Desert cacti turn brown and soft because of root rot due to overwatering and poor drainage. Cacti turn brown at the base due to basal stem rot which is caused by overly damp soil due to overwatering during Winter. A cactus that is turning brown and shrinking indicates the cacti is underwatered.
The surface of the cacti can turn brown with a rough texture due to corking which is typically as a result of underwatering in Summer, physical damage to the surface, or a sudden drop in temperature.
Keep reading to learn why your cactus is turning brown and how to implement the solutions to save your cactus…
Why is my Cactus Turning Brown (and Yellow) and Soft? (Overwatering and Poor Drainage)
Most houseplant cacti species have specifically adapted to growing in arid climates with low rainfall, low humidity, and fast-draining sandy soil that does not retain much moisture.
To grow cacti indoors successfully and avoid the cactus stem from rotting and turning brown, soft, and mushy it is important to replicate some of the conditions of its native environment by planting the cactus in, gritty well-draining potting soil that drains efficiently and only watering when the soil has dried out.
Watering a cactus too often or planting it in ordinary potting soil which stays damp for too long means there is too much moisture around the cacti’s roots for this drought resistant desert plant to tolerate.
Damp soil promotes the conditions for the cactus to develop stem rot and root rot which results in the stem turning brown and soft in texture.
As cactus plants are so well adapted to drought, it is important to wait until the potting soil has dried out completely between each bout of watering.
Consider that a mature Barrel cactus can often be neglected for as long as three months without watering and without suffering any ill effects due to its superior ability to store moisture and tolerate drought.
Cacti also need to be watered less often in Winter as they are typically dormant at this time which reduces their demand for water and because the roots are not uptaking moisture, the soil stays damp for long which results in soft brown and yellow cacti stems.
It is also important the cactus is planted in a pot that has drainage holes in the bottom to allow excess water to escape and that you empty any saucers or trays underneath the pot of excess water regularly to allow the soil to drain properly to avoid root rot.
How to Save a Cactus that is Turning Brown and Soft
- Reduce how often you water your cactus. Always wait until the soil has dried out completely before watering again, then water with a generous soak, ensuring that the potting soil is evenly moist. Watering cactus like this replicates the -deluge of rainfall, followed by a period of drought- cycle of soil moisture that the cactus typically experiences in its native environment.
To establish the correct watering schedule for your cactus in your climate, feel the potting soil at the bottom of the soil through the drainage hole in the base. If the soil feels damp then delay watering. If the soil has dried out then this is the perfect time for watering.
This meets the cactus’s watering requirements without risking root rot and brown rotting stems.
- Once the potting soil has dried out take the cactus out of the soil and inspect the roots. The roots of a cactus should be light colored (sometimes discolored slightly brown due to the soil) and feel firm, whereas rotting roots appear dark brown, with a slimy or mushy texture and an unpleasant smell. Cut any brown, rotting roots back to the base with a pair of pruners.
- Wipe the blades of the pruners with a cloth soaked in disinfectant, between each cut to prevent spreading the fungal pathogens that are responsible for the rot from diseased roots to otherwise healthy roots.
- Replant the cactus in a well-draining succulent and cacti potting mix. This potting mix replicates the cacti’s natural well-draining, gritty, porous soil structure which increases the rate of drainage and significantly reduces the risk of the cactus turning brown and soft due to root rot.
- Clean the cactus’s pot with disinfectant prior to repotting as the pot can harbor the fungal pathogens that are responsible for root rot.
- Plant the cactus in a pot with drainage holes in the base and ideally use a terracotta or unglazed clay pot as they are porous and allow the soil to dry out more evenly. Cactus plants are able to grow in plastic and ceramic pots but these materials are impermeable and retain more moisture which can increase the risk of root rot.
Avoid repotting a cactus in a pot that is too large as larger pots have a greater capacity for soil and therefore a greater capacity for retaining moisture, which can also promote the conditions for root rot.
You can either repot the cactus in its original pot or a pot of similar size to ensure that the soil dries out at a similar rate.
Once you have created the optimal conditions for your cactus (by watering less often and replacing the soil) and snipped back any diseased roots, the cactus can start to grow new roots and revive.
However, if the brown soft area of the cactus is increasing in size then if possible you can cut these brown rotting sections of the cactus back with a sharp blade to prevent the rot from spreading.
Whether or not the cactus recovers depends on the severity of the rotting. A great last resort is to propagate the cactus which can be done with offsetts, pads, or cuttings from any remaining healthy tissue.
Propagating cacti is a fun, easy project that can be the only way to save your soft, brown rotting cacti. Watch this YouTube video for how to propagate cacti:
Cactus Turning Brown at the Base of the Plant
The reason cacti turn brown at the base of the plant is because of basal rot disease which is caused by overwatering and moisture-retentive soils. Basal stem rot causes the cactus to turn brown and rotten at the soil line which can cause the cactus to droop and fall.
As desert cacti are mostly native to desert areas of Mexico and the United States, they do not tolerate damp conditions well at all.
Desert cacti need a ‘rest’ in Winter as part of their seasonal cycle with reduced watering, cooler temperature, and less fertilizer to prevent developing basal stem rot.
