Of course, that doesn’t mean this Brazilian succulent isn’t attractive during the rest of the year.
This plant’s flattened, segmented stems have smoother edges than its cousin, the Thanksgiving cactus (Schlumbergera truncata), and create a unique look all year.
But what happens when these evergreen “leaves” are suddenly not so green?
In most cases, the discoloration can be remedied, especially when the stems turn yellow.
Why Is My Christmas Cactus Turning Yellow?
There are five different reasons your plant’s leaves might be turning yellow.
Let’s look at each one from the most minor concern to greatest and how to check for and remedy the problem.
Poor Light Conditions
Christmas cacti are native to the Brazilian rainforests and are epiphytic succulents.
This means they store water in their stems or leaves and have evolved to grow on trees or rocks.
They’re protected from direct sunlight by the forest canopy and tend to receive dappled indirect sunlight in their natural habitat.
Even more important, succulents can be sensitive to light due to how they store water.
Too much direct light causes the plant to fade as chlorophyll deactivates in reaction.
Given enough light, the leaves may even fade from yellow to purple. More on Christmas Cactus leaves turning purple.
But the opposite is true as well.
Putting the plant in a spot with too much shade will cause it to fade to a pale yellow, as the chlorophyll can’t function properly.
The plant will become sickly and may be prone to diseases or infestation.
Treating a lighting issue is easy and, thankfully, a quick recovery time.
Have a look at your plant at various points in the day to see how bright the light is.
If there’s too much shade, simply move it to a sunnier room, ensuring the sunlight doesn’t directly hit it.
And if the room is too sunny, add a sheer curtain or move the plant away from the window.
Remember, the glass amplifies light, so south-facing windows can still get too bright even in winter.
Your Christmas cactus should recover in a few days to a week, depending on how faded it was.
Not Enough Water or Improper Watering
This is sometimes a secondary effect of too much light exposure but can also happen if you’re watering via calendar instead of when the plant’s thirsty.
Check the soil with your finger, feeling approximately ⅓ down the pot’s depth (generally 1 to 2” inches).
If the soil’s dry, your plant is thirsty.
Be sure to use room temperature distilled water (or preferably rainwater) and pour slowly and evenly around the pot until you see moisture seeping from the drainage holes.
This not only ensures the soil won’t be unevenly moist or too soggy, but it also flushes out mineral wastes that could make your plant sick over time.
Remember, you don’t look at a clock or calendar to decide when you’re thirsty, nor do plants.
You should also check the ambient humidity, adding a pebble tray or humidifier if the humidity is low.
The plant will need less frequent watering and be much happier in moderate to high humidity levels.
Plants need nutrients just like humans, and your Christmas cactus is an epiphyte, meaning it’s adapted to pulling most of its nutrition from the air and surrounding vegetation.
This isn’t exactly possible for domestic plants, so you will need to give it a balanced diluted liquid houseplant fertilizer as instructed on the package.
It’s also important to make sure you have the right soil and provide fresh soil whenever you repot the plant (which should be every 2 to 3 years).
Infestations and Disease
Your Christmas cactus can fall victim to a wide range of common household pests, such as aphids, fungus gnats, mealybugs, scale, spider mites, thrips, and whiteflies.
These pests pierce the plant’s flesh and suck its sap.
These pests also leave behind sap-heavy frass called honeydew, which can attract fungal spores, such as sooty mold.
These problems can cause discoloration to the leaves, leaving spots, streaks, or general discolorations of yellow or brown.
While usually not terminal, it’s important to get rid of these problems quickly, as they can spread to other nearby plants and will leave your plant weakened and sickly.
A neem foliar spray or soil soak will generally work wonders, although it can take a few weeks for the effects to become apparent.
You can continue using the spray every 2 weeks as a preventative or leaf shine and the soil soak every 2 to 3 weeks as a systemic insecticide and fungicide.
Too Much Water
Perhaps the single most dangerous cause of yellow leaves, overwatering can easily kill a Christmas cactus.
As mentioned, these plants are succulents, and their leaflike stems store water while the roots hate excess moisture.
It’s easy to overwater if you use a schedule instead of checking the soil to see when it needs more water.
Also, pouring too quickly or in only one spot can mean the soil fails to evenly soak up the water, creating spots of standing water that can affect the roots.
Finally, if the soil becomes too compacted from:
- Being root bound
- Not enough aggregate (such as perlite)
- Clogged drainage holes
This can leave your plant’s roots sitting in water.
Excess water leads to the dreaded root rot, which will eat away at your plant’s root system, killing it.
If your plant isn’t victim to the other four problems and the soil’s wet, you will want to repot immediately.
Check the roots and prune away any diseased ones using sterile shears, then plant in fresh soil and go easy on watering while it recovers.
You may also choose to add a bottom layer of aggregate to the pot.
You may have to try and salvage stem cuttings if the rot is too severe.