Hibiscus does not flower if it is too much shade, stressed due to drought or if it is heavily pruned in late Spring. Too much Nitrogen fertilizer promotes hibiscus foliage growth with fewer flowers and too much Phosphorous also prevents flowering.
Hibiscus flower in the Summer months. If your hibiscus has not flowered, then keep reading to learn why and how to promote flowers on your hibiscus…
1. Too Much Shade Prevent Hibiscus Flowering
The most important condition for hibiscus to flower is the amount of sun it receives per day.
Hibiscus flowers to its full potential when in full sun with abundant fragrant flowers.
If your hibiscus is in a shadier location of your garden then the less energy the plant has for as display of flowers in Summer.
Hibiscus are indigenous to the sunny and humid tropical and subtropical climates in Asia where they flower in full sun and warm weather.
Always locate your hibiscus in an area with 6 or more hours of sun whether they are a variety of the tropical species of hibiscus (Hibiscus rosa-sinensis) or the hardier species of hibiscus (Hibiscus spp.) as both require full sun for flowering (hardier hibiscus can tolerate cooler temperatures).
If your hibiscus is in a shady area of your garden or indoors then the plant is living in conditions that are contrary to its requirements which causes stress and prevents flowering.
If possible cut back any vegetation that is casting shade on your hibiscus or ideally if its potted move it to a sunny patio.
Only the tropical varieties can grow indoors (hibiscus are not necessarily the best houseplants) but ensure that your hibiscus is in the sunniest window of your house to promote blooms.
2. Too Much Phosphorous can Prevent Hibiscus Blooming
Whilst phosphorous is often the key ingredient for ‘bloom boosters’ in fertilizers, they are to the detriment of hibiscus flowering as hibiscus is particularly sensitive to a build of of phosphorous in the soil.
An accumulation of phosphorous in the soil prevents the hibiscus roots from up-taking other essential nutrients which can stop your hibiscus form flowering an even kill the plant.
Avoid any fertilizer that is not well balanced (a well balanced fertilizer has an even ratio of Nitrogen, Phosphorous and Potassium NPK) and avoid any heavy use of fertilizer, prioritizing improving soil fertility with organic mulches (such as well rotted manure).
Hibiscus is unusual in its sensitivity to phosphorous so this can be a frequent cause of the flowers not emerging for gardeners as it is quite a specific problem.
(Too much phosphorous is one of the causes of hibiscus leaves turning yellow however there are several reasons why hibiscus leaves turn yellow so I wrote another article for the solution).
3. Too Much Nitrogen Prevents Hibiscus Flowering
Hibiscus are sensitive to too much phosphorous and even nitrogen when you use fertilizer in too high concentration.
Too much nitrogen causes your hibiscus to grow foliage at the expense of blooms so its important to moderate your applications.
Too much fertilizer can also increase the hibiscus’s vulnerability to pests such as aphids which feed and sap and can cause flower buds to drop so if its infested.
Hibiscus are heavy feeders but as stated the best way to feed them is to add mulch to improve the soil (compost, leaf mold or well rotted manure) an perhaps use a half strength general liquid fertilizer from a brand such as miracle-gro, once a month during the Spring and Summer.
This is often a good balance to provide the hibiscus with the nutrients it requires to display flowers without over indulging the plant and causing it not to flower.
If your hibiscus has no flowers but lots of foliage then scale back the use of fertilizer and water it regularly.
It may not display flowers this year but with a more diligent approach to fertilizing the hibiscus should flower the following year.
4. Pruning at the Wrong Time of Year
Hibiscus flowers on new years growth so pruning in the growing season can have a serious impact on blooms.
A heavy pruning in the early Spring can either cause the hibiscus to not flower in the Summer or to delay flowering significantly.
If flowering is delayed then the flowers are more likely to emerge when the temperature is cooler in the Fall rather then in the height of Summer and often wilt or drop far quicker then they otherwise would.
Hibiscus responds better to a light prune at the end of the growing season after flowering around September/October so new growth can in Spring can support the flowers.
5. Hibiscus in Pots Not Blooming
The same reasons for hibiscus not flowering also apply to potted hibiscus but there are a few conditions that specific to pots that may cause your hibiscus not to flower.
If your potted hibisucs is not blooming this is often because:
- The hibiscus has been in the same pot for many years and exhausted the available nutrients. Pots have a limited capacity for soil and therefore less available nutrients. Potted soil can also become compacted over time and frequent watering washes out water soluble nutrients.
- Small pots dry out too quickly. Hibiscus requires full sun and warm temperatures and consistently moist soil to flower. Smaller pots retain less water and heat up quickly in the soil which increases evaporation and causes drought stress to your hibiscus, even with consistent watering and prevents hibiscus from flowering.
- Pots without drainage holes in the base. Hibiscus require well draining soil, so if they are planted in decorative pots without drainage hole in the base, then water pools around the roots which causes root rot, prevents flowering and the plant can die back as a result.
- In smaller pots the roots can become pot bound and even cause a blockage for the drainage holes of the pot which causes slower drainage, boggy soil and increases the risk of diseases.