How to Save a Cactus That is Turning Brown and Dying from the Bottom
If watering persists at the same frequency in Winter then this is usually the cause of rotting stem at the base of the plant which can spread upwards and cause the cactus to die back.
This emphasizes the importance of adjusting your watering schedule in the Fall and Winter and the importance of a well draining succulent and cacti potting medium.
It takes longer for the potting soil to dry in Winter as the cactus does not draw up water at anywhere near the same rate and it may only be necessary to water your cactus once or twice in Winter (always feel the potting soil at the base of the pot through the drainage holes to assess whether the soil has dried properly before watering).
Address any watering problems and re-pot your cacti into well-draining potting soil. To be honest I find it difficult to revive a cactus with basal stem rot, so I recommend propagating the cactus from any off-sets, pads, or cuttings.
Propagating as a means of saving the cactus from basal rot can be particularly effective as the rot is unlikely to have traveled and infected other parts of the cactus, therefore there is often a lot of healthy tissue from which to make a cutting.
Watch the YouTube video further up this article for a great visual guide to propagating cacti.
Cactus Turning Brown and Shrinking
A cactus that is turning brown and shrinking in size indicates that the cactus is not being watered generously enough.
Sometimes the advice that ‘cacti do not need much water’ is misinterpreted to mean that cacti do not require a great volume of water when watering.
However the potting soil of the cacti should be watered thoroughly, so that excess water trickles from the base of the pot to ensure the soil is evenly moist, then allowed to dry out before watering again.
The cactus likes evenly moist soil after watering from which it can draw up and store the moisture it requires in its fleshy watering-storing stem.
If you water the cactus too lightly then only the top inch or so of the potting soil becomes moist and the water does not infiltrate the soil properly to reach the roots where it is required.
When the cactus is underwatered, the cactus has to deplete the moisture reserves in the stem which means the entire cactus shrinks in size and turns brown as a sign of stress.
How to Save a Cactus That is Turning Brown and Shrinking
Every time you water your cactus, water thoroughly to the extent that excess water trickles from the drainage holes in the base of the pot.
This ensures that the water has infiltrated the soil so that it is evenly moist to allow the roots to access the moisture they require.
After one or two watering cycles the cactus should replenish its moisture reserves which means the cacti should regain its size from its previously shrunken state.
Ensure that the cactus is not directly next to a source of indoor heating. The cacti can tolerate the heat but if the pot gets too hot then this can dry out the soil particularly quickly and result in drought stress.
Cactus Turning Brown Due to Corking
If your cactus has a section that is brown, dry, somewhat deformed with a rough texture on the surface then this is known as corking which can be an indication of physical trauma, a sudden drop in temperature, or underwatering in Summer.
Corking can also be a natural process as the cactus matures.
Fortunately, the corking does not mean the cactus is dying although there may need to be some adjustments made to the cultivation to ensure the cacti is healthy and not stressed.
Cacti are native to warm climates (but can tolerate cold nights) and prefer normal household room temperatures in the Summer but cacti do not tolerate chilling below 40°F in Winter.
Desert cacti thrive at room temperature, so this is not necessarily a big problem for most of the year, but it can be if the cactus is on a draughty window sill in Winter.
During Winter, the temperature can be high during the day and into the evening because of indoor heating, but there can be a significant and sudden drop at night, so ensure that cactus is kept in a room that stays above at least 40 (4°C), but ideally warmer.
The specifics of the temperature range are less important as cacti can endure w wide range of temperatures, but it is important to avoid a sudden temperature drop.
Always water the cactus with a generous soak in Summer ensuring the potting soil is evenly moist. A good way to establish whether the soil is evenly moist is by lifting the cactus’s pot and assessing the weight as the pot should be notably heavier if the water has properly infiltrated.
Wait until the soil dries out before watering again and this should prevent the corking appearance on the surface of the cacti.
The actually brown corking does not turn green again, even if the environmental problems have been addressed, but it also does not harm the cactus.
(To learn more, read my article, how to revive a dying cactus).
- Cacti turn brown and soft if they are overwatered. Cacti are drought-resistant plants that do not tolerate damp, moisture-retentive soils as this causes root rot. Cacti should only be watered when the potting soil has dried out completely to prevent it from turning brown and dying.
- Cacti turn brown at the base of the plant due to basal stem rot which is a symptom of overwatering. Once the rot develops at the bottom of the cacti it can fall or droop at which point it can be very difficult to save.
- If the cactus is shrinking and turning brown, this indicates the cactus is underwatered in Summer. Cacti need a good soak so that the potting soil is evenly moist. If the soil is watered too lightly then the moisture does not reach the roots where it is needed and the cactus draws from its moisture reserves in the stem, causing it to shrink.
- Cactus can turn brown on the surface with a rough texture due to ‘corking’ which is due to underwatering in Summer, physical injury, or a sudden drop in temperature.
- To save a cactus that is turning brown and soft recreate the conditions of the cacti’s native environment by only watering when the potting soil is dry, and repot the cactus in well-draining, gritty soil. Cut back any diseased roots and cut any brown, rotting sections of the cactus back.