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It's a big annoyance when the newly bought pillar cactus or the porcupine cactus that you've been given as a gift suddenly becomes shriveled or mushy. Irrigation often plays a major role, which leads to putrefaction processes. But other causes can also cause the cactus to rot. In many cases, you can save the succulent if it hasn't completely softened. Therefore, you should act quickly at the first sign.

cactus rot

If the kakus suddenly becomes soft and mushy, the signs are usually clear: it is rotting. In the following article you can find out why the cactus is rotting and whether and how you can save the plant.


There are various reasons why the plant tissue suddenly becomes soft. The exotic plants have very special requirements in terms of substrate and environment, because they have adapted to the conditions in their natural habitat with their growth. If the light, water and temperature are not right, vitality is impaired.


If the cactus develops yellow spots on the upper parts that soften over time, too much sunlight can be the cause. This phenomenon often occurs in spring when the cacti are taken out of their winter quarters and placed directly in the sun. Many green species like it warm, but do not tolerate direct sunlight. They grow in their homeland between tall shrubs and bushes. Raindrops increase the development of sunburn because they act like a magnifying glass. How to save the cactus:

  • place in a semi-shady place
  • Cut off the yellow parts of the plant
  • water very sparingly

notice: Did you know that the yellow spots become lignified over time? However, this can take a long time and carries the risk of further rotting processes if the care is not correct.

Lack of light and excess water

A typical phenomenon in columnar cacti is that the base remains thin while the top develops magnificently. The area above the root collar becomes soft and appears much lighter than the healthy part. Because the cactus lacks stability, it can no longer grow upright and collapses. Cacti develop such growth forms when they get too little light and too much water. Similar phenomena also occur with spherical cacti, which grow taller and taller. The stunted growth favors rotting processes, as the base of the trunk gets less and less light. You should act at the latest when the tissue becomes muddy.

root rot

If the exotic plant is watered too often so that water collects in the substrate, the roots can rot. The succulents are very sensitive to waterlogging because they are adapted to dry locations. When the fine roots rot, they provide an ideal breeding ground for fungal spores. Harmful fungi such as Botrytis or Phytophthora are often involved in root rot. They penetrate the organism via the damaged roots and spread there. As a result, the stem can rot. If the base of the cactus is already badly rotting and therefore appears soft and muddy, quick help is advised.

Wrong substrate

In nursery windows you may have seen cacti growing in aquariums filled with Seramis. But if you recreate this arrangement at home, you will soon be able to observe brown spots at the base. If you don't act quickly, the cactus will rot and become shriveled. Seramis consists of fired clay, which has a porous structure and dusts. These clay balls store water and continuously release it. However, cacti cannot grow in pure clay. Their roots are too moist in the substrate and at the same time the fine clay dust can become a problem if it settles on the fine roots. Cacti require little humus and large amounts of mineral rock. If you still don't want to do without the arrangement in the aquarium, you should proceed as follows:

  • Fill the base about three centimeters high with Seramis
  • pour a mixture of cactus soil, quartz sand and fine gravel on top
  • Plant cacti and leave the root neck free
  • fill up to the base of the trunk with gravel
  • water carefully to prevent waterlogging

First aid to lazy tribe base

If the rot is not too far advanced, the cactus can be saved. It is important that the upper part is still healthy and the tissue is not shriveled or mushy. Handle the cactus with thick gloves or a piece of paper to prevent spikes from penetrating the skin. Cut off the healthy part with a sharp and sanitized knife. There must be no rotten spots. Treat the wound with charcoal. It ensures that the interface does not become infected.

tip: Euphorbias can also be saved in this way. To stop the bleeding after the cut, you should hold the cut part under warm water for a few minutes.

let the wound dry

It is important that the interface is dried before planting. In many cases, rooting also works when cacti have been stuck into the substrate with a weeping wound. But here there is a risk that the healthy part of the cactus will also rot in the substrate. Therefore, wait at least 24 hours before inserting the cactus into the substrate. Their tissue functions as a water reservoir so that the plants can lie dry for a long time. If a hardened layer forms on the wound, you do not have to worry. This so-called callus is a superficial wound cork. It protects the open area and ensures that no mold spores or pathogens can settle. Root formation takes place at the edge tissue.


After the separated part has dried, it is encouraged to root in a special substrate for cacti. In order to achieve the greatest possible success, you should mix your own mineral-rich substrate. Cacti are adapted to nutrient-poor locations and need humus-free substrate, even if many hobby gardeners cultivate their cacti in potting soil. When buying cactus soil, pay attention to the composition. The products often contain peat, the degradation of which causes the peatland to recede.

  • Equip the planter with drainage and fill it
  • Moisten the substrate slightly
  • Press the cactus carefully into the substrate

Further care

You can try to save both the lower and the upper part. This only works if no rot has developed. Place the jars in a light location. The substrate in both pots should not be watered for the next week. Cacti root at different speeds. In some specimens, new roots can be seen within a few days, while other individuals require between six weeks and three months for root development. In some cases, the lower part regenerates when it receives more light again. The wound will lignify over time and the plant will sprout again at the edges.

tip: Always make sure that the ratio between light and water is balanced. Deficiency symptoms with subsequent putrefaction processes only occur when there is an imbalance.


Many cacti develop multiple shoots or offshoots, which you can recognize by constrictions. Should your cactus develop such offshoots, you can simply cut them off at the constriction and root them in a nutrient-poor and mineral-rich substrate. So you can not only save rotten cacti, but also rejuvenate and multiply them at the same time.

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