Reasons for Yellowing Gardenia Leaves and Care Solutions

Gardenia leaves stay evergreen through all four seasons, and the flowers are fragrant and elegantly simple, with green leaves and white blooms looking especially fresh and lovely. It suits planting in front of steps, beside ponds and along roadsides, and can also be used for hedges and as a potted ornamental; the flowers can also be used in cut arrangements and as wearable decoration. Gardenia is a popular potted plant, and many people like to grow a pot at home, only to soon find that the gardenia leaves turn yellow. So what causes gardenia leaves to turn yellow? What should be done? How should it be cared for?

I. Reasons for Yellowing Gardenia Leaves

1. Improper watering

If the usual watering is insufficient, it may cause yellow leaves. In addition, during cultivation, watering should not be excessive either; standing water in the pot or overly wet potting soil will cause tender leaves to become dull and lusterless and to grow slowly, while old leaves turn yellow-green and gradually wither.

2. Improper lighting

Both too strong and too weak light will cause the plant's leaves to turn yellow. With prolonged direct strong light, yellow spots will appear on the leaf surface, but if placed in a shaded environment for a long time, the leaves will drop because they cannot get enough sunlight, so light should be supplemented in time.

3. Improper fertilizing

During gardenia cultivation, a high fertilizer concentration will cause the plant to turn yellow, the leaf tips of new leaves will appear yellow-brown, the leaf surface will be uneven and lusterless, and old leaves will gradually wither and drop. At this point, fertilizer needs to be supplemented in time, but before that, it is necessary to judge from the plant's symptoms which fertilizers should be supplemented, as follows:

Nitrogen deficiency: with simple nitrogen deficiency, the leaves turn yellow, and new leaves are small and brittle.

Potassium deficiency: when the plant lacks potassium, old leaves change from green to brown.

Iron deficiency: at first the leaves are pale yellow or white while the veins remain green; in severe cases the veins also turn yellow or white, and eventually the leaves dry up and die.

Magnesium deficiency: yellowing starts from the old leaves and gradually spreads to the new leaves, the veins remain green, and in severe cases the leaves drop and the plant dies. ⑤ Phosphorus deficiency: old leaves turn purplish red or dark red.

4. Too low temperature

Gardenia can tolerate low temperatures, but overly low temperatures will cause leaf yellowing. During gardenia care, it is prone to cold injury in winter; if no warming measures are taken at night in early spring and early winter, the plant is easily cold-damaged.

II. How to Handle Yellowing Gardenia Leaves

1. Let it adapt to the environment slowly

Gardenias just bought back from the market have mostly been taken out of greenhouses and need a period of adaptation when moved to a new environment. If the environmental difference is too great, it will cause yellow leaves, which is an uncontrollable factor. Therefore, when the leaves turn yellow, observe for a period first and care for it well during this time.

2. Water reasonably

If it is short of water, replenish it in time; if the usual watering is too much, reduce the frequency and amount of watering.

3. Acidic water is more suitable

Gardenia likes acidic soil, while tap water is alkaline or neutral, so when watering, often add some acidic substances, such as edible vinegar or citric acid.

4. Open windows for ventilation

Gardenias cared for indoors need frequent ventilation; ensure the environment is bright, and place the plant by a window for care.

5. Fertilize reasonably

Supplement fertilizer appropriately according to the plant's growth state to ensure each nutrient is balanced. If too much fertilizer is applied, water immediately to flush it out, or repot and change the soil.

6. Prune yellow leaves

Gardenia has woody stems. When yellow leaves appear, directly cut off the yellowed branches, which can ensure the normal growth of the main stem; with careful care, new leaves will grow before long.

III. How to Care for Gardenia

1. Potting soil

Gardenia likes acidic soil, with a suitable pH of 5 to 6, so prepare suitable soil before planting. If the soil's acidity and alkalinity are unsuitable, later care will be very troublesome.

For cultivation soil, usually choose leaf mold, peat soil plus half garden soil; do not use coal cinder, or directly buy special gardenia soil, which is convenient and practical.

2. Fertilizing

Gardenia likes fertilizer; when planting, add decomposed cake fertilizer to the soil as a base fertilizer.

During the growing season, use cake fertilizer and ferrous sulfate fermented into fertilizer water and water it once a week. A complete-nutrition organic liquid fertilizer can also be used.

At the bud stage, topdress 1~2 times and water with potassium dihydrogen phosphate aqueous solution, which can make the flowers larger and the fragrance richer.

When the summer temperature is above 35°C and the autumn temperature is above 15°C, stop fertilizing.

3. Watering

Gardenia likes a moist, humid environment. During the growing period from April to September, keep the potting soil moist, watering when dry and stopping when wet; at night, mist the leaves to keep them humid. If the plant grows too vigorously, do not water at night; water after the sun comes out in the morning.

In alkaline-water areas of the north, when watering, let tap water stand for a day before using it. Every 3~5 days, water with a little citric acid aqueous solution, which can keep the leaves emerald green.

4. Lighting

Gardenia needs plenty of sunlight to grow; if kept in half shade for a long time, the flowering branches will be weak and slender. During care, except for shading needed at noon in July and August and winter dormancy, it can be cared for in the sun at other times.

5. Precautions

(1) Pest and disease control. Gardenia is relatively prone to chlorosis, leaf spot disease and scale insects, especially in the flowering summer, when the weather is stuffy, hot and humid, and fungal infection induces diseases and pests. Once discovered, spray pesticides in time to disinfect, and isolate it from other plants to avoid contagion.

(2) Soil acidification. Gardenia likes fertilizer but fears strong fertilizer. During the growing season, apply decomposed cake fertilizer water once every half month, and the concentration should be low so as not to burn the roots and affect the growth of flower buds. At the same time, note that the soil should be acidified in time. Most household water is alkaline, and long-term watering will cause the soil to become alkaline; watering with ferrous sulfate solution at the right time to change the soil's acidity and alkalinity can promote the plant's growth.

(3) Winter dormancy. Although gardenia is cold-tolerant, after a harsh winter the root system of potted gardenia will be damaged and recovery in spring will be slower. However, if placed indoors with heating, where the temperature is higher and light is insufficient, the plant's growth slows and it blooms later the next year. The best method is to place the pot at 5°C to let it go dormant, or wrap the flowerpot with insulation material and place it outdoors in a sunny, wind-sheltered spot to overwinter.

(4) Proper pruning. When the main stem of gardenia grows to 20 cm, pinch off the tip, leaving 3~4 branches, to promote branching. After flowering each year, prune lightly, cutting off weak branches and diseased branches. But in spring, gardenia must not be cut back at the branch tips, otherwise it will be difficult for it to bloom that year. (Editor's recommendation: How to prune gardenia?)

(5) Change the potting soil at the right time. Gardenia has strong vitality; a small seedling grows from a few centimeters to several tens of centimeters, so the pot should be changed according to the plant's size. When the length of the plant's branches is 2~3 times the diameter of the flowerpot rim, it needs repotting. When repotting, prune old roots in time, change half the soil, water thoroughly, and place it in half shade for a week; after new buds grow, move it into the sun