Does black rot in succulents spread to other plants in the same pot?

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Regardless of whether it is for beauty or because there are not enough pots, growing succulents together in a combined pot is a very common thing. Since many succulents are grown together, it is natural to encounter the situation where one succulent in the combined pot develops black rot and dies.

Once this happens, it makes people very worried: since black rot is a fungal infection, will it spread? Will it infect this one and then go on to infect another? This is a very natural worry. Even if I say it will not, I estimate everyone still will not believe it.

We have all bought whole boxes of fruit. If the fruit box is not ventilated, or if you eat too slowly, a small amount of fruit will rot. At first there seems to be no problem, and the rot only occurs on one or two not-so-strong fruits, but once the outer skin of the fruit is covered with blue mold, the rot immediately spreads throughout the entire fruit box. As long as other fruits come into contact with the blue mold, they will rot within a very short time.

So judging by the principle of fruit rotting, if one succulent in a combined pot develops black rot, the surrounding succulents should all be infected, and then it should quickly spread through the entire pot until all the succulents in the pot die.

However, hobbyists who have experienced black rot in a combined pot can all testify that black rot disease in a combined pot does not spread as wildly as rot in a fruit box. Below let us compare the differences between black rot incidents in flower pots and fruit rot incidents.

Fruit is also a succulent, juicy thing. However, they are different from succulents planted in pots: after they are picked from the tree, they enter a dormant state. Fruits are indeed still alive, but their life activities drop to a very low level, maintaining cell survival and the conversion of sugars within the cells only through the energy provided by respiration. Since the value of the nutrients in fruit is inherently to rot and then serve as fertilizer for their own seeds, they not only do not mind, but actually welcome mold to eat their flesh.

But succulents planted in flower pots are completely different. Healthy succulents have quite strong self-repair ability and will not be slaughtered at will like fruit in a fruit box. If the epidermis of a succulent is infected, usually the succulent can stop the fungus from invading through rapid repair. When a succulent truly develops black rot, usually the mold has already entered the succulent's body through a wound in the epidermis. Against this strange attack method, like Sun Wukong burrowing into Princess Iron Fan's belly, succulents often lack defensive ability (never mind succulents, even demons with thousands of years of cultivation cannot withstand it).

When fungi enter the succulent's body, they will multiply in large numbers along the ducts that transport water through the succulent, and soon the entire succulent will turn black. But for other succulents growing in the same pot, as long as the fungi do not enter the succulent's body, even if the fungal density in the potting soil is very high, it will not trigger black rot. So in most cases, you do not even need to pay attention to the succulent that has developed black rot. You can perform surgery such as beheading and pulling off leaves for the black-rotted succulent without digging it out. Then wait until the black rot has completely ended (the stem and leaves have completely dried up), and gently pull out the dead succulent's corpse.

Why not immediately dig out the black-rotted succulent as soon as black rot is discovered? This is because, in a combined pot, the succulents are planted relatively densely, and the root systems between the succulents often become tangled together. If you dig on a large scale just when black rot has occurred, it is very easy to injure other healthy succulents. When the roots of healthy succulents are injured, they very easily become the next target of fungal attack. This instead easily leads to new black rot occurring. But if you leave it alone, the fungi will, due to excessive reproduction, also die in large numbers after the nutrients of the dead succulent are consumed. The density of the fungal community will naturally drop to a normal level. At that time the surrounding succulents are safe.

There is one kind of black rot in a combined pot that requires special attention, namely black rot caused by care mistakes. For example, you clearly know that you watered too much and caused water accumulation in the flower pot, or they have just experienced pest damage or sunburn. At this time, if you find that one succulent in the flower pot has developed black rot, since all the succulents in the flower pot have experienced the same conditions, black rot may very likely occur one after another, and this should attract considerable attention.

If, when you discover black rot in a succulent, the soil in the flower pot is still very wet, and perhaps the weather is also not very good at the same time, then you should consider whether the other succulents are also in a condition of being suffocated. When the potting soil is very wet, it is not suitable to use carbendazim as a root drench again. Because under airtight conditions, the root system of the succulent has very limited ability to absorb the medicine, and drenching the roots again will make the potting soil even less breathable. This practice is not only unhelpful, but harmful. So when black rot occurs in wet soil, the first priority is ventilation and breathability. Especially for soil with more peat that easily becomes airtight, you can use a tool with a relatively rounded tip (such as a seedling transplanter) to help loosen the soil and let the succulent breathe, and strengthen ventilation. After the potting soil dries a bit, breathability will recover, and at that time the succulents are safe.

If pests are also found in the flower pot where black rot has occurred, it is very likely that the black rot was caused by wounds from pest bites. At this time, observe the other succulents. If the other succulents are in relatively healthy condition and no wilting has occurred, there is no need to make a big move by removing all the soil from the whole pot and washing the roots. Just use insecticide as a root drench and pay attention to observation in the near future.

To sum up, black rot can be said not to be contagious. However, under adverse environmental conditions that easily cause black rot, succulents indeed may develop black rot one after another. At this time, improving the growing environment for the succulents is more effective than treating them individually.

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