Why the leaves of Magnolia grandiflora dried up and fell off

There is a letter from a reader in Tianjin: two pots of grafted magnolia were bought four years ago, but they used to grow well. Yellow leaves appeared in the winter in the flower cellar last year, and then gradually developed into half of the leaves scorched and fell off. After coming out of the cellar in May this year, the new leaves became semi-dry soon, and it was even more serious from July to August. It was thought to be caused by fungi, but it was ineffective after medication. What is the cause of this, please? What rescue measures should be taken?

Answer: your magnolia leaves dry and fall off phenomenon, there may be the following reasons: first, the cellar time is too early, the cellar temperature is too high, poor ventilation, resulting in leaves during the overwintering, and the new leaves grow poorly and semi-withered. The second is to get out of the cellar without adaptive exercise, so that it can not face to adapt to the environment outside the cellar, resulting in new leaves falling off. Third, the summer ambient temperature is too high, the light is too strong, and the ventilation condition is poor. Fourth, the basin soil did not turn the basin and change the soil for a long time, so that the root tip of the fleshy nutrition was pressed against the basin wall, resulting in burns at the root tip during high temperature drying, resulting in semi-withered leaves; in addition, malnutrition caused leaves to yellowing; soil consolidation and too much moisture caused rotten roots and withered leaves; insufficient acidity of irrigation water and high salt content would cause leaves to yellowed and semi-withered leaves.

The measures that should be taken are as follows: first, before entering the cellar in winter, all dead leaves and old leaves should be picked and burned to reduce the possibility of leaf spot disease. Second, the time of entering the cellar should wait until the temperature drops to 0 ℃, and the temperature in the cellar should be reduced during the overwintering period, so as to keep the basin soil from freezing, and it is best not to send out new leaves when the plant comes out of the cellar. You can also consider burying it with a basin in a leeward-facing seedbed. The aboveground part is wrapped in straw or film. It can withstand at least a low temperature of-12 ℃. Be careful not to freeze the roots. Third, from June to August, potted plants can be transferred to cool and ventilated places that can avoid the sun, and often spray water to the plants and the surrounding environment to create a cool and warm semi-shady environment. Fourth, when coming out of the house in spring, turn the pot to change the soil, replace it with a flowerpot slightly larger than the original pot, cut off the necrotic root system, cut off the hardened soil, and re-plant it with loose, fertile and well-drained acid culture soil. Fifth, pay attention to loosen the soil and fertilize regularly during the growing season, and add 0.1% ferrous sulfate powder to the irrigation water, which can promote the vigorous growth of the plant, avoid physiological yellowing, and lay a good nutritional foundation for good flowering and more flowering in the coming year.