Camellia’s produce beautiful flowers and make great hedge plants. Typically they have shiny dark green leaves but at times they can be discolored. This is caused for a range of reasons so today I will explain what causes this to happen and how to stop this from occurring.
Overwatering, high soil pH, and underwatering cause camellia leaves to turn yellow. To fix yellow leaves change the pH so that it is 6.0 to 6.5, remedy pests and diseases with neem oil, and water Camellia once a week.
Overwatering causes camellia leaves to turn yellow
Giving camellias too much water causes the soil to remain wet for prolonged periods of time. When this happens the roots become waterlogged. This causes them to become soggy and much softer. As a result, they can’t uptake water and nutrient as well. This causes camellias to become nutrient deficient and yellowing of the leaves the plant’s way of telling you.
Although, there are a few reasons why the leaves turn yellow, make sure you’re only watering them when they need it. It’s fairly simple to tell when they need water, and when you should let them do their thing. Here are some rules of thumb, for when to know when they should be watered.
- Only water them when you feel the top inch (2.5 cm) of the soil is completely dry.
- Unless you’ve had a period of prolonged rain, water them about once every 1 to 2 weeks.
The pH of the soil is how acidic or alkaline it is. As you may remember from high school chemistry a lower pH number is more acidic, and a higher number is more alkaline – sometimes called more basic.
When the soil is more acidic it breaks down nutrients. And causes the soil environment to have certain nutrients such as iron to be more available for the camellias to absorb and use. Camellias in general need a more acidic environment than other plants.
The symptoms of the wrong pH are easier to spot than others. When the pH is wrong the new growth exhibits yellowing. But, the older leaves closer to the base of the stem are dark green.
To be sure this is the issue get an inexpensive pH soil testing kit from your garden supply store and test the soil. The ideal pH is 6.0 to 6.5.
It generally takes a long time to change the pH by adding nutrients to the top of the soil. Therefore, if it’s an issue then you should consider preparing a new soil that is the right pH and replant the camellia plant into it. If it’s very established and therefore very difficult to dig out you can add an iron mix powder from the garden supply and follow the instructions.
- For soil with a pH that is too high – above 6.5 then add sulfur and/or organic material.
- For soil that is too acidic (pH lower than 6.0) add limestone-based powders, which are commonly called lime.
Pests that suck the nutrients out of the plant
There are various pest insects such as scale, and mealybugs that latch onto plants. Camellias can suffer from an infestation that typically isn’t spotted until the leaves begin turning yellow. It’s different from other forms of yellowing as it creates yellow spots. And larger dense patches of yellow spots.
Underneath the leaves, you can see what looks like spider webs but much are smaller. With tiny bugs scattered throughout. There can also be small bumps on stems which are the bugs that have latched on and will remain there for their life cycle feeding on the plant. Luckily they are very easy to get rid of once you identify that it’s pest insects that are causing it.
The affected leaves won’t return to normal, but any new growth will remain perfectly green, and undamaged provided they don’t suffer from another infestation.
- Spray a neem oil and water mixture on them after sunset completely covering the affected areas.
- Isopropyl alcohol (methylated spirits) can also be dabbed onto them using a cotton bud, or piece of cotton wool.
- An insecticide from a garden supply store can also be sprayed on them.
Diseases such as fungus
There are various fungal diseases that can begin to grow when they settle on the plant. These molds feed on the juices of the leaves as they grow and cause the leaves the turn yellow. This is easy to identify as the yellowing will be accompanied by black spots, or there will be white or green mold growing on the surface of the leaves.
This can also be easily remedied, the damaged leaves won’t return to normal. It’s common to thin out and shape camellias by pruning. In so doing you can decide to preferentially prune more from the stems that have leaves that have been damaged.
Before, the new fresh undamaged grows in. And fingers crossed fungus spores don’t make their way onto the leaves again.
- Spray the affected areas with a cooper-based fungicide to kill the mold to stop it from spreading.
- Prune as many of the damaged leaves without thinning out the plant too much.
The quality of the soil affects how much water remains in the soil. Thick clayey soil makes it difficult for water to soak into the soil and get down into the roots. Once the water gets down into the soil it stays in the soil and can cause the roots to become damaged.
Although you might be getting enough rain or watering them regularly your camellias can be effectively underwatered. Also, if you’ve had a week or two of no rain and haven’t watered them yourself they can need more water and this will begin to show as yellowing of the leaves.
If you’ve planted camellias into clayey or sandy soil the main solution is to dig them out, dig a much deeper hole, and fill it will high quality soil like a bag of compost from the garden supply store. However, this is quite a big job.
If you apply a thick layer (1 foot) of bark, and wood chips to the base of the plant the nutrients will eventually seep into the soil and transform it so that it is dark, loose, and free draining. But, this can take a year or so.
- Feel the top inch (2.5 cm) of the soil and if it’s bone dry then water them.
- Replant the camellias into a hole filled with compost.
- Apply a thick layer of mulch at the base of the tree to slowly improve the quality of the soil.
Not enough nutrients or over-fertilizing
When the soil is devoid of nutrients the leaves can exhibit yellowing. This is different from other forms of yellowing because generally the veins in the leaves will be green but the rest of each of the leaves will be yellow. It has a scientific term known as chlorosis which is where a plant isn’t absorbing enough nutrients.
It can also be brought on by over-fertilizing which damages the roots and reduces their ability to absorb nutrients. So, it’s difficult to know if you’re giving them too many nutrients or not enough based on the yellowing itself.
- Use a specially formulated camellia fertilizer and follow the manufacturer’s recommendations.
- Monitor the new growth for more or less yellowing of the leaves and adjust the amount of fertilizer as necessary.