Getting hibiscus to bloom

Hibiscus Flowers – Hibiscus Blossoms Falling Off Plant

While hibiscus flowers often grace us with beautiful blooms, these highly sensitive and temperamental plants sometimes fail to flourish. Either there are hibiscus blossoms falling off the plant or the hibiscus buds won’t bloom. However, becoming familiar with the most common causes of hibiscus flower problems can make it easier to correct the issue.

Dropping of Blooms on Hibiscus Tree

One of the most common causes of hibiscus blossoms falling off plants is insect pests, particularly thrips. Theses tiny insects feed on hibiscus flower buds, causing them to fall off prior to blooming. Using an organic insecticide once a week as directed should help take care of the problem.

Gall midge is another common pest affecting hibiscus flowers. This

insect lays its eggs inside the buds, turning them yellow and eventually causing them to drop. These, too, must be controlled with an appropriate insecticide targeted at these pests. To find out if gall midge is to blame when hibiscus buds won’t bloom, examine the fallen buds for signs of midge larvae by cutting or pulling them apart. It will also help to pick off any yellow buds and dispose of them promptly.

Other insect pests that may cause the dropping of blooms on hibiscus trees include:

  • spider mites
  • mealybugs
  • aphids
  • whiteflies
  • hibiscus beetle

In addition to insecticidal sprays, placing yellow sticky traps, which they find attractive, near the plant may help catch and eliminate them.

Other Factors Leading to Hibiscus Blossoms Falling Off Plant

Hibiscus flower and bud drop can also be the result of a number of other factors such as nutritional deficiencies and environmental conditions. Bud drop on hibiscus flowers is oftentimes associated with an underlying issue that can be easily corrected. For instance, insufficient watering, excessive changes in temperature, and over-fertilizing can all trigger the dropping of blooms on hibiscus trees. Hibiscus flowers require lots of light, high humidity, and moist soil. They also need regular feeding with fertilizer as directed.

The best way to keep hibiscus flowers healthy is to accommodate their needs and check the plants often for signs of problems.

Why do buds drop off my hibiscus?

As past president of the Australian Hibiscus and the International Hibiscus Society, there’s no one better to teach about all things hibiscus plants than 87-year-old Over60 community member, Jim Prudie.

“This is my answer to the question which is put to me by people when I gave talks and at displays ‘Why do the buds drop off my hibiscus?’.

There are many causes for this problem, and it occurs when the plants are under some type of stress, like too much water, or not enough water, especially in hot weather.

Make sure that you keep the water up to your plants regularly, and you have to be very careful in the heat that you supply enough moisture to the soil for the plants to be able to draw up enough moisture from the ground, otherwise they will drop their buds. Never allow the soil to dry out.

Over watering can also cause the buds to drop, by causing the essential nutrients to be leached from the soil, thus causing a lack of nourishment to the buds, and they fall. This can happen when we get a lot of rain and the ground is saturated.

Excessive amounts of fertiliser can also trigger bud drop, especially if you use large amounts of Nitrogen, as this will trigger a burst of new growth, and all the energy will go the new leaves and the buds will not get enough of the nutrients, and bud drop will follow.

Changeable weather patterns will also cause bud drop, especially if there is a big difference in the day and night temperatures. Rainy weather after a dry spell will often start the buds falling, as the rain acts the same way as too much nitrogen and causes a burst of new growth, to the detriment of the buds, for a little while.

Insects are a big cause of bud drop, especially the Harlequin Bug and the

Harlequin Beetle, as they suck the juice from the junction where the bud joins the stem, and this causes the bud to fall.

I have seen buds fall after people have sprayed with insecticides, especially if they use too strong a mixture.

Mulching the garden beds will help with the moisture problem in the hot weather, as it stops the moisture from being dried up by the sun, and the soil stays nice and moist and cool and the plants are not so stressed. This will be most important if our present problem of no rain.

Some varieties have this tendency to drop their buds more than other plants, and hybridisers should take this into consideration when they are choosing their

parents for their hybridising. Doubles in hot weather are known for dropping their buds, as they take so long to open, and they can be affected by all of the above symptoms, while they are trying to develop.

