Chrysanthemum Leaves Turning Yellow and Black and Falling Off? Here's How to Fix It
Influenced by traditional Chinese culture, chrysanthemums have a great many admirers, which has made the chrysanthemum a relatively common plant and also a very widely grown and very typical plant in our country. However, loving chrysanthemums does not mean you can grow them well; growing chrysanthemums requires not only love, but also cultivation techniques and methods.
What to Do When Chrysanthemum Leaves Turn Yellow and Black
1. Alkaline soil: Chrysanthemums prefer fertile, highly permeable, slightly acidic soil. Soil with a pH above 7.5 very easily causes the lower leaves of chrysanthemums to drop off or the leaves of the whole plant to turn yellow.
Solution: Regularly water with fermented rice-washing water or rainwater.
2. Overwatering: Watering too much causes the soil to stay waterlogged and wet for a long time, with poor aeration and even rot of some fibrous roots, which shows up as the young leaves of chrysanthemums turning dull yellow and lusterless, with new shoots shrinking.
Solution: Water chrysanthemums on the principle of watering when the potting soil is dry, not watering when it is not dry, and watering thoroughly when you do water. In summer, when the weather is hot and the potting soil dries easily, water fully, but do not water at noon; water thoroughly in the morning, and if the potting soil is dry at dusk you can water once more. After rain, tip the pot to drain off the water. When watering, prevent mud from splashing onto the leaves.
3. Long-term water shortage: Because chrysanthemums have not been watered thoroughly or have been dehydrated for a long time, although the new leaves keep a normal color, the lower leaves gradually dry, yellow, and fall off from the bottom upward as they age.
Solution: Chrysanthemums need ample watering during the growing period. Once the potting soil is dry, water again, but note that you must not water when the midday sun is strong.
4. Overfertilizing chrysanthemums: Applying too much fertilizer to chrysanthemums burns the roots, which shows up as yellowing leaves.
Solution: Fertilizing chrysanthemums should follow the rule of light fertilizer applied frequently; once flower buds appear, it can be slightly more concentrated. For topdressing, use 2 parts decomposed soybean cake or sesame oil residue plus 8 parts clear water, applied once every 7 to 10 days. After buds appear, use 1 part fertilizer plus 3 parts water, mixed with a small amount of potassium dihydrogen phosphate for topdressing. After applying, promptly rinse the fertilizer solution off the leaves with clear water.
5. Leaf blight disease: Infection by leaf blight is one cause of chrysanthemum leaves turning yellow and withering, mainly harming the flowers and leaves of chrysanthemums.
Solution: Spray once every 15 days with 500 times diluted wettable amobam or zineb.
Solutions for Chrysanthemum Leaf Drop
1. Fertilize reasonably
The chrysanthemum is by nature a fertilizer-loving flower, but its needs differ at different growth stages. Improper fertilization at any of the different stages can also cause the lower leaves of potted chrysanthemums to wither, yellow, and fall off. For potted chrysanthemums planted in spring, the rejuvenation management requires slightly more fertilizer, and nitrogen fertilizer should dominate to encourage new branches and leaves; after summer cuttings are transplanted into pots, the plants are in the stage of growth control, so fertilize little or not at all; in autumn, potted chrysanthemums begin vigorous growth and need a large amount of fertilizer, so phosphorus and potassium fertilizer should be increased, but fertilization must not be excessive, as excess will cause the lower leaves to age and fall off.
2. Water appropriately
After the Start of Autumn, the water requirement of potted chrysanthemums should gradually increase. But at this time, both too much and too little watering will cause the lower old leaves of the potted chrysanthemum plant to wither, yellow, and fall off. Also, be careful that watering or rain does not splash muddy water onto the leaves; it is best to spread a layer of dry grass on the surface of the pot so that the leaves are not soiled when watering or when heavy rain falls, which would cause yellow leaves and leaf drop.
