Brown spots on Christmas cactus leaves are usually caused by diseases like root rot or stem rot, but pests and even sun scorch can also cause them.
This is a problem that I have dealt with myself, and in this guide, I’ll share the best tips for getting your Christmas cactus back to full health after it has suffered from brown spots.
Keep reading to learn the seven most common reasons for brown spots and what the chances of survival look like for your plant.
- 7 Causes Of Brown Spots On Christmas Cactus
- How To Save A Christmas Cactus With Brown Spots
- Preventing Brown Spots On Christmas Cactus
- In Summary
7 Causes Of Brown Spots On Christmas Cactus
Here are the seven most common reasons for brown spots on Christmas cactus leaves.
1. Root Rot
Root rot is a condition that affects the roots of Christmas cactus plants and is caused by extended periods of overwatered soil.
In overwatered conditions, root rot will become active in one of two ways:
- Dormant fungi in the soil that is favored in overwatered conditions.
- Roots that suffocate due to excess water will die and rot as they do so, which then spreads to other roots.
Root rot makes it difficult for nutrients and moisture to reach the leaves, causing them to turn yellow and brown and eventually die.
2. Soft Brown Scale
Brown soft scale insects can infest your Christmas cactus. These pests feed on plant sap, causing yellowing and brown spots on the leaves.
They can also be mistaken for brown spots themselves as they are small and brown.
As they feed on the sap found within the leaves, they secrete honeydew which gives them a sticky texture.
Mealybugs are another pest that can cause brown spots on Christmas cactus leaves.
They also feed on plant sap and excrete sticky honeydew, which can promote the growth of sooty mold.
Tissue damage and mold growth will cause several spots to form on the leaves, which can be brown, yellow, or even shades of grey due to the mold.
4. Fusarium Stem Rot
Fusarium stem rot is a fungal disease that causes brown spots on the stem at the soil line.
Fusarium stem rot is caused by the fungus Fusarium oxysporum f. sp. radicis – lycopersici, which also causes root rot.
Fusarium stem rot is practically impossible to reverse.
5. Basal Stem Rot
Basal stem rot is another common problem that affects Christmas cactus plants.
The symptoms are similar to fusarium stem rot, with brown spots appearing near the soil line.
Like fusarium stem rot, basal stem rot is also extremely difficult to reverse.
Too much direct sunlight can cause sunburn on Christmas cactus plants, leading to brown spots on the leaves.
These spots will usually be brown in the center with yellow halos, and leaves facing the sun are more prone to them.
One of my inspirations for writing this article was my own Christmas cactus plant that has suffered from brown spots due to underwatering.
Underwatering causes the leaves to lose moisture and form brown spots and edges as a result, and increases in temperature or decreases in humidity can make this more likely to occur.
In my case, I forgot to increase my watering schedule over the summer, and these brown edges appeared in a matter of weeks.
How To Save A Christmas Cactus With Brown Spots
The success rate of saving a Christmas cactus with brown spots depends entirely on the cause of the spots.
If you can catch the signs of root rot early on, then it is highly treatable. If the rot has spread into the stem, there’s very little chance of recovery.
Other issues like sunburn and underwatering are quite trivial to fix and only require pruning and a change of location, so skip ahead to the last part if you suspect this is the problem.
Identify The Cause
Several factors, including over-watering, pests, or diseases, could cause brown spots on your Christmas cactus.
Pests should be very easy to identify as they are visible to the eye, whereas diseases can be trickier to see.
If there is discoloration around the stem at the soil line, then this is a clear sign of stem rot.
Checking the soil and roots is a necessary part of this process as well to either identify or eliminate root rot as a problem.
To do this, gently remove your plant from its soil and brush away the soil around the roots.
If the roots are white and healthy, then root rot is not a problem, but if they are discolored, mushy, or smell bad, then root this will need to be addressed.
Pruning Affected Areas
Affected leaves and roots need to be pruned carefully with your preferred pruning tool.
This will help to stop the spread of disease and let the plant focus its recovery on existing healthy roots and leaves.
After pruning, treatments will need to be applied in the case of pests and diseases.
Fungicide can be applied to the remaining healthy roots to prevent root rot, and pests can be removed with a cotton bud and rubbing alcohol.
For large infestations, the remaining leaves will need to be treated with insecticidal soap, with repeat applications very likely being needed.
Repotting is important, especially after root rot, as it will stop any harmful fungus in the soil from spreading further, and it will freshen up the soil and help your cactus recover.
Succulent soil mixes work well for Christmas cactus plants, or you can use a mix of regular potting soil and perlite to improve drainage.
Optimize Other Care Conditions
Lastly, pay close attention to other care conditions to ensure your Christmas cactus thrives and recovers quickly.
Preventing Brown Spots On Christmas Cactus
It’s a whole lot easier to prevent brown spots on Christmas cactus plants in the first place than having to deal with the consequences, especially in severe cases of root and stem rot.
Here are some easy tips to make this possible:
Proper Plant Environment
Creating a suitable environment for your Christmas cactus can prevent brown spots from developing.
Choose a well-draining potting mix to protect your cactus from root rot, and don’t forget to use a pot with drainage holes.
Allow the soil to dry out to around one inch in depth between watering, but never let it become bone dry like I did. During winter, reduce watering as the plant enters a resting phase.
Avoid misting the plant as this only raises humidity temporarily, and it can attract pests.
Inspect your Christmas cactus regularly for any signs of pests or diseases.
If you spot any unhealthy or infected stem segments, prune them promptly and dispose of them carefully. Deal with pest infestations quickly before they spread and become difficult to control.
To keep your Christmas cactus healthy and prevent the development of brown spots, provide adequate nourishment and nutrition. Fertilize the soil every 4-6 weeks during the growing season using a balanced houseplant fertilizer.
In winter, cut back on fertilizer to let your cactus rest. However, don’t skip it entirely, as some nourishment is necessary for your plant’s overall health.
Rotate your cactus occasionally to ensure even exposure to light, which promotes balanced growth and flowering. By following these friendly tips, you can help your Christmas cactus flourish and prevent the appearance of brown spots.
Brown spots on Christmas cactus plants are usually either a result of pests or disease and can be controlled relatively easily.
It’s important to check the soil for signs of overwatering though, as any root rot will need to be addressed quickly to save your plant.
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