What to Do When Gardenia Leaves Turn Black? Causes and Solutions

Gardenia is also known as Huang Zhizi, Shan Zhi, etc. Its leaves are bright green and evergreen all year round, its flowers are large and pure white with a rich fragrance, and it also has a certain tolerance for shade and resistance to toxic gases, so it is a good material for greening, beautification and fragrance, and is very suitable for balcony greening, potted flowers, cut flowers or bonsai, etc. Now let us take a look at what to do when gardenia leaves turn black!

Why do gardenia leaves turn black?

1. Overwatering: The reason gardenia leaves turn black may be overwatering, which prevents the roots from breathing and can even cause root rot.

2. Too low temperature: The suitable growth temperature for gardenia is 16-18°C, and the reason the leaves turn black may also be that the temperature is too low.

3. Pests and diseases: The reason gardenia leaves turn black may also be sooty mold caused by aphids, whiteflies, scale insects, etc.

4. Root damage: When gardenia roots are damaged, they cannot provide enough nutrients to the plant, and the leaves will turn black.

What to do when gardenia leaves turn black?

1. Water reasonably: When gardenia leaves turn black, the first thing to consider is the watering problem. The principle of watering is to water only when the potting soil is dry, and each time water thoroughly. When the climate is relatively humid, watering should be restricted.

2. Temperature management: In summer, gardenia should be kept in a well-ventilated, humid, and partially shaded sparse forest or shaded shed. In winter, place it in an environment with sunlight and a temperature not below 0°C to let it go dormant.

3. Pest and disease control

① Aphids: For aphids, crush two garlic cloves into juice, add 1 liter of water, and spray the affected plant.

② Whiteflies: For whiteflies, add 1 gram of laundry detergent to 120 milliliters of water, then add a few drops of peanut oil, mix well and spray, or use a brush dipped in the mixture to brush them off.

③ Scale insects: For scale insects, use a cotton swab dipped in alcohol or soapy water to remove them.

How should gardenia be grown properly?

1. Potting soil: Gardenia is an indicator plant for acid-loving soil, with a suitable pH of 5 to 6. The cultivation soil can be leaf mold, peat soil, or composted sawdust plus half garden soil. Do not use old wall soil or coal cinder. Commercially available clivia soil is more convenient and practical.

2. Watering: Gardenia likes moist soil and relatively high air humidity. During the growing period from April to September, keep the potting soil moist. Usually, water when the potting soil turns white, and water thoroughly each time. However, after the flower buds appear, watering should not be excessive to avoid bud drop.

3. Fertilizing: Gardenia is a fertilizer-loving plant. Add 3% decomposed cake fertilizer to the culture soil as a base fertilizer. During the growing season, apply alum fertilizer water made by composting cake fertilizer with ferrous sulfate once a week. During the bud stage, apply 0.1% potassium dihydrogen phosphate aqueous solution 1 to 2 times, which can make the flowers larger and the fragrance richer.

4. Light: Gardenia likes light and can also grow in partial shade for a long time, but the flowering branches will be longer and the flowers fewer. Except for the need for shade during strong midday light from July to August and during the winter dormancy period, it generally needs to be kept in sunlight to produce abundant flowers and lush leaves.

5. Pruning: After gardenia blooms each year, prune lightly, cutting off inner branches and diseased or weak branches, and shorten individual leggy branches. But remember that gardenia branch tips must not be shortened in spring, otherwise it will not bloom that year.

6. Changing soil: It is better to change the soil for gardenia in March in spring. After taking it out of the pot, cut off some old roots, shake off half of the old soil, plant it in the pot with new soil, water thoroughly, place it in a warm, partially shaded place, and when new buds sprout, place it in sunlight for care.

7. Overwintering: Gardenia can overwinter outdoors in the Qinling area of China, but potted gardenia roots will be damaged after severe winter. The potted plant can be placed in a cold room at around 5°C to go dormant, protecting the root system. Place it in a windproof, sunny place for winter, and it will recover quickly and bloom early in spring.