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Actually, cacti are particularly easy-care plants that are also suitable for hobby gardeners who do not have a green thumb. But there are care mistakes that even a robust cactus will not forgive. Here you can find out why cacti turn yellow or brown and what you can do about it.
Cacti turn brown or yellow
Basically, a cactus is not difficult to cultivate. Nevertheless, it is mostly care mistakes that cause the succulent to become ill. Usually, a problem first manifests itself with a yellowing or browning of smaller parts of the tissue on the cactus's body. Since cacti occur in very different habitats, the plants have adapted accordingly. Nevertheless, most species have similar requirements:
- lots of light (except epiphytes)
- do not keep evenly moist
- annual dormancy in winter
causes
If cacti turn yellow or brown, quick action is required. Otherwise the damage can progress so far that the succulent can no longer be saved. There are a wide variety of possible causes, which almost always manifest themselves in similar symptoms.
1. Incorrect watering behavior
As a succulent plant, a cactus is adapted to a specific annual rhythm of rainy season (vegetative season) and dry season (resting phase). With us, the growth rhythm is regulated in such a way that the dry season falls in winter. In this way, the plants can cope better with the lack of winter light. In practice, this means: water regularly from spring to summer, little or not at all in winter.
waterlogging
One of the most common mistakes when cultivating cacti is overwatering them. Most species are extremely sensitive to excess moisture. As a rule, however, it is not the moisture that causes the plants to die, but harmful fungi such as Phytophthora or Botrytis, which penetrate the plant via the rotten, injured roots.
damage picture
- Spots on the cactus body (cacti first turn yellow, then brown)
- preferably at the base
- give way when you press on it with your finger
- rotting of the roots and the base of the trunk
remedy
In the early stages, it still helps to immediately remove the cactus from the pot and remove all soil from the roots. Cut back rotten roots to healthy, firm tissue. After drying, the plant can be used in fresh substrate. To avoid reinfection, it is best to use a new vessel right away. In the worst case, the rot has progressed so far that the entire base has softened. The only thing that helps here is to cut off the healthy part in the upper area and use it as a head cutting.
Cereus
Irregular watering
Watering at very irregular intervals - especially if the water is too cold - and excessive humidity can in extreme cases lead to unsightly discolouration of the plant body.
symptoms
- spots (brown or gray)
- mostly at the base
- spread upwards
measures
From now on, water the plant regularly during the vegetation phase with moderate amounts of stale, room-warm water.
By the way: With some cacti, corking at the base of the stem is a completely normal sign of aging and cannot be prevented even with perfect care.
dryness
Although cacti generally do not need a lot of water, they cannot do without it either. Regular watering is therefore essential, especially during the growing season. All species that develop leaves are affected particularly quickly.
- The leaves dry up and fall off
- Brown to gray coloration
- starting at the tips of the shoots
remedy
Only pouring helps here. However, you should not overdo it now, otherwise the plant threatens to rot. Water moderate amounts at regular intervals, and the prickly growths usually quickly come to life.
2. Unfavorable nutrient levels
over-fertilization
In nature, cacti prefer sandy, humus-poor soils that contain few nutrients. This does not mean that the prickly plant can do without any nutrient supply at all. Just in moderate amounts. Whoever means too well with fertilizing - especially with nitrogen - harms the plant more than it supports it.
damage picture
- some shoots of the cacti first turn yellow, then brown
- soft, spongy tissue
- increased risk of pest infestation
measures
When in doubt, it is better to fertilize a little too little than too much. Preferably use a special cactus fertilizer, the nutrients of which are tailored to the needs of the water-storing plant, as a universal fertilizer or a fertilizer for flowering plants.
accumulation of minerals
An accumulation of minerals such as lime on the porous inner wall of clay pots is usually associated with an increased pH value in the substrate.
symptoms
- delayed growth
- no flowering
- yellow shoot tips
- sometimes brown spots at the base
remedy
Remove as much of the old soil as possible, including on the surface of the substrate. The cactus is then planted in fresh, loose cactus substrate. At the same time, check whether all the roots are healthy and the plant may need a larger planter. Even if the pot is still big enough, cacti should be repotted every three years to change the soil.
