Hibiscus plants are tropical, ornamental shrubs that are grown for their attractive flowers and striking foliage. Currently, there are nearly 300 different species of hibiscus in the world. A common problem they all face is yellowing leaves, which ultimately decreases their aesthetic value.
Hibiscus leaves turning yellow due to drought stress, watering problems, nutrition deficiency, phosphorus in the soil, too high or too low soil pH levels, temperature, low light conditions, plant location, or pest infestation.
To know more about why these problems happen and how to get rid of them, this article will provide you with the information you need.
What Are Hibiscus Plants?
Hibiscus is a genus that consists of nearly 300 species of annuals, perennials, trees, and shrubs that are native to warm, tropical areas. They are grown for their ornamental value due to their attractive, exotic-looking flowers, which are usually short-lived as they bloom for only a day. They can be added to summer gardens or serve as houseplants.
These plants grow best in organically-rich, well-drained soil with at least 4 to 5 hours of bright, direct sunlight when planted indoors and optimum temperatures of 65°F to 75°F. Hibiscus plants are not hard to frost or changes in humidity and temperatures.
Why Are My Hibiscus Leaves Turning Yellow?
Drought Stress
Although hibiscus plants are slightly drought tolerant, they are still susceptible to drought stress, which can negatively affect their water content, water-use efficiency, and photosynthetic abilities. It can also cause wilting and a reduction in growth and blooms during the spring season.
How to Save the Hibiscus Leaves?
- Provide additional irrigation during the driest or hottest months of the year or, in other words, during the summer season.
- When watering, it should be fed directly to the plant’s root system and not on the foliage to avoid foliar disease. For plants in containers, thoroughly water them until water seeps through the bottom of the pot. If there is a saucer below the pot, remove the collected water to prevent fungus problems.
- You can also try adding potassium into the soil to help the plant cope with the stressful conditions brought upon by extreme heat.
Watering Problems
When hibiscus leaves receive too little or too much water, they can experience water stress which can cause the yellowing or dropping off of leaves and buds. Excess water can also cause root and crown rot, while inadequate water can cause drought stress. If symptoms persist, scorch and eventually plant death can occur.
How to Save the Hibiscus Leaves?
- If the hibiscus is overwatered, remove the plant from its soil and dispose of any severely damaged roots. If it is planted in a container, repot them in a new, dry container with potting mix and place them in a warm and sunny location until they have recovered.
- If the hibiscus is underwatered, the simplest solution is to feed it water but in doses so that it doesn’t get overwhelmed. Thoroughly water a 2-inch depth into the soil and work on a schedule to maintain that level.
Nutrient Deficiency
Deficiencies in magnesium, phosphorus, nitrogen, boron, iron, or potassium can negatively affect the plant’s performance, as well as its aesthetic value since it causes yellowing leaves and a light green or wine-red overall coloration. Its growth rate will also sharply reduce, and blotches will start appearing. In worse cases, the plant may never recover.
How to Save the Hibiscus Leaves?
- Moisten up the soil so that the roots can effectively absorb and transport nutrients to the rest of the plant. In some cases, proper watering strategies can fix nutrient deficiency issues.
- Determine what nutrient the soil is missing by performing a soil test. After discerning the cause of the problem, apply a fertilizer that contains the missing nutrient. For example, if the plant needs more nitrogen, purchase fertilizers that have urea, ammonium, nitrate, or manures in the ingredients list.
Phosphorus in Soil
An excess of phosphorus in hibiscus plants can cause stunted growth and even death since the mineral significantly reduces the plant’s ability to absorb micronutrients, specifically zinc and iron. This may be due to the overuse of organic fertilizers. A common symptom would be yellowing between leaf veins or bleaching of leaf tissue.
How to Save the Hibiscus Leaves?
- Spray a solution of 0.5% to 1% of both iron and zinc on plant tissue and leaves to the point of runoff. This is commercially available at garden and lawn centers. Apply every 1 to 4 weeks at the first signs of iron and zinc deficiencies.
