Indeed you have a pretty cactus doing great on your windowsill. Suddenly, you notice that it’s gradually turning yellow despite being given the usual care. What might be the cause of discoloration? Is there any way to solve it?
Cactus can get yellow due to 1) insufficient light source, 2) poor soil quality, 3) exposure to intense light, 4) pests infestation, 5) imbalance nutrients, 6) dehydration, 7) natural mutation, 8) fungal disease, and 9) exposure to extreme cold.
When a cactus gets yellow, it usually conveys that something is not right. It is paramount to diagnose why it turned yellow so you can immediately apply the needed solution to avoid further plant damage. I will walk you through each possible cause and the appropriate solution to fix your yellowing cactus.
A change in color on your cactus can tell about their condition. It may occur on any part of the cactus, depending on what causes the stress. While every situation is different, here are the general reasons why your cactus develops a yellow tint. Fortunately, the majority of them are reversible.
Cactus turns yellow in case of the limited amount of light it receives. Without adequate light, the cactus cannot produce sufficient chlorophyll and becomes pale.
Generally, cacti need light to survive and perform the essential processes to grow. The quantity and intensity of light needed by cacti depend on their species. If a cactus cannot get the sufficient amount of light it requires, chances are it will change its color from green to pale yellow.
Another indication that the cactus is not getting adequate light is if it starts to stretch or etiolate, leaning towards the light’s direction and developing a pointy pale tip that is soft to touch.
Too compact soil might end up holding too much water for an extended period. Cacti don’t like sitting on wet potting medium as their roots are prone to rot. Rotten roots will hinder nutrient and water uptake, making the cactus yellow from the base.
The appropriate soil type in growing cactus should drain rapidly and adequately while retaining a bit of moisture. It should be porous so that it will not stay wet for a long time when water passes through. On the contrary, using a dense and clayish soil mix encourages waterlogging and overwatering.
Here below is my usual choice for a good cactus mix.
It is likely to become compact and take more time to dry, so the roots are prone to rot. The fungus will also breed on the potting medium that remains wet for long. An early sign of root rot is yellowing on the bottom stem of the cactus that becomes soft and mushy later on.
Too much sunlight can get the cactus yellow as its epidermis gets scorched up. The discoloring starts from the top or on the area exposed to intense light. Cacti that are not adapted to sunny climates will likely get burned when placed outside to bask under the scorching sun for a long time.
While insufficient light will cause the cactus to turn yellow, too much light can do the same thing to the plant. You would probably think that all cactus can handle the hot sun, but it’s just a common cactus misconception. Not all cactus species need a lot of light to thrive.
Some cactus do better under a shade or just a partial sun. Yellowing due to sunburn can happen if you move your cactus from the shade and leave it in a sunny spot for too long. The cactus will get shocked as it is not used to the condition and therefore develop sun damage.
A cactus can get yellow as a consequence of a pest infestation that is damaging the area that starts paling. Harmful insects and bugs suck the sap out of the cactus stem, leaving an inconspicuous scar and dried-out plant tissues.
Pests such as scales and mealybugs are common cacti problems that cause the plant to develop yellow stems. They will build colonies, and the attack gets extreme and widespread. When this happens, the infected area will dry up, soften and discolor.
Shrinking and wilting on the stem are usual signs that develop along with yellow discoloration. This is due to water and nutrient loss as the pests feed on the cactus.
Excess or depleted nutrient levels have negative results on the cactus, including yellowing. In this case, it may not develop rapidly, but yellowish coloration begins on the base of the plant.
Cacti can get by with lesser nutrients and do not require frequent fertilization. However, some signs will show up once there is a deficiency or excess in mineral levels. Deficiency in potassium and nitrogen can lead to stem discoloration and paleness.
Moreover, if nitrogen and phosphorus in the soil are too high, roots will become brittle and rotten. Another reason why a cactus can be yellow is due to inadequate nutrient uptake by the roots.
Once a cactus doesn’t get sufficient water for a prolonged period, it will begin to shrivel and soften as it uses up all the available water in its body. Chlorophyll production will gradually reduce, then the plant will start getting yellow from the bottom.
Cacti have a lot of packets on their stem where they store water in preparation for drought. Although cacti can withstand several months without water, it needs a good drink from time to time, especially during hot days and the growing season.
