Dahlia leaves turn yellow and black, mainly because the pot soil is too wet, or the cultivation land is low and stagnant; Root rot. Or improper fertilization, too high fertilizer concentration, fertilizer directly applied to the main roots, resulting in root burning. If the situation is not serious, loosen the pot soil appropriately, stop watering, and place it in a sunny place to avoid direct sunlight; Can gradually recover.

Dahlia is a fleshy and fat root, which is neither drought-tolerant nor afraid of waterlogging. Suitable for planting in loose, humus-rich, well-drained sandy loam or artificially prepared nutrient soil. If the pot soil is too wet, it is easy to cause root rot, so it is not allowed to water too much in winter.