Hibiscus leaves turn yellow as a sign of stress due to drought, over watering, a deficit of nutrients or as a reaction to too much phosphorous in the soil. The leaves of tropical varieties of hibiscus turn yellow in response to a sudden drop in temperature.
Keep reading to find out why your hibiscus leaves have turned yellow and how to revive it…
Drought Stress Causes Hibiscus Leaves to Turn Yellow
Yellow leaves on your hibiscus can be a reaction to both stress from too much moisture around the roots or drought stress because of dry soil.
However if the cause of yellow leaves on your hibiscus is due to drought stress, this can distinguished from over watering if the leaves are noticeably shriveled and curling downwards as this is an adaptation to prevent water loss.
Whereas yellow hibiscus leaves caused by over watering tend to droop rather have a shriveled appearance.
Drought stress does is not necessarily always caused by under watering but can also be caused:
- Excess wind. Hibiscus that are planted in excessively windy areas can be more prone to drought stress as hibiscus are native to tropical climates and prefer some humidity rather then excessive wind which saps moisture from the leaves causing them to turn yellow and shrivel.
- Soils drain too quickly. Hibiscus are accustomed to growing is soils that retain moisture (yet allow excess water to drain away from the roots). If the soil in which your hibiscus is planted is sandy or stony then the soil can drain too quickly for the roots to draw up moisture, creating a deficit of moisture and leaves turn yellow as a sign of stress.
- Under watering. Established hibiscuses that are planted in moisture retaining soil with lots of organic content (compost) does not often require watering. However the soil should be kept consistently moist to prevent the leaves turning yellow, therefore hibiscuses often require more water according to how quickly your soil dries out.
Revive Yellow Hibiscus Leaves due to Drought Stress
To revive your hibiscus suffering from drought stress, the first thing you should is…
- Give the hibiscus a generous soak. One generous soak per week is preferable to a little and often watering approach as a soaking ensures the water infiltrates the soil to the depth which it is required to reach the roots. It also encourages the roots to grow and establish which further increases the hibiscus tolerance to drought,
- Shelter the hibiscus from excess winds which sap the leaves of moisture. High winds reduce humidity in the air which is contrary to the preferred growing conditions of the hibiscus as they are native to the tropics. Consider planting some other shrubs to acts as a wind buffer or move your potted hibiscus to an area that is still sunny but is perhaps shelter by a garden fence.
- Add a layer of mulch to the surface of the soil for your hibiscus to retain moisture, add nutrients and improve soil structure. Applying a 1 inch layer of compost, leaf mold or well rotted manure to the soil surrounding the hibiscus improves the soils moisture retain capacity to mitigate the risk of drought. Apply the mulch once in the Spring and then again in the middle of Summer if you have soil that tends to dry too quickly.
- Water the hibiscus as often as required to keep the soil moist. Hibiscus thrives in well draining, yet consistently moist soil and turns yellow when the soil dries. Typically watering once per week with a good soak is good enough to prevent drought stress and yellow leaves but increase the frequency of your watering according to you climate as hot and dry climates require more frequent watering to keep the hibiscus looking green.
- Use a sprayer bottle too mist the leaves to increase the humidity and prevent further water loss.
With consistent watering, shelter from winds and applications of mulch the hibiscus should recover from drought stress.
Over the following week the leaves should appear less shriveled or curled and the yellow foliage should start to turn a healthier green color.
Drought stress is one of the major causes of hibiscus not flowering, however there are several reasons for hibiscus not to display blooms which is why I wrote another article for the solution.
Yellow and Drooping Hibiscus Leaves due to Over Watering
Hibiscus leaves can turn yellow from not just under watering but as a result of stress from over watering or more specifically too much water around the roots, which highlights the importance of getting the balance of moisture right for growing hibiscus.
Yellow hibiscus leaves due too much water around the roots can be because:
- Slow draining soils. Soils that are composed of heavy clay, overly compacted or naturally boggy tend to drain too slowly for hibiscus which causes excess water to pool around the roots. Hibiscus requires moist light friable soil such a loam or compost but it does not tolerate boggy saturated soil as this promotes the conditions for fungal disease such as root rot which can turn the leaves yellow.
- Over watering. Whilst hibiscus do appreciate regular watering so that the soils stay moist, watering every day can create boggy conditions which causes the leaves to turn yellow and droop as a sign of stress.
If your hibiscus is planted in particularly slow draining soil or a boggy low lying area of the garden, then I recommend transplanting it to an area that that has been amended with lots of compost to improve soil structure or grow hibiscus in pots, containers and raised beds as they have more favorable drainage conditions.
It should be noted that it’s also far easier to create a well draining potting mix to suit hibiscus then it is to amend garden soil that is naturally boggy.
