What is the reason for the black stem appearing on the rose of Sharon?
Are you curious about the small green plant maintenance tips for why the rose of Sharon has a black stem? Let's introduce them next.
What is the reason for the black stem appearing on the rose of Sharon? These four points should not be ignored...
Recently, many flower friends have consulted about the black stem problem of roses. Indeed, due to the abnormal weather lately, roses are more likely to develop black stems. So let's summarize and analyze the causes of rose black stems and the corresponding preventive measures.
Rose Black Stem Causes and Preventive Measures
The phenomenon of black stems in roses is more common in high-temperature seasons in summer and rainy seasons. Summing up its causes, there are mainly the following three.
1. Fertilizer Damage
Fertilizer damage leading to black stems in roses is most likely to occur in the high-temperature season of summer. There are two main types of fertilizer damage: one caused by fast-acting fertilizers and the other by slow-release fertilizers.
The fertilizer damage caused by fast-acting fertilizers is easy to understand; it is caused by too high a concentration of water-soluble fertilizers, leading to root damage. In spring, fertilizer damage in roses often manifests as yellowing and drying of leaf tips, but in hot weather, fertilizer damage can easily cause black stems in roses, and it is a black stem from the bottom up.
Because when it is hot in summer, the growth of roses often slows down, while the release rate of fertilizer accelerates. Not only fast-acting fertilizers, but slow-release fertilizers can also release too quickly at high temperatures, causing fertilizer damage and black stems without realizing it.
Therefore, in the book "How to Grow Roses from Scratch," it is always emphasized that slow-release fertilizers should not be mixed with soil, to avoid having no good rescue methods when fertilizer damage occurs.
Besides slow-release and fast-acting fertilizers, organic fertilizers can also cause black stems. It is mainly because our flower friends apply fertilizers too close to the roots. Many friends pile fertilizers directly on the main root area of roses, and during hot weather, fertilizer damage black stems can easily occur.
To avoid fertilizer damage black stems, we need to pay attention to the following: during hot weather, top dressing should be done as late as possible in the evening, with a low concentration. When rose growth stops, fast-acting water-soluble fertilizers should be discontinued. If roses continue to grow, fertilization should be maintained, but it is best to apply thin and frequent fertilizers.
In addition, slow-release fertilizers, controlled-release fertilizers, and fermented organic fertilizers should be kept away from the roots. For potted roses, they can be shallowly buried or evenly applied around the pot edge. Do not pile them in one place, and especially not directly on the main root.
2. Root Suffocation
Besides fertilizer damage, root suffocation is also a very important cause of black stems. Especially in summer, when the pot is very hot from the sun, the high temperature of the potting soil can cause the roots of the rose to be in a hot and humid state if watered in the morning, leading to root suffocation.
Moreover, with too much sun exposure and thin pot walls, the capillary roots can easily be scorched to death, and with a bit of fertilizer added, it's hard for roses not to develop black stems.
Watering in summer is best done in the evening. If watering in the morning, it should be done early to avoid direct sunlight on the pot.
3. Fungal Infection
During rainy periods, fungal infections can also be an important cause of black stems in roses. Especially when rose branches have wounds and it rains continuously, it can easily cause wound infections, leading to black stems in roses. This type of black stem usually starts from the top and has little impact if dealt with promptly.
We should avoid pruning roses in rainy or cloudy weather, as it can greatly increase the probability of black stems in roses. So don't prune in the rain.
Of course, even if we don't prune in the rain, roses may still develop infections from wounds. This can be caused by insects damaging the epidermis of rose branches or dense foliage that leads to poor ventilation, causing diseases that result in black stems, which often start in the middle.
Rose black stems, as long as they don't start from the bottom, have a chance of recovery. Generally, completely cutting them off and applying mycillin can inhibit the further occurrence of black stems.
If black stems have already spread to the bottom, it's not necessarily a lost cause. If new sprouts can grow before the complete blackening, there is a chance for revival.
This article shares a detailed explanation of the reasons for the black stem appearing on the rose of Sharon. I hope this article can provide you with help in green plant management!