What to Do When Geranium Leaves Turn Yellow? Causes and Solutions
On the windowsills of many homes you can see a kind of flower, and that is the geranium (Pelargonium); especially abroad, it can decorate streets and embellish daily life. Today geraniums are becoming more and more popular in homes, but problems keep cropping up, always the yellowing leaf phenomenon, so what should be done?
Analysis of the causes of geranium leaves turning yellow and how to deal with them:
1. Sudden environmental change causes geranium leaves to turn yellow: old leaves turn yellow due to a change of environment. Many flower lovers, before the high summer temperatures arrive, move their geraniums from an outdoor flower stand indoors, or from a south-facing balcony to a north-facing balcony, or from full-sun outdoors to a corridor, or put up a shade net over the flowers, and so on. A sudden major change in the growing environment will cause the old leaves of the geranium to turn yellow and the flower buds to dry up.
Solution: There is no need to worry too much. The geranium has a process of adapting to the new environment; you only need to pinch off the yellowing large leaves and the dried-up flower buds, and manage everything else as normal.
2. Overwatering causes geranium leaves to turn yellow (water yellowing): because watering is too frequent and too much, the potting soil stays too wet for a long time, and combined with rather high temperatures, part of the geranium's root system rots; this shows on the leaves as the old leaves showing no obvious change while the young leaves turn pale yellow. In severe cases the old leaves will also turn yellow and drop off.
Solution: This requires immediately controlling water, loosening the potting soil and placing it in a ventilated, dry spot to speed up the evaporation of moisture. Or place the flower pot on a stack of newspapers or dry peat, letting the newspapers and peat absorb the excess water in the pot as quickly as possible. In especially serious cases, the whole root ball can be taken out of the pot and placed in dry peat or a soil pile so that the moisture is quickly drawn out, and once the drooping branches and leaves recover, it can be replanted into the pot.
3. Long-term lack of water causes geranium leaves to turn yellow (drought yellowing): some flower lovers may misunderstand the matter of properly controlling water for geraniums in summer, so they let the potting soil dry out completely and wait a long time before watering, causing the geranium leaves to turn yellow and drop from the bottom upward, and in severe cases the leaf stalks droop and appear wilted.
Solution: In this case, the watering method needs to be adjusted, using the principle of alternating dry and wet to water the geranium.
4. Scorching sun causes geranium leaves to turn yellow (sunburn yellowing): write the yellowing symptoms here.
The geranium belongs to a warm and humid environment; being exposed to the scorching sun will cause the leaves to turn yellow and, in severe cases, to die.
Solution: In summer it is best to put it in a cool, shaded place.
5. Dry air causes geranium leaves to turn yellow: dry air and lack of ventilation will cause the branches and leaves to wither and turn yellow.
Solution: Move it to a ventilated place.
6. Insufficient sunlight causes geranium leaves to turn yellow (light-deficiency yellowing): leaves on the inner side of the plant turn yellow and drop due to insufficient light, old leaves turn yellow and wither after new branches and leaves sprout, edema disease and leaf yellowing caused by too much water in hanging plants, as well as major changes in the potted flower's environment (such as suddenly moving it from outdoors to indoors in midsummer, or just after bringing it indoors in winter), and so on.
Solution: Since the yellowing leaves also hope to recover their vitality as soon as possible, they will absorb the nutrients accumulated by the plant itself, consuming more nutrients than they produce. So we do not need to worry too much; we only need to promptly remove the yellow leaves.
7. Too high a temperature causes geranium leaves to turn yellow: this is because the summer temperature is too high, affecting the root system's normal absorption of iron from the soil, causing the newly grown leaves to develop high-temperature, iron-deficiency yellowing and whitening. When iron deficiency is mild, the mesophyll tissue of the young leaves is pale green while the veins remain green; in severe cases the young leaves are entirely yellow-white and develop necrotic spots and gradually scorch and drop off.