There can be a combination of all of these symptoms which will cause your problem with bud drop, so you have to look at fixing all the problems, if you are partly going to stop the bud drop, although in the hot weather which we get, I am afraid it is a bit of a losing battle, and it is best not to expect too many flowers in the hot weather, and be content to wait for the cooler weather to come.

I have it said to me that people think that some insect nicks the buds off, which can happen if you get an attack of the Harlequin bugs and beetles, but it can be a natural thing for the plants to do this whenever the plant is under some type of stress, and it is usually during the summer heat, and soon as the weather cools down the buds will stay on, and you will start to get more flowers.”

Related link: Jim Prudie on how to prune a hibiscus plant

Thrips

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My Buds are Falling off Before they Bloom!

What if you’ve done everything right and your hibiscus are growing well with lots of green foliage, but the buds on your plants are falling off the plants before they open into gorgeous flowers? Well, you probably are experiencing the scourge of flowering plants – the lowly thrip.


Healthy Hibiscus Buds

Identifying Thrips: Thrips are insects that lay their eggs inside the buds of hibiscus, roses, and other species that make big buds before flowering. The thrip is small but visible if you look for it. The easiest way to see thrips is to take an open flower and shake it over a white piece of paper. Thrips will fall out of the flower onto the paper, looking like small, black pencil lines on the paper. They are much longer than they are wide, and their dark color stands out against a piece of white paper.


Off-Color Bud
Infested with Thrips

Bud Drop: The typical sign of thrips is a bud that grows large, turns an off-color before opening, and then falls from the plant at the slightest pressure. Buds may sometimes fall before turning color, but often that sort of rotten color happens before the buds fall. The reason for this change in the big, healthy bud is that the thrips have been scratching around inside the bud as well as laying eggs inside of it. When the bud falls, the young thrips are then able to leave the bud and burrow into the ground where they change into adult thrips that are capable of flying back up to new buds to continue the cycle.


Thrips Scratch Marks on a ‘Bon Temps’ Hibiscus Flower

Scratch Marks: Some varieties of hibiscus do not react to thrips by losing their buds. In that case you can see the thrips damage as scratch marks on the flower petals. Sometimes it looks almost natural, like the spots and markings that some of our varieties produce as part of their interesting flower coloring. Other times you can see how it badly mars the beauty of the flowers. Even though these varieties do not lose their buds they can still be treated in order to obtain flawless blooms free of thrips scratches.

Treatment: Fortunately, there is a simple and effective treatment for thrips. For fast and full results, it is best to remove all rotten buds from the plants and the ground and dispose of them in the trash. In order to keep thrips under control, you will need to use a product called Spinosad. This chemical needs to be sprayed over the tops of the plants, covering the buds and upper leaves of the plants. Use Spinosad for three treatments, 5-7 days apart. Each treatment will dramatically reduce the number of thrips and increase the number of flowers that open normally. Three treatments is usually enough to end the infestation, but you may repeat this treatment series if you need to. You can also drench the potting mix or soil around a hibiscus with a systemic pest control product. This will kill most of the live thrips that are living in the ground in the juvenile form, and it will speed up control of this pest.


Thrips Scratch Marks on a ‘Voodoo Magic’ Hibiscus Flower

Organic Treatment: If you don’t want to use pesticides, an organic approach is to spray in the same way with any product containing “Neem oil,” a natural product obtained from the Neem tree. It may require more treatments to control thrips, but is a good alternative approach if combined with gathering up all rotten buds and spent flowers so the thrips do not reach the ground around the plant.

A Note to Hibiscus Growers in Florida and the Deep South: A new insect arrived in the USA a few years ago that can also cause bud drop. Called the “hibiscus gall midge,” this tiny fly causes hibiscus buds to turn bright yellow when they are still very small and then fall off the plant. They differ from thrips, which cause large, almost-ready-to-open buds to turn an off-color brownish and fall from the plants. Control of this midge is much the same as for thrips, but it requires a more aggressive treatment program that includes both spraying and soaking the soil around the plants with acephate or imidacloprid (active ingredient) products. If your plants have hibiscus gall midge, contact your local county agriculture department for more info on treatment of hibiscus gall midge in your area.