If your hibiscus has been growing in the same soil for many years then you should re-pot your hibiscus to promote plant health and flowering.
Re-pot with quality multi purpose compost for good soil structure and moisture retaining capacity.
Re-pot the hibiscus in a larger pot so the roots can establish and access the nutrients and moisture they require for flowering without drying too quickly in the intense Summer sun.
Ensure that the pot or container has drainage holes in the base and place a one inch layer of gravel in the bottom of the pot to ensure good drainage.
(To learn how to save hibiscus, read my article, how to revive dying hibiscus).
6. Climate can Affect Hibiscus Flowering
Hibiscus are native to tropical and sub tropical climates in Asia where they thrive in sunny, humid and warm conditions.
There are two species of hibiscus grown by gardeners:
- Tropical hibiscus (Hibiscus rosa-sinensis)
- Hardy hibiscus (Hibiscus spp.)
Tropical hibiscus require warmer more humid conditions typically and does not tolerate freezing temperatures (hardy in USDA Zones 9-11).
The hardy species can tolerate a wider temperature range and generally flowers for longer the tropical hibiscus although this can depend on the specific variety.
Tropical species are much harder to care for outside of their typical climates and therefore do not flower as readily as they are often stressed if conditions are not to their liking.
The hardy species tends to flower more readily in a greater range of climates and conditions.
If your struggling to get your hibiscus to flower then check what species the variety belongs to and plant the appropriate hibiscus for your climate for improved display of flowering.
7. Hibiscus do Not Flower Due to Drought Stress
Hibiscus are native to the tropics and grow in soil with a high organic content in areas of frequent rainfall.
If your hibiscus is not flowering then this can be because it is stressed due to drought.
Drought stress is typically caused by:
- Under watering. Whilst established hibiscus may not require as much regularly watering, potted and less mature hibiscus shrubs should be watered as frequently as required so that the soil is consistently moist to promote plant health and flowering in the Summer.
- Sandy soil can does not retain enough moisture. If your soil has lots of sand or stone then typically it drains too fast for the roots of your hibiscus to draw up moisture which causes drought stress and can reduce flowering.
To improve your soils capacity for retaining moisture, I recommend giving your hibiscus a good soak with a hose and then apply a layer of mulch to the surface of the soil around your hibiscus.
Materials such as compost, leaf mold and well rotted manure are excellent mulches for hibiscus as they retain moisture, add nutrients and maintain the soils pH to suit your hibiscus.
The mulch also improves the soil structure so apply a layer around your hibiscus plants at the start of Spring.
The frequency of watering depends on your climate and the weather but if you test your soil for moisture to a finger depth regularly you can determine how quickly your soil dries out.
As soon as the soil is dry give your hibiscus a good soak to ensure a healthy plant that displays flowers in Summer.
8. Hibiscus Does Not Flower in Slow Draining Soils
On the other end of the spectrum is hibiscus not flowering if the ground is boggy. Whilst hibiscus requires consistently moist soil it should also be well draining.
If the soil is heavy clay or compacted and water pools around the roots of the hibiscus it can suffer from stress that cause it not to flower and promote the conditions for fungal disease such as root rot which can cause your hibiscus to die back.
If the soil feels overly damp or looks boggy then scale back the watering to give the soil around the roots a chance to dry out.
Hibiscus often does not last long in saturated soils such as heavy clay so you should transplant it to an area of well draining soil or into a pot if it is small enough.
For boggy low lying gardens I recommend growing your hibiscus in pots, containers or raised beds as they have more favorable drainage conditions and you can customize the soil profile so that it is suitable for hibiscus to grow and flower which is far easier then amending boggy garden soil.
9. Pests Can Cause Hibiscus Flower Buds To Fall Off
Hibiscus are usually quite resilient to pests and diseases, but if the hibiscus is under stress for any reason then this can increase the risk of infestations that cause hibiscus flower buds to drop or not open properly.
These casuses of stress are:
- Water stress due to drought or boggy soil.
- Too much fertilizer.
- Nutrient poor soil.
Too much nitrogen from fertilizer in particularly causes more soft and succulent foliage growth which attracts insects such as mealy bugs, aphids, thrips and spider mites.
Inspect the leaves and if you notice any sign of insect pest infestations then use an organic insecticide derived from neem oil (available from garden centers and on Amazon) as neem oil is not toxic to other animals in your garden and can sort out your insect problem.
The spray typically takes 2 or 3 applications to leaves to sort out an infestation. Your hibiscus may not recover in time to flower this year but getting rid of pests keeps your hibiscus healthy and it should flower the following year.
- The reason for hibiscus not flowering is usually because of too much shade, drought stress or too much fertilizer. Nitrogen promotes foliage at the expense of flowers and too much phosphorous reduces hibiscus blooms by immobilizing nutrients in the soil.
- Pruning at the wrong time can prevent flowering as hibiscus flowers on new growth. Avoid pruning in the Spring or Summer. The best time to prune hibiscus for flowering is in the Fall.
- Drought stress or slowing draining soils can prevent hibiscus flowering. Hibiscus requires consistently moist well draining soil to display flowers without stress. Unhealthy plants are less resilient and more likely to be affected by pests or disease.