Why Gardenia Leaves Turn Yellow and How to Fix It with Proper Care
Gardenia leaves stay evergreen through all four seasons, and its flowers are fragrant and elegantly understated, with green leaves and white blooms that look especially fresh and lovely. It works well planted in front of steps, beside ponds and along roadsides, and can also be grown as a hedge or in pots for ornamental display; the flowers can additionally be used in cut arrangements and worn as decoration. Gardenia is a popular potted plant, and many people like to grow a pot of it at home, but before long they notice the gardenia leaves turning yellow, so what is going on when gardenia leaves turn yellow? What should you do? How should you care for it?
1. Causes of yellowing gardenia leaves
1. Improper watering
If the usual watering is not enough, it may cause yellow leaves. In addition, during cultivation you should not water too much either; standing water in the pot or overly wet potting soil will cause the young leaves to become dull and lusterless and to grow slowly, while the old leaves turn yellow-green and gradually wither.
2. Improper light
Light that is too strong or too weak will both cause the plant's leaves to turn yellow. With prolonged direct strong light, yellow patches appear on the leaf surface, but if the plant is kept in a shaded environment for a long time, the leaves drop because they cannot get enough sunlight, so light must be supplied in time.
3. Improper fertilizing
During gardenia cultivation, a fertilizer concentration that is too high will cause the plant to turn yellow: the leaf tips of new leaves take on a yellow-brown color, the leaf surface becomes uneven and lusterless, and the old leaves gradually wither and drop. At this point fertilizer needs to be replenished in time, but before that you need to judge from the plant's symptoms which nutrients should be added, as follows:
Nitrogen deficiency: with nitrogen deficiency the leaves simply turn yellow, and the new leaves are small and brittle.
Potassium deficiency: when the plant lacks potassium, the 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: the yellowing starts on the old leaves and gradually spreads to the new leaves, while the veins still remain green; in severe cases the leaves drop and the plant dies. ⑤ Phosphorus deficiency: the old leaves turn purplish red or dark red.
4. Temperature too low
Gardenia can tolerate low temperatures, but temperatures that are too low will cause the leaves to yellow. During gardenia care, winter cold injury is common; if no warming measures are taken on early spring and early winter nights, the plant is easily damaged by cold.
2. How to deal with yellowing gardenia leaves
1. Let it adapt to the environment gradually
A gardenia just bought from the market has mostly been taken out of a greenhouse, and moving it to a new environment requires a period of adjustment. If the environmental difference is too great, it will cause yellow leaves, and this is an uncontrollable factor. So when the leaves turn yellow, first observe for a period of time and care for it well during that time.
2. Water sensibly
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 substance, such as edible vinegar or citric acid.
4. Open the windows for ventilation
Gardenias cared for indoors need frequent ventilation; make sure the environment is bright, and place the plant near a window for care.
5. Fertilize sensibly
Supplement fertilizer appropriately according to the plant's growth state, and make sure every nutrient is balanced. If too much fertilizer was applied, immediately water to flush it out, or repot and change the soil.
6. Prune away yellow leaves
The gardenia has woody stems; when yellow leaves appear, directly cut off the branch that has turned yellow, which ensures the main stem grows normally, and with careful care, new leaves will grow before long.
3. 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 not suitable, later care will be very troublesome.
For the growing medium, usually choose leaf mold and peat soil plus half garden soil; do not use coal cinder, or simply 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 on once a week. A complete organic liquid fertilizer can also be used.
At the bud stage, apply a top dressing 1~2 times, watering on a potassium dihydrogen phosphate solution, which can make the flowers larger and fuller and the fragrance rich.
Stop fertilizing when summer temperatures are above 35°C and in autumn above 15°C.
3. Watering
Gardenia likes a moist, humid environment. During the growing period from April to September, keep the potting soil moist, watering so that it dries and then gets wet again, and at night you can mist to wet the leaves and maintain humidity. If the plant is growing too vigorously, do not water at night; water after the sun comes up in the morning.
In northern areas with alkaline water, when watering, let the tap water stand for a day before watering. Every 3~5 days, water on a little citric acid solution, which keeps the leaves emerald green.
4. Light
Gardenia's growth needs plenty of sunlight; if kept in half shade for a long time, the flowering branches become weak and slender. During care, apart from shading needed at midday in July and August and winter dormancy, it can be kept in the sun the rest of the time.
5. Points to note
(1) Pest and disease control. Gardenia is fairly prone to chlorosis, leaf spot disease and scale insects, especially in the flowering summer, when the weather is muggy and humid and fungal infection brings on disease and pests. Once discovered, spray pesticide promptly to disinfect, and isolate it from other plants to avoid contagion.
(2) Soil acidification. Gardenia likes fertilizer but is afraid of strong fertilizer. During the growing season, apply decomposed cake fertilizer water once every half month, at a low concentration, so as not to burn the roots and affect the growth of the flower buds. At the same time, note that the soil needs to be acidified in time. Most household water is alkaline, and long-term watering will make the soil alkaline, so water on a ferrous sulfate solution at the right time to change the soil's acidity and alkalinity, which can promote the plant's growth.
(3) Winter dormancy. Although gardenia is cold-tolerant, a potted gardenia's root system will be damaged after a harsh winter, and it recovers slowly in spring. But if kept 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 in a 5°C environment to let it go dormant, or wrap the flower pot in insulating material and place it outdoors in a sunny, wind-sheltered spot to overwinter.
(4) Prune appropriately. When the gardenia's main stem grows to 20 cm, pinch off the growing tip, leaving 3~4 branches, to encourage branching. After flowering each year, prune lightly and cut off weak and diseased branches. But in spring, gardenia must not be cut back hard at the top of the branches, otherwise it will be hard for it to bloom that year. (Editor's recommendation: How should gardenia be pruned?)
(5) Repot and change the soil at the right time. Gardenia is very vigorous; a small seedling grows from a few centimeters to several tens of centimeters, so it should be repotted according to the plant's size. When the plant's branch length is 2~3 times the diameter of the pot's mouth, it needs repotting. When repotting, prune the 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