A prolonged period with no water can deplete the cacti water storage triggering the first signs of dehydration. You can spot wrinkled and droopy stems that are soft to touch. Yellowing of the bottom soon follows, and on extreme dehydration, the cactus will shrink and wilt.
A variegated cactus develops a notable change in its color where patches and streaks of yellow or other colors appear. Variegation can be natural, but sometimes it is a product of species cross-hybridization. This is the only case where yellowing in the cactus is not a sign of a problem.
Sometimes, cacti undergo natural, spontaneous mutation in their forms and color. Variegation is one of the common forms of cactus mutation, where the green pigment is reduced and concealed by the yellow, red, or orange colors. Portions of the plant change color, and sometimes speckles on the stem develop.
Human cultivation and hybridization can also result in variegated cactus. The cross-pollination and grafting of cactus of the same species can sometimes result in this condition.
Cacti are prone to fungal disease if they are overwatered or when they have pests infestation. When this happens, the cactus will turn from being green to yellowish patches with light brown edging.
Although cacti are tough plants, they cannot escape the possibility of fungal disease. It can usually happen if they get too much water that fungi will start to breed on the moist medium. Open wounds on the cactus stem can also invite pathogens inside and infect the stem tissue.
Pests also contribute to the appearance of fungus on the cactus. Mealybugs, aphids, and scales secrete honeydew where molds begin to grow. Fungal disease can occur on any part of the cactus, and signs include brownish-yellow stems that are soft to touch.
Frost can damage the plant cells of the cacti, causing softened tissue that turns pale and yellow. It will get brown and blackish over time as it rots, making it impossible to save the affected area.
Some cacti are cold-hardy, but most species cannot endure the harsh frost and winter moisture. The ice crystals that form on the stem tissue damages the plant cells. As the ice melts, the damaged tissues become soft, pale, and purplish black.
It is paramount to assess the cause of the problem to administer the appropriate solution. Here are the viable ways to save a discolored cactus:
- Adjust light exposure,
- Change potting medium,
- Remove rotting parts,
- Get rid of pests and insects, and
- Supply adequate water.
After you have evaluated the cause of why your cactus develops a yellow tint, it’s time to find ways to prevent further damage. Yes, I’ve been there and done that many times. So I will share with you several ways how I managed to save my yellowing cactus.
If the cactus is not getting enough sunlight, it should be moved to a spot where it receives more hours of sun. Sunburned cactus should be transferred to a partially shaded area. However, the burnt portion on the epidermis will be permanent.
It is essential to adjust the amount of light the cactus receives, to avoid further sunburn or light deprivation. If you are growing your cactus indoors, the ideal location should be on the east or south-facing windowsill, where it can get at least four hours of natural light.
The best way to save your sun-damaged cactus is to reposition it to a spot with indirect but bright sunlight like the corner of your windowsill in your bedroom (where I do personally keep quite a few cacti). An area with morning sun can be a perfect new location.
A screen or shade net can be helpful to block the harmful sun rays while your cactus is enjoying the light. Below is an excellent garden screen that provides the right amount of shade.
Transfer the cactus to a well-draining, gritty cacti soil mix to avoid overwatering and root rot. It will ensure that no standing pool of water will remain on the medium and roots will grow properly.
If your cacti are growing on a poor soil type, it is time to repot them to a more suitable medium to prevent the possibility of getting yellow. You can make your DIY cacti mix that is suitable for your growing practice.
Just always bear in mind that an ideal cactus medium should drain properly, be loose, retain a bit of moisture, and contain adequate nutrients. You may also use the excellent and suitable cacti mix below.
To limit the damage of root rot, it is necessary to 1) remove the rot parts with a clean knife, ideally sterile, 2) apply cinnamon or sulfur powder on the cut to inhibit fungal growth, and 3) wait a few weeks for the wound to heal. Finally, 4) the remaining healthy part of the cacti should be replanted in fresh cacti mix with no water for 7-10 days.
Cactus will rot if overwatered, fungus-infected, dehydrated, and frost damage. The rotting area appears yellow, brown, or black and must be cut off. Not all rotten cacti are savable, and it all depends on the extent of the rot. It is best if you act quickly while the damage is not widespread.
In cases where only a small portion of the cactus is affected by rot, it is best to cut off the rotten parts to avoid more advanced decay. Once the cactus begins deteriorating, it will infect other parts rapidly.