Hibiscus in pots can also turn yellow if the pots do not have drainage holes in the base as this emulates the conditions of slow draining soils…
Potted Hibiscus Leaves Turning Yellow
Potted Hibiscus leaves can turn yellow for the same reasons as any other hibiscus turn yellow but there are a few problems unique to pots that can be the cause of yellowing leaves:
- The most common cause for potted hibiscus turning yellow is a lack of drainage. It is essential that your pot has drainage holes in the base or excess water pools around the roots of the hibiscus causing root rot and turning the leaves yellow. Hibiscus roots that have been in the same pot for a long time can become pot bound and a matted lattice of roots can block the drainage hole slowing the drainage depriving the roots of oxygen prevent root respiration which results in yellow leaves.
- If the hibiscus has been in the same pot for a long time the roots can exhaust the soil of nutrients, which can turn the leaves yellow because of a nutrient deficit.
- If the potted hibiscus is indoors then yellow leaves may be a reaction to a lack of light. Hibiscus do not necessarily make the best indoor plant as they prefer full sun and respond to seasonal variations in temperature and light but if you are growing hibiscus indoors locate it in the sunniest window in the house with as much direct light as possible.
- Moving the pot from one area to another can turn the leaves yellow due to transplant shock. Hibiscus can become acclimated to quite a precise location (in terms of sunlight, heat and airflow) and if you move the pot from one area to another or move the pot indoors then the contrast in conditions can turn the hibiscus leaves yellow due to stress.
How to Revive Potted Hibiscus with Yellow Leaves
- Hibiscus are occasional sold in decorative pots without drainage holes in the base from commercial garden centers. Transfer your hibiscus to a similar size pot or bigger with drainage holes in the base as soon as possible and cut back on watering if the soil feels saturated rather then just moist. Allow the soil to dry out before watering again to give your hibiscus a chance to recover from water stress. However if the roots have been in saturated soil for a long time then root rot is likely the cause of the yellow leaves and the plant is difficult to save.
- Refresh the soil for hibiscus that have been in pots for several years to provide more nutrients. Ideally choose a pot that is one size up from the previous pot as larger pots have more capacity for soil and therefore more nutrients. Apply soil half strength multi purpose fertilizer once a month in the Spring and Summer and the yellow leaves should green up.
- Always locate your hibiscus in a location with the most direct sun possible. Hibiscus are native to the tropics and flower to their best in full sun. With more light the leaves can recover from their yellow appearance.
- Hibiscus can take time to adjust to a new location if they have been moved. As long as the hibiscus is in full sun, with well draining yet moist nutrient rich soil and protection for excessive wind the hibiscus should acclimatize to its new surroundings and recover from its yellow appearance, although the display of flowers can be affected.
(If your potted hibiscus is dying, read my article, how to revive a dying hibiscus).
Nutrient Deficient soil Can Causes Hibiscus Leaves to Turn Yellow
Hibiscus leaves can turn yellow as a reaction to a deficit of nutrients in the soil.
Hibiscus are relatively heavy feeders so they often show signs of stress due to a nutrient deficit with the most noticeable being yellow leaves and a lack of flowers.
Sandy or stony soils tend not to retain much nutrients and soil that has not been mulched with any organic matter can also be low in fertility.
Hibiscus thrive in soil that is amended with organic matter (such as compost, leaf mold and well rotted manure) as this provides the ideal conditions in terms of nutrients, soil structure and moisture retaining character.
If your hibiscus has poor growth, yellow leaves and no flowers then follow the steps:
- Apply a 1 inch layer around the soil surrounding your hibiscus twice a year in the Spring and Summer with material such as compost, leaf mold and well rotted manure being ideal. This add nutrients to the soil and stimulates the soils ecosystem which helps to make nutrients more available at the roots of your hibiscus.
- Apply a half strength all purpose liquid fertilizer to the hibiscus once a month during the Spring and Summer to account for the deficit of nutrients in the soil.
It is important to get the balance of nutrients right when it comes to fertilizing hibiscus as too much fertilizer can stimulate foliage growth at the expense of flowers and too much phosphorous can also be a cause of leaves turning yellow which emphasizes the importance of an evenly balanced fertilizer with equal parts Nitrogen, Phosphorous and Potassium (NPK).
Use a granular fertilizer from any reputable brand such as miracle-gro which is widely available from garden centers and from amazon.
(For more tips on promoting flowering, read my article, how to increase hibiscus blooms).
Build up of Phosphorous in Soil Turns Hibiscus Leaves Yellow
Hibiscus are relatively unusual in that they are particularly sensitive to high levels of phosphorous the soil.
When phosphorous builds up in the soil it can prevent the hibiscus roots up-taking other nutrients causing a nutrient deficient that cannot be fixed with more fertilizer.
This can cause the leaves to turn yellow, prevent the hibiscus from flowering in the Summer and cause the plant to die back.