3. Prevent and control pests and diseases
In early autumn, potted chrysanthemums are most susceptible to diseases and insect pests. The main diseases include black spot, which harms the basal leaves at the lower part of the plant and causes them to fall off; and powdery mildew, which makes the affected leaves bear white powdery lesions that spread from dots into lines, affecting the appearance of the leaves and also causing leaf drop. For diseases, before chrysanthemums become diseased, prevention should be carried out early, spraying 2 to 3 times a month with 0.1% Bordeaux mixture of equal amounts or 50% zineb at 1000-1500 times dilution. Insect pests include aphids, red spider mites, green caterpillars, and leaf-rolling worms, which can be controlled by spraying omethoate or fenitrothion at 1000-1500 times dilution mixed with 0.3-0.4% urea as a pesticide-fertilizer spray, with good results. Pests and diseases of potted chrysanthemums should be prevented and treated early; once the plant is damaged and leaves fall off, it causes irreparable loss to the potted chrysanthemum and also greatly reduces its ornamental effect.
In addition, an effective way to prevent leaf drop on the lower part of potted chrysanthemum plants and the “bare-legged stalk” is to fill the pot with growing medium in layers and stages. When the chrysanthemum cuttings are finally planted in the growing pot, first fill 1/3 of the growing pot with nutrient soil, and as the chrysanthemum seedlings root and the plants grow upward, fill in soil in stages and layers, until the pot is filled with soil when the chrysanthemums have formed buds, leaving only a 2-3 cm watering space at the rim of the pot so that water and fertilizer solution do not flow out. In the final filling, mix in another 1/3 of decomposed dry manure powder.
How to Fertilize Chrysanthemums
When repotting chrysanthemums, add an appropriate amount of fertilizer to the soil, which can make the chrysanthemums grow more healthily, but note that the size of the pot should be determined by the plant and should not be too large or too small. As the plant gradually grows, the flower pot can be changed to a larger one bit by bit.
Chrysanthemums love fertilizer, but improper fertilization will make them grow leggy. Therefore, when applying base fertilizer to chrysanthemums, potassium and phosphorus fertilizer can be used as the main fertilizer. The fertilization time should not be too early either; it can be chosen from the Start of Autumn until before the plant blooms, and during this period you must ensure the chrysanthemum has ample fertilizer and water. When fertilizing, the concentration of the fertilizer can be gradually increased.
At the small seedling stage, chrysanthemums need a relatively small amount of fertilizer, and you can fertilize once every week or a day or two more than a week, using dilute liquid fertilizer; during the growing period, as the seedlings slowly grow, the fertilizer they need also increases, and at this time you can increase the frequency of fertilization, applying once every about 5 to 7 days; then from July to August, when temperatures are at their highest, reduce fertilization appropriately so that the growing chrysanthemums pass through summer safely; from September to October, as temperatures gradually drop, this is also the period of the plant's most vigorous growth, and while increasing the frequency of fertilization you can also increase its concentration.
Chrysanthemum Grafting Methods
The cleft grafting method. Select a chrysanthemum seedling shoot tip 5-7 cm long as the scion, leave two or three leaves at the top, and remove the larger leaves on the lower part. Then use a double-edged blade to cut the scion into a 1.5 cm long wedge shape; after cutting, hold it in your mouth, being careful to avoid getting saliva on it. Then cut off the rootstock at the grafting site; the method is to split the rootstock straight down the middle with a knife, to a depth slightly longer than or equal to the cut surface of the scion (1.5-2 cm). Insert the scion into the split opening, align the cambium layers of both, wind plastic strips tightly around the joint from top to bottom, and smear mud on the cross-section to achieve a moisture-retaining effect. Finally, put the previously prepared plastic bag over it and tie the bag opening securely. Special reminder: when putting on the plastic bag, be sure to put the scion together with the several mugwort leaves below the joint into the bag.
In the process of cultivating chrysanthemums, problems that threaten their growth will inevitably arise, but the main cause of these problems is that the chrysanthemum is not suited to its environment. Therefore, it is necessary for us to make appropriate adjustments to the growing environment of chrysanthemums according to their growth habits, so as to ensure their normal growth.