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Why Are My Hibiscus Buds Falling off?

The most common reason tropical hibiscus buds drop is drying out too much.

Tropical hibiscus (Hibiscus rosa-sinensis) varieties may drop flower buds before they have a chance to open. This usually occurs when the plant is stressed. It can be tricky to diagnose the cause because different conditions can stress the plant. Some of the most common stressors are:

  • Drying out. Tropical hibiscus flower buds will drop off the plant when the plant dries out too much. This often happens as or just after the plant begins to wilt. It’s is the most common cause we see for hibiscus buds falling off.
  • Inconsistent watering. When the plant goes through periods of staying moist, then drying out for a while, then staying moist, then drying out again, the hibiscus buds may drop off. To prevent this, try to keep your plants evenly watered.
  • Sudden environmental changes. You might find your hibiscus drops buds when you first bring it home if your home environment is substantially different than that of the garden center (in terms of light, temperature, watering, etc.). Bud drop usually stops right after your plant gets settled. But other changes — if there’s an especially cold night after a warm day, for example — can also put a little bit of stress on the plant.
  • Heatwaves. Tropical hibiscus love warm, summer temperatures. But some varieties (especially older ones) can suffer when it’s really hot (95F/35C or warmer).
  • Being excessively rootbound. Especially cramped roots can cause hibiscus flowers to drop off. It’s best to repot your plant as it outgrows the pot, particularly if you keep your hibiscus from year to year.
  • Attack from pests. A variety of insect pests, including aphids and thrips, can weaken the plant. This causes buds to drop off before they open into flowers. Hibiscus planted in the ground in warm-winter areas like South Florida may suffer from nematodes. These small, nearly microscopic critters attack the plant roots, and can cause bud drop.

Hibiscus gall midge makes buds fall off

Our hibiscus plants look healthy but keep dropping their flower buds before they open. We have fertilized them but that did not help. Any thoughts?

— Paul Usztok, Palm Coast

The effect of no flowers or bud drop is the classic symptom of the nasty pest, hibiscus gall midge. This midge, Contarinia maculipennis, is a small fly that lays its eggs in hibiscus buds, damaging the buds and making them fall off before they can develop and bloom.

You will need to check your local garden department for an ornamental insecticide that is labeled for hibiscus and follow the label directions carefully for application and safety requirements. You may need to reapply.

Several years ago I planted an orange tree in my yard. It is doing well, growing. However, as it has grown, the higher branches are bearing fruit, which is causing them to sag down. I think it is from the weight of the fruit, but I am not 100 percent sure of that.

Do we need to brace the upper branches to support them? If so, how do you do that?

— William Seitz, Daytona Beach

No bracing is needed on citrus. The limbs are pliable and will sag down. This will probably stimulate branching or water sprouts that grow parallel to the trunk. You can trim those out later after the crop is harvested. Harvest the fruit when it is ripe and you should have no problems.

How can I get rid of Brazilian pepper trees and not hurt the soil? I would like to plant something else there.

— Claudia Smalbein, Daytona Beach

You will need to remove as much as possible of the soil away from the trunk of the tree and outer roots, then cut the entire tree below the soil line. Immediately, paint the trunk with concentrated glyphosate focusing on the outer edges of the trunk which is where the cambium layer (active growing tissue of the tree) is located. Use a disposable foam brush and gloves to help with this procedure. If there are any suckers, you will need to cut them as well and paint them too.

An example would be Ortho Poison Ivy Plus Tough Brush Killer Concentrate. This product will not hurt the soil as it does quickly breakdown. Be sure to follow safety measures as indicated on the label. The trick here it to have the herbicide with you to apply immediately once the cut is made. The tree will suck up the product, which will kill or weaken the tree.

