What causes the mass yellowing and falling of leaves on roses and Chinese roses?
You may not be aware of the small experiences of plant cultivation regarding the mass yellowing and falling of leaves on roses and Chinese roses, which are very useful tips worth collecting!
Recently, many flower enthusiasts have noticed this issue: Chinese roses are prone to yellowing and falling leaves, and there are also spots on the yellow leaves. Why is this happening?
In the past, it was rare for Chinese roses to have yellow leaves in March and April, but this year it seems to have become a common phenomenon, with a large number of yellow leaves appearing as early as March. I have analyzed the following three reasons for this phenomenon.
Reasons for the mass yellowing of leaves on Chinese roses in spring
1. Metabolic yellowing
In previous years, winters were quite cold, and Chinese roses in frost areas would shed leaves and hibernate. However, last winter was very warm. Taking the Chinese roses in our Jiangsu and Zhejiang areas as an example, many did not shed leaves, and some even sprouted new buds early.
But due to the unstable temperature, the growth of new buds is slow, and after two or three months of growth and exposure to wind and frost, they are now relatively old. The growth of new leaves consumes a lot of nutrients, so these old leaves naturally need to be eliminated because their ability to produce nutrients is very weak. Keeping them would only increase consumption. The natural metabolism of Chinese roses will淘汰 these old leaves, and for this type of metabolic yellowing, it's actually fine to remove them without too much concern.
2. Black spot disease
This spring, in addition to the obvious increase in metabolic yellowing, black spot disease has also appeared early. In previous years, by March, black spot disease was not present in the Zhejiang area, or if it did occur, it was very rare. However, this year, the爆发 time of black spot disease has clearly been提前.
This should also be caused by the warm winter last year. We even cleaned the garden with lime sulfur mixture in winter, but it still feels that there are more diseases and pests than in previous years. Therefore, flower enthusiasts who grow Chinese roses should also be more vigilant and basically start the "medicine cannot stop" mode from now on.
When you find that the leaves of Chinese roses turn yellow and are accompanied by black spots, please remove the yellow leaves in time and then use fungicides for a comprehensive spray to prevent black spot disease. Fungicides such as carbendazim and mancozeb can be used.
If you are growing Chinese roses on a balcony and have a small number of them, you can spray fungicides by diluting alcohol 500 times. If you don't have alcohol, edible vinegar can also be used. Diluting edible vinegar 200 times and spraying can also have fungicidal and disease prevention effects.
3. Drought
Many flower enthusiasts think that yellowing of Chinese roses due to drought is rare, but in fact, it is very common, especially in areas with more rainfall.
Many areas have a high frequency of rain in spring, but in fact, the rain is not heavy, it just rains a little every day. The surface of the potting soil is moist, but the soil below is dry. In the eyes of our flower enthusiast friends, it seems that it won't dry out because it rains every day, but in fact, the potting soil has already dried out.
Therefore, if it has been a long time since watering and a large number of yellow leaves appear on Chinese roses without black spot disease, you should check the moisture level of the potting soil to avoid yellowing of Chinese roses due to drought caused by relying on rain for watering.
I hope the detailed introduction above about the mass yellowing and falling of leaves on roses and Chinese roses is clear to you.