A yellow cactus victim of pest infestation can be healed using neem oil, insecticidal soap solution, alcohol, or in more severe cases, settle on synthetic insecticides. These chemicals are sprayed on the cactus to kill off the infestation. Re-application depends on the extent of infection.
When a cactus turn yellow due to pests, it means that the infestation is widespread. Manual removal will not be effective in this situation, and it needs the application of chemicals to get rid of the insects. The table below will give you different kinds of insect buster and their application.
NOTE: Always use protective equipment and read back labels before using any kind of chemicals.
|Neem Oil||Dissolve 2 tsp of neem oil concentrate in 1 gallon of water. Spray directly on the insects during sundown. Re-apply after a week.|
|Alcohol||Make a 1:1 solution of 70% alcohol and water. Apply generously on the infected area and scrape of the insects after application. Do not spray during hot days.|
|Insecticidal Soap||Mix 2 ml of insecticidal soap in 1 liter of water and spray directly on the infestation. Use only in nighttime.|
|Permethrin Insecticide||Make 1 percent solution by mixing 1 ml with 1L of water. Spray thoroughly on the pests. Re-apply only when needed.|
I recommend these effective organic insect busters.
Repair dehydrated cactus by using deep watering or bottom watering. These techniques can help the wilted and shrunk cactus to regain and restore the lost water in their stems.
Deep watering is done by supplying water to the plant generously such that the water reaches the bottom of the pot and comes out of the drainage hole. This ensures that the entire potting medium is saturated and that all the roots, even the deep ones, can access water.
On the other hand, bottom watering is done by placing the potted cactus on a tub half-filled with water allowing it to soak for a day or two. Remove the pot after the second day and let the water drip out of the pot. In this way, the roots will have more time to take up water.
Allow the potting medium to dry out before doing these methods again until the cactus becomes plump again. Once the cactus has recovered, go back to the usual watering regime.
When a Christmas Cactus develops yellow stems, it is a sign of an underlying problem such as too much light, inadequate water, rootbound, and pests.
Christmas cactus have thin, green segmented stems and colorful flowers. They are not like any typical cactus that loves the sunny climate. They are sensitive to light, water, and soil condition. Check out the possible reason why Christmas cactus become yellow.
Prolonged direct exposure can be harmful to a Christmas Cactus. Due to its thin stems, intense sunlight can cause moisture and nutrients to evaporate easily. As a result, the stems will get droopy, yellowish, withered, and crispy. This is a typical problem in the summer season.
If this happens, remove the plant from the intense light immediately to save other stems from sun damage. Also, check the potting medium for dryness and rehydrate thoroughly if it is bone dry.
Christmas cactus loves a bit of moisture retained on its potting medium. Unlike other cactus with thick stems that can store a lot of water, Christmas cactus cannot hold as much moisture on their thin stems. Therefore, it cannot tolerate prolonged dryness and may tend to turn yellow and wilt.
Examine your cactus if it feels dry. If so, give it a good drench until the entire medium is soaking wet. Rehydrate only when the first 2 inches of the soil becomes dry.
When a Christmas cactus becomes root bound, it cannot absorb nutrients properly. Furthermore, dehydration is likely to happen due to more roots and less soil. These conditions can lead to unhealthy yellowish and withered stems.
To save your root bound Christmas cactus, re-plant it to a bigger container that can support the roots. Use a fresh cactus soil mix so the plant can absorb adequate nutrients.
Armored scales, along with other pests and sap-sucking insects, are common among Christmas cactus. They damage the plant’s tissue by sucking the juices until the stem becomes dry. It will result in discolored and wilted stems.
Get rid of the pests to save your beloved Christmas cactus. You can spray organic neem oil or insecticidal soap directly into the infestation to eliminate them.
- A cactus can get yellow due to insufficient light, poor soil type, intense light exposure, and pest infestation. Furthermore, imbalance in minerals, dehydration, fungal disease, and frost can lead to cactus discoloration. However, natural mutation can cause a cactus to become variegated.
- Generally, saving a discolored cactus can be possible by adjusting light exposure, changing the potting medium, removing rotten parts, eliminating pests, and supplying sufficient water.
- Christmas cactus will turn yellow with too much light, inadequate water, root bound, and pest infection.
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