Karen Stauderman is commercial horticulture agent for the University of Florida/Volusia County Extension and host of “Gardeners Hotline” on WDSC-TV Channel 15. Reach her at 3100 E. New York Ave., DeLand, FL 32724-6497, 386-822-5778 or email [email protected]

What Causes Hibiscus Buds to Drop Prematurely?


It’s August, and that means hot, sweltering temperatures. One might think that would be just perfect for certain tropicals like Hibiscus, but one would be wrong. While Hibiscus are tropical by definition, that doesn’t automatically mean they like 100 degree temperatures. Tropical plants by definition, prefer our humidity with temperatures around 88 to 90 degrees. That means that when the thermometer spikes, like it has lately, a myriad of problems ensue for what normally is the “Hibiscus Heaven” Gulf Coast gardens.
Unfortunately, this is a weekly e-mail tip and I don’t have time to detail all the problems that Hibiscus endure because of high temperatures. Luckily, we already covered one of the associated problems with last week’s e-mail tip on Mealy Bugs. In fact, my next book may be all about tropicals for Houston and that would definitely include a major chunk dedicated to Hibiscus. But today, I will answer the question that has been dominating my email of late: “Randy, why do so many of my Hibiscus buds turn yellow and drop before they ever open?”
Like most situations in gardening, there is not one clear cut answer. But there are a couple of dominant reasons, especially in Houston. The first reason for bud drop can be attributed to the really hot weather. Remember, these are tropical plants that would much prefer 88-90 degrees with lots of humidity. Temperatures above 95 for long periods of time can stress out some Hibiscus hybrids to a point that they shed their blooms as a natural defense mechanism.
Moving potted Hibiscus could also cause premature bud drop. Much like the “teenager” of the plant world, the Ficus, which throws a fit by shedding its leaves when you move it, potted Hibiscus plants may also shed buds as a stress indicator.
But the most prevalent reasons that Hibiscus drop their buds are both insect related. While we discussed the onslaught of Mealy Bugs last week, and while they can cause a bit of bud drop, its Thrips and Hibiscus Midges that cause the most “dropped buds.” Interestingly enough, the controls are different, which does not include the home made Mealy Bug control from last week.
So, that means it’s helpful to find out which one is the culprit. Here’s how I do that. First, you have to be convinced it’s not about the extreme temperatures as noted above. Then, you determine if it’s Thrips. The best way to detect Thrips is to take an unopened bud (or one just on the verge of opening, that is starting to turn yellow) and tap it on to a white piece of paper. And if you see tiny little black dandruff-like flecks fall to the paper and they start scampering, then you have Thrips.
Thrips are easy to control, and the best control is any liquid insecticide with Permethrin or Bifenthrin. If you must stay organic, try a liquid Pyrethrum. Spray one of these insecticides all over the remaining blooms. It may need two applications over two weeks, but I’ve often found that one good soaking of the remaining buds is all it takes.
But, if there’s bud drop and there’s no detection of Thrips, and you’re convinced it’s not temperature stress, then just assume away that it’s the Hibiscus Midge, which is hard to detect to the naked eye. Midges come from a technical family of pests called a Gall Midge Fly, which lays it’s eggs in the bud and the microscopic larvae feed on the inside of the bud, causing the premature drop.
Unfortunately, the aforementioned treatment for Thrips and Mealy Bugs will not phase Midges. So, you have to apply a liquid systemic insecticide that is safe for Hibiscus. The systemics need to work their way up through the plant and get to the bud internally since the Midge larvae are so embedded inside the buds. The best control methods for Hibiscus Midges are anything with Acephate, anything with Disyston and anything with Imidicloprid.
There is also one other theory important to keep in mind that might lead to some bud drop, but that almost always leads to an excess of yellowing leaves too. I call it a “lack of consistency.” That would mean a need for consistency in moisture, consistency of food and consistency of sunlight. If all these stay consistent, and if you can prevent the insects talked about earlier, there is little chance of premature bud drop on Hibiscus.
If you like the idea of a Tropical Handbook for Houston Gardening, as my next foray into the publishing world, drop me a line or even suggest a topic or two that you would like to see in such a book.

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