branches within 6" from the top of the main stem.
Prune back the remaining branches that will form the "ball" on top of the standard, leaving 2-3 nodes which will grow out.
Continue trimming off new growth as it appears on the main stem. Make the cut flush with the main stem so it will not regrow from that point.
As the top branches grows out, which will take 2-4 months depending on variety, pinch back the tips on the new growth, leaving 2 to 3 nodes on each branch.
Trim off overlong or lopsided growth wherever it occurs to create a round, well shaped crown. By continuing to trim away any new growth on the main stem and pruning the crown, your standard will keep its shape and appeal for a long time to come.
Stimulate New Growth
Now that you're finished pruning, give your hibiscus a healthy dose of nutrition, including fertilizer and ideally a good growth enhancer. This will help prevent any shock or distress to the plant due to the pruning, and it will also jump-start new growth at each of the remaining nodes. Keep fertilizing and treating with growth enhancer until your plant is fully leafed out, looking beautiful, and starting to bloom.
Pruning a Damaged Hibiscus
Be sure to have plenty of water-free hand cleaner with you because you will need to sterilize your pruners after every cut into damaged wood. Once you start pruning, you'll also need to collect all dead, possibly diseased wood and put it in a plastic trash bag. You want to send all bad wood off to the dump in plastic bags rather than leave it lying around where it can spread disease back to your healthy hibiscus plants.
Checking for Live Wood
First check your plants for dead stems and branches. The test is simple enough. Working from the tip of each plant stem down toward the base, use a strong fingernail or a small knife to make a small scratch test (1/4-1/2 inch long). Scrape away a tiny bit of the brown outer bark of the stem that you are not sure about and look at the color underneath. A live branch will be bright green underneath the bark. If the branch is brown or light tan, it is dead. Some dead stems may be rotten, soft and squishy to the touch. There's no need to do a scratch test on stems that are soft and squishy - they are clearly rotting and dead. Just keep working your way down the stem, doing scratch tests, until you find the point where scratching away the bark reveals bright, healthy, green plant tissue underneath. Plant tissue that is dull green with brown mixed in is not likely to live, so keep moving your way down the branch until you find a bright green patch. Now that we know where the live wood begins, it's time to remove the dead wood.
Removing the Dead Wood - Two Strategies
Deeply Pruned Hibiscus Branch
Cut has clean, white wood inside bark.
New growth is sprouting below.
The second pruning strategy is to shape the plant while removing the dead wood. You start the same way, by finding the point where the wood is clean, green, and white. Instead of cutting just above the first clean, healthy node, cut is made further down, just above a node that is pointing in the direction you would like a stem to grow. Be sure and cut 1/4 inch above the node, so that there is room for the new stem to sprout. If the cut is too high, the remaining wood above the node may rot. If the cut is too close to the node, you may remove the special plant cells that would have sprouted into the new branch. In this second pruning strategy, you remove more wood than is necessary to eliminate the dead wood. Some of what is removed will be white and clean but the idea is to force more stems to sprout lower down on the bush, to help it achieve a full and attractive appearance. You may cut away as much as 2/3 or even more of a branch in order to do this. Don't be afraid to prune back many of the stems severely. The plant will re-grow with more branches than ever before and look fuller than ever before. More branches mean more flowers, too!
Some of the dead wood on a hibiscus bush will just be twigs. Remove the dead twigs as close to the branch they were growing from as possible without damaging that branch. Throw them in a trash bag in order to dispose of them.
Finding a Suitable Node
One with a Leaf
You've Pruned, So Now What?
After cleaning up your hibiscus by removing all dead wood and pruning some branches for shape, what do you do? It will take several weeks, depending on weather, before the new growth will come back. During that time keep the hibiscus evenly moist if possible, and fertilize it at half strength once per week. If you notice any insects on the bushes, it is important to get rid of them so that the tender new shoots that are coming will not be damaged by such insects. I was surprised to find spider mites on one of my outdoor hibiscus only a few weeks after we had the freezing nights! You can use forceful water sprays such as with the Bug Blaster or apply Clean Leaf as part of a clean-up program. Applying worm castings or other soil improving materials to pots or ground is a good idea during this time. Growth stimulants such as our Wake-up Spray or Seaweed Concentrate are also excellent to use after pruning.
Hibiscus thrive on attention, and many of the cold-damaged plants from a cold winter will come roaring back to bloom again in the summer if they are given a little tender loving care as they recover from winter. As the temperature warms and summer approaches, increase the fertilizer being used, as well as the amount of water the hibiscus receive. Stay vigilant for insect attack or use routine treatments on the plants as a preventive.
That's it! Pruning hibiscus is not a difficult job, and will produce fantastic results in terms of plant shape, health, and increased blooming. Just follow the simple steps above, and choose the best time of year to do it according to your local weather conditions.