Solution: There is no need to worry too much about this case either. You can spray and water with chelated iron solution. Once a week, and after 3 times it can basically return to normal. In addition, lowering the ambient temperature, such as moving it to a ventilated, shaded place or an air-conditioned room, will also let the leaves gradually return to normal.
8. Too low a temperature causes geranium leaves to turn yellow: the geranium likes warm winters and cool summers; indoors in winter, keeping 10-15°C during the day and above 8°C at night will let it flower normally. But the optimum temperature is 15-20°C. If the temperature is too low, it will cause the leaves to turn yellow.
Solution: In winter it is best to keep it indoors and maintain the optimum temperature.
9. Too much fertilizer on geraniums causes leaves to turn yellow (fertilizer yellowing): applying fertilizer too frequently or at too high a concentration will cause root burn and root rot, which shows on the leaves as old leaves turning yellow, and young leaves being thick and fleshy, glossy, and uneven.
Solution: At this point you need to stop fertilizing, do shallow cultivation, and water. In severe cases of fertilizer damage, immediately repot, remove part of the old soil, and wash and rinse the soil ball with water, replace it with plain soil containing no fertilizer, and let it re-root.
10. Long-term lack of fertilizer causes geranium leaves to turn yellow (fertilizer-deficiency yellowing): geraniums bloom diligently, and blooming consumes a large amount of nutrients. Spring is the peak flowering season for geraniums; they bloom with all their might, bringing flower lovers much joy and delight. If we do not apply appropriate topdressing in time, yellow leaves will appear after flowering.
Solution: In this case, first use a weak solution and then gradually increase the fertilizer concentration for topdressing, to prevent a single excessive application from burning the seedlings, until the leaf color returns to normal, then fertilize as usual.
11. Root rot causes geranium leaves to turn yellow: overwatering causes the geranium's roots to rot.
Solution: Remove the rotten roots, sprinkle carbendazim on the roots, plant in new soil, and 3 hours after planting water with carbendazim diluted in water and spray the leaves with carbendazim.
12. Pests and diseases cause geranium leaves to turn yellow: if geraniums are infected by fungi, viruses and other pathogens, they will develop various leaf spot diseases and gray mold, causing localized tissue necrosis in the leaves, appearing as chlorotic yellow spots or yellow-green mottled patches, or the whole leaf turning yellow and dropping. When harmed by pests such as red spider mites and whitefly, the chlorophyll is destroyed, and the leaves also develop small yellow-white spots, or the leaf color turns yellow and drops.
Solution: This requires timely spraying for prevention and control according to the cause of the pests or diseases.
How to grow geraniums:
1. Soil: geraniums are also highly adaptable and can grow in all kinds of soil, but grow best in sandy loam rich in humus.
2. Watering: geraniums like dryness and dislike dampness, so in winter they should not be watered too much; water when the soil is dry and stop when it is wet. When the soil is wet the stems are soft and tender, which is unfavorable for the sprouting and opening of flower branches. Long-term excessive wetness will cause the plant to grow leggy, the flower branches to be borne higher up, and the leaves to gradually turn yellow and drop.
3. Sunlight: geraniums need plenty of sunlight during the growing period, so in winter they must be placed in a sunny spot. With insufficient light, the stems and leaves grow leggy, the flower stalks are thin and soft, and the inflorescences develop poorly. Flower buds under weak light often fail to open well and wither prematurely.
4. Temperature: geraniums like warm winters and cool summers; indoors in winter, keeping 10—15°C during the day and above 8°C at night will let them flower normally. But the optimum temperature is 15-20°C.
5. Fertilizing: geraniums do not like heavy fertilizer; too much fertilizer will make the geranium grow too vigorously and be unfavorable for flowering. To make flowering abundant, water with a dilute fertilizer solution (decomposed soybean cake water) once every 1—2 weeks, and apply 800 times diluted potassium dihydrogen phosphate solution every 7-10 days to promote normal flowering.
