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

Gardenia, also known as Huangzhizi, Shanzhi, etc., has bright green foliage, stays evergreen all year round, bears large pure white flowers with a rich fragrance, and has a certain tolerance for shade and resistance to toxic gases, so it is a good material for greening, beautifying and scenting, 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. Temperature too low: 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 the gardenia's roots are damaged, they cannot provide enough nutrients to the plant, and the leaves 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 watering should soak through. When the climate is relatively humid, watering should be restrained.

2. Temperature management: In summer, gardenia should be kept in a well-ventilated, open woodland or shade shed with high air humidity and filtered light; in winter, place it in an environment with sunlight and a temperature not lower than 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, mix 1 gram of laundry detergent with 120 ml of water and add a few drops of peanut oil, stir well and spray, or dip a brush in the mixture and brush them off.

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

How to Grow Gardenia Well?

1. Potting soil: Gardenia is an indicator plant for acid-loving soil, with a suitable pH of 5 to 6. For the growing medium, you can choose leaf mold, peat soil, or composted sawdust plus half garden soil. Do not use old wall soil or coal cinder; using 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 pale, soaking it through at one time. But after the flower buds appear, watering should not be excessive, so as to avoid bud drop.

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

4. Light: Gardenia likes light. It can also grow in half shade for a long time, but the flowering branches will be longer and the flowers fewer. Except for the need for shade during the 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 flowering each year, prune gardenia lightly, cutting off inner branches and diseased or weak branches, and shortening individual leggy branches. But remember that gardenia must not be cut back at the branch tips in spring, otherwise it will not bloom that year.

6. Repotting: It is better to change the soil for gardenia in March of 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 it thoroughly, and place it in a warm, half-shaded place. When new buds begin to sprout, keep it in sunlight.

7. Overwintering: Gardenia can overwinter outdoors in the Qinling area of China, but potted gardenia roots will be damaged after a severe winter. You can place the potted plant in a cold room at around 5°C to let it go dormant, protect the roots well, and keep it in a windproof, sunny place for the winter, so it recovers quickly and blooms early in spring.