Accumulation of phosphorous in the soil is usually to due to overzealous applications of fertilizer, particularly any fertilizer that contains a disproportionate amount of phosphorous which are often marketed as ‘bloom boosters’.
Scale back the use of any fertilizer if you suspect phosphorous is the cause for your hibiscus leaves turning yellow and water it regularly.
To check definitively whether phosphorous is the cause then it is important to send a sample of your soil off to be tested which is a service available for reputable garden centers and nurseries.
The hibiscus may recover, however if there is a significant build of phosphorous then it is difficult to revive the plant.
Soil pH Prevents Uptake of Nutrients Causing Yellow Leaves
Hibiscus grow well in soils that are slightly acidic between pH 6-7. If hibiscus is planted in soil that is too acidic or too alkaline the this prevents the uptake of nutrients from the soil and the leaves turn yellow with green veins (chlorosis).
Fortunately most garden soil is in the range of pH 6-7 as most organic matter is around this level of slightly acidic pH once full decomposed.
However soil can be overly acidic or alkaline for environmental reasons such as the underlying rock.
If several plants also exhibit yellowing with green veins then I recommend purchasing a soil gauge from amazon or a garden center to establish the pH of your soil.
If your soils is significantly out of the range of pH 6-7 then you should grow hibiscus in pots, containers or raised beds rather then garden soil as changing the soil pH is a tricky process.
If at all possible transplant your hibiscus to a pot with multipurpose compost as this provides the right pH level for your hibiscus as long term hibiscus does not survive in overly acidic or alkaline soils without being transferred to more suitable soil.
Lack of Light Can Cause Yellow Hibiscus Leaves
Hibiscus are native to tropical regions of Asia and thrive and flower to their potential in full sun.
If they are in too much shade then this can cause the hibiscus leaves to turn yellow as well as poor overall growth and fewer blooms as this is contrary to their preferred conditions in their native range.
Locate your hibiscus in the sunniest part of your garden. For established hibiscuses, cut back any vegetation that may be casting shade on the plant or any tree limbs to allow for more light.
Move potted hibsiucs to a sunny patio and ensure any indoor hibsicus are in the sunniest window in your hluuse to preevent yellow leaves.
With more sun the hibiscus should recover from its yellow appearance.
Cold Weather Causes Tropical Hibiscus Leaves to Turn Yellow
There are two species of hibiscus commonly grow by gardeners.
- Tropical hibiscus (Hibiscus rosa-sinensis).
- Hardy hibiscus (Hibiscus spp.).
As you would expect the tropical is much more sensitive to the cold whereas the hardy species can tolerate cold weather and live in a far wider variety of climates.
The tropical hibiscus leaves can turn yellow if the temperature drops suddenly from its normal range. Tropical hibiscus cannot tolerate frost and are hardy in USDA zones 9-11.
Therefore it is important to grow a species of hibiscus that its suitable for your climate to avoid yellow leaves.
Tropical hibiscus can also drop their yellow leaves after serious cold shock but can recover if the temperatures stay mild.
Outside of tropical climates the tropical species of hibiscus struggle to survive.
Hardy hibiscus varieties can tolerate frost but should be grown in areas of full sun and notably flower for longer then tropical varieties.
Insect Pests can Cause Hibiscus Leaves to Turn Yellow
The healthier your hibiscus is the more resilient it is to pests and disease.
If your hibiscus is under stress due to lack of light, adverse soil conditions etc. then it is more vulnerable to insect infestation.
Whilst there are several insects that can affect hibiscus the most likely candidate for turning hibiscus leaves yellow is the spider mite.
Spider mites cause yellow pin sized spots on your hibiscus, potentially cause in the leaves to drop and fewer flowers on display.
Spider mite infestations however are rarely lethal and can be easily treated.
Spider mites are more common in environments with lower humidity, therefore spraying your hibiscus leaves with mist can be a good disincentive.
For more serious infestations use a insecticide spray derived from neem oil is an effective treatment and is non toxic to other wildlife. It may take two or three treatments to address the spider mite problem. The affected yellow leaves often drop off but the hibiscus should recover.
Insecticides sprays are available for garden centers and amazon.
- The reason hibiscus leaves turn yellow is because of drought stress, over watering, too much nitrogen or too much phosphorous in the soil. Sudden temperature change can cause hibiscus leaves to turn yellow as can a lack of direct sun.
- Drought stress due to sandy soils, excess wind and under watering can cause hibiscus leaves to turn yellow, shrivel up and drop off. Revive the hibiscus by watering more regularly, applying mulch and spray the leaves with a mist sprayer.
- Hibiscus require full sun to grow well and stay healthy. Too much shade causes hibiscuses to turn yellow, drop leaves and display fewer flowers.
- To revive hibiscus, recreate the conditions in which they thrive in their native habitat with full sun, lots of moisture, good drainage and nutrient rich soil.