6. Pests: when geraniums have poor ventilation and are too damp, they are prone to leaf spot disease and flower wilt disease. After discovery, pay attention to ventilation, immediately remove the diseased flowers and leaves to prevent infection, and spray an equal-amount Bordeaux mixture for prevention and control. The main pests are red spider mites and whiteflies, which harm the leaves and flower branches; they can be killed by spraying 40% omethoate emulsifiable concentrate at 1000 times dilution.
7. Pruning: pruning branches and pinching out tips. To encourage a geranium with more branches to bloom more, the plant should be pinched out several times to promote more branching and bud formation. After the flowers fade, promptly cut off the spent flowers and cut out overly dense and thin, weak branches so as to avoid excessive nutrient consumption, but in winter when the weather is cold, heavy pruning is not advisable.
Geranium winter care
Control temperature and preserve light. Geraniums like warmth and fear cold; in winter, cold-protection measures should be taken, and the indoor temperature should be kept at 15°C-20°C, and at night it must not be lower than 10°C. In an environment where the temperature is too low, the plant grows weakly, which is unfavorable for flower bud differentiation, leading to fewer flowers or even no flowers. But an environment with a temperature above 25°C is also unfavorable for its growth and development. Usually, place the potted plant by a sunny window so it receives sufficient light. If the light is insufficient, the plant tends to grow wildly, affecting flower bud formation and even causing already-formed flower buds to wither.
Moderate water and fertilizer. Geraniums fear dampness and tolerate drought; daily watering should be moderate, generally once every 5-7 days, keeping the potting soil on the dry side and slightly moist. Too much watering will cause the leaves to turn yellow and drop, affecting flowering and even causing root rot and death. Usually spray the leaf surface with clean water regularly to keep the leaves clean, which is favorable for photosynthesis. To make geraniums bloom continuously after the beginning of winter, sufficient nutrients need to be supplied; apply a dilute liquid fertilizer once about every 10 days, which can be prepared by mixing soybean cake, hoof parings and fishy water, and used with added water after fermentation.
Pruning branches and pinching out tips. To encourage a geranium with more branches to bloom more, the plant should be pinched out several times to promote more branching and bud formation. After the flowers fade, promptly cut off the spent flowers and cut out overly dense and thin, weak branches so as to avoid excessive nutrient consumption, but in winter when the weather is cold, heavy pruning is not advisable.
Prevention and control of the main geranium diseases:
1. Leaf spot disease. In the early stage, pinhead-sized, round or irregular brown small spots appear on the leaves, which later gradually expand into dark brown or reddish-brown lesions; in severe cases the entire leaf is covered with lesions until it dries up and drops. The stem and branches also turn black, shrink and rot, and even the leaves on the stem wither and necrose, leaving only a few leaves at the top.
Preventive measures:
a. When cultivating in a greenhouse, do not plant too densely, and pay attention to frequent ventilation and light transmission.
b. When watering, avoid pouring onto the plant and avoid splashing water droplets.
c. Avoid taking cuttings from diseased plants; if diseased leaves and branches are found, promptly cut them off and burn them.
d. During periods of high temperature and humidity, spray 200 times diluted equal-amount Bordeaux mixture once every 2 weeks, for 3 consecutive times.
2. Gray mold. This disease is mainly caused by overwatering, and is even more severe when cold, damp weather occurs. It first harms the flowers, making the edges of the petals darken and wither; when the air humidity is too high, a gray mold layer appears, the small flowers twist together, and the affected petals falling onto the leaves will also cause the leaves to develop the disease. Water-soaked brown lesions appear on the leaf surface, which shrink after drying and are covered with a light gray mold layer.
Control measures: a. Promptly remove diseased leaves and flowers, avoid getting water on the plant when watering, promptly clear the moisture on the leaves and flowers, and always pay attention to ventilation and light transmission.
b. In the early stage of the disease, promptly spray 75% chlorothalonil at 500 times dilution, for 3 consecutive times.