nutrient deficiency
Too little fertilizer can also lead to discoloration. Therefore, use a special cactus fertilizer at regular intervals during the growth phase between spring and August as recommended on the packaging. Iron deficiency in particular is one of the most common causes of discoloration. Therefore, commercially available cactus fertilizers contain iron as a trace element.
damage picture
- Discoloration and spots on the plant body (usually brown to gray)
- growth disorders
- bloom inhibition
remedy
Since cacti are considered frugal, many hobby gardeners forget that they also need fresh substrate from time to time. Therefore, repot your cactus regularly. If the repotting is less than a year ago, balanced fertilization will help.
notice: The substrate in which the cacti are delivered is often of poor quality. It is therefore advisable to plant a new cactus in high-quality, fresh substrate.
3. Location error
cold damage
The succulent plants need to go through an annual dormant period for healthy growth. In the winter months, cacti should therefore be kept cool and dry. An exception are epiphytic species that need to be warm even in winter. However, most species do not tolerate temperatures below 10 °C or cold drafts.
damage picture
- parts of plants that appear glassy
- subsequent rotting or drying up
- Cacti turn brown
Observe the minimum temperature of the respective cactus species and avoid draughty or too cold locations. If only individual parts are affected, they can be cut out.
sunburn
Most cactus species wake up very slowly from their hibernation. For this reason, they should be gradually accustomed to the changed light conditions again in the spring. If the succulent's usual location is on a north, west, or east window, there's not much to worry about. However, completely unprotected south-facing windows can be too much for the plant at first - especially in the midday hours.
symptoms
- Discolouration of the upper layers of the skin
- initially red to yellow
- later brown
- only on the sunny side
- Extreme case: brown, sunken spots
measures
The cactus develops anthocyanin when exposed to extreme sunlight. This is a dye that protects it from further damage. For this reason, the damage is usually moderate if recognized early. So that the burns do not become more pronounced, you should immediately change the location or shade the plant. A light sunburn can regress in a semi-shady place.
By the way: Epiphytic plants do not tolerate full sun exposure, they should be cultivated in semi-shade.
4. Pests
Although insect pests and diseases are very rare in cacti, they still occur again and again, especially in weakened plants in the winter months. Even a newly bought cactus can already be infected. Among the most dangerous pests for cacti are spider mites and scale insects.
Symptoms of spider mite infestation
- whitish or brownish animals (often only recognizable with a magnifying glass)
- brown, scabby spots (in the axils or shoot tips)
- sometimes: yellow shoot tips
- increase over time
- with heavy infestation: white web
Spider mite infestation
Symptoms scale insects
- small brown bumps
- with severe infestation: yellowish discolouration
- especially at the shoot tip and on young shoots
measures
In order to prevent pests from being introduced with new plants, these should first be set up separately. If there are no symptoms or pests after several weeks, the cactus can be placed with the other conspecifics. In the event of an infestation, the affected plant should be treated accordingly. If this is already far advanced, it is better to destroy a single cactus to protect the rest of the cactus collection.
tip: Unlike many other plants, it is possible to use oleaginous remedies with good results on succulents. These clog the respiratory organs of the pests, causing them to die.
5. Diseases
Diseases caused by viruses, bacteria or fungi are very rare in cacti. As a rule, these germs are transmitted by insects or unclean, non-disinfected tools when cutting or grafting.
damage picture
- slimy, yellowish tissue: bacterial infection
- cauliflower-like growths: viral disease
- Death of the grafted segment
remedy
In the first-mentioned cases, rapid cutting out of the affected parts of the plant is essential for survival. Be sure to cut into the healthy tissue with a clean tool and disinfect the cut surface with fine charcoal. If the infection is already very advanced, the cactus can no longer be saved.
6. Intolerance to pesticides
Among the many different causes of a brown or yellow discoloration in cacti are pesticides. Various species of cacti are very sensitive to the use of agents against diseases and pests.
symptoms
- extensive yellow or brown discoloration
- sometimes only in the grooves
- softening of the tissue
- partial or complete death of the plant
measures
Most of the damage is irreversible. It is therefore important to test the product on just a few plants or shoots before spraying or treating the entire collection.