- Use mulches or composts and manures that are low in phosphorus from now on, such as blood meal or pine bark mulch.
Too High/Low Soil pH
Too high soil pH can make the plants unable to absorb enough micronutrients, which can result in deficiencies, while too low levels will cause the plant to absorb too much, resulting in micronutrient toxicity. These can be seen in the chlorotic growth on young leaves, which will later turn necrotic (brown then death).
How to Save the Hibiscus Leaves?
- Conduct a pH test on your soil to determine if it has too high or too low pH levels.
- To make the plant soil less acidic, apply materials that contain lime, such as agricultural limestone, which can be in granular, pulverized, hydrated, or pelletized form. You can also use wood ashes, but you would have to use them repeatedly for the best results.
- To increase soil acidity, apply aluminum sulfate or sulfur to the soil. Avoid making contact with leaves, or else leaf burn may occur.
Temperature
Tropical hibiscus is native to warmer regions, which is why they are not tolerant to cold temperatures below 40°F, as this will damage leaf tissue and tender new shoots by turning them limp, dry, and brown. Increased temperatures, on the other hand, will cause heat or drought stress, as mentioned above.
How to Save the Hibiscus Leaves?
- For cold temperatures, cover the plants using hoop houses, cold frames, or hot-cap storage devices. When hibiscus are grown in containers, move them indoors temporarily until the dangers of frost have passed.
- If the hibiscus has been killed to the ground, there is still a possibility of it coming back. Simply cut the plant and leave about 6 inches of growth above the ground and wait for 3 to 4 months for the plant to produce new growth.
- For hot temperatures, refer to the care guide mentioned above.
Low Light Conditions
Hibiscus plants require full sun exposure of at least 4 hours a day but can tolerate a limited amount of shade. However, plants that are consistently placed in shady locations will grow tall and leggy, have the less blooming capacity, and will produce yellow leaves. In the long run, the plant will experience leaf drop if left untreated.
How to Save the Hibiscus Leaves?
- Move the entire plant to an area that receives more direct sunlight, preferably outdoors. When grown indoors, move near south or southwest-facing windows and allow the plant to receive a better quality of indirect or curtain-filtered light.
- If your house lacks natural sunlight, you can use artificial lighting such as fluorescent and LED bulbs, as well as high-pressure sodium and incandescent bulbs.
Location
The environmental conditions of the location the hibiscus plant is grown in are essential for its growth and survival, which is why you should be extra wary of where you plan to grow your hibiscus plants. Failure to comply with their requirements can cause stunted growth, less blooming capacity, and leaf disorders.
How to Save the Hibiscus Leaves?
The only way to save the hibiscus plant is to replant it in a better location. Here are the ways you can do so:
- Choose well-drained, slightly acidic soil. Add decomposed organic matter if you plan to transfer it to sandy soils or use raised beds when planting in heavy clay soils.
- Make sure the plant receives full sun and some light shade. If grown indoors and then transplanted outdoors, allow it to adjust gradually to the new lighting conditions.
- Apply nitrogen and low-phosphorus fertilizer at the time of planting to encourage growth. Water directly to the root system and keep the foliage as dry as possible.
Pest Infestation
Common pests found on hibiscus plants are Japanese beetles, thrips, aphids, borers, scales, bud weevils, mealybugs, and galls. They can cause the leaves to acquire one or a combination of the following: skeletonized appearance, off-colored or yellowing foliage, sooty mold, holes, and leaf drop.
How to Save the Hibiscus Leaves?
1. Non-chemical Control
- If the infestation is low, dispose of any infested parts of the plant, then handpick the pests. You can also use an alcohol-dipped cotton swab to wipe them off or spray them with water.
- If the plant has been severely damaged, discard the plant.
2. Chemical Control
- Use an insecticidal soap for low infestations and stronger pesticides for more serious infestations. Follow the label provided by the manufacturer to effectively get rid of the pests on the hibiscus plants.
List of Sources
Tropical Hibiscus (Hibiscus Rosa-Sinensis)
Guide to Symptoms of Plant Nutrient Deficiencies