1, potted plants should not be watered too much: because potted plants are placed in a cool or slightly sunny place indoors, watering potted plants too much will make the soil of potted plants wet and waterlogged, which will lead to root suffocation and decay and leaves falling off again. Therefore, indoor watering of potted plants should adhere to the principle of "seeing dry and wet, then watering thoroughly", and do not water sporadically or excessively.

2. Potted plants should not be over-fertilized or under-fertilized: long-term fertilization in potted plants will cause yellow leaves; Too much fertilization, potted plants can not absorb burned roots, can not absorb water, but also lead to yellow leaves falling off. Usually, indoor potted plants are applied with thin fertilizer in late spring and every other week in summer and autumn. Don't apply thicker fertilizer. If there is too much fertilization, some fertilizers in the soil can be diluted and washed away by watering more. Lack of fertilizer will lead to hardening of basin soil, yellowing of potted leaves and slender yellow branches. At this time, fertilizer should be applied immediately, and it will be effective within one week.

3. Potted plants should not have too much or too little light: it depends on the growth characteristics of potted plants.

As for the long black spot, it may be black spot disease, which is widely distributed and seriously harmful, because the pathogen is mycelium or sessile bacteria in dead branches or soil. Infection began in the middle and late May of the following year, and the peak period was July-September. Conidia spread, expand and reinfect by wind, rain or insects. Rainwater is the main condition for the epidemic of diseases, and the onset is early and severe in years with early and abundant rain. Low-lying stagnant water, poor ventilation, insufficient light and improper fertilizer and water are all conducive to the onset. After autumn, litter can be removed, burned in time, cultivation management should be strengthened, plastic pruning should be paid attention to, and ventilation and light transmission should be ensured. Spraying 50% carbendazim wettable powder 500- 1000 times, or 75% chlorothalonil 500 times, or 80% zineb 500 times for 7- 10 days, for 3-4 times.