How do you treat yellow leaves on Camellias?

If you look over at the various front gardens of suburbia, you can be forgive for thinking that Camellias are a lovely mid-green colour, often attractively patterned with yellow markings. However the reality is that Camellias should be a glossy dark-green and the reason they are often not this hue is due to their ericaceous nature! So if they are not supposed to be yellow, how do you treat yellow leaves on Camellias?

Camellias are lime intolerant. If they are planted in soil which has a component of lime to it (making the soil alkaline in nature) camellias struggle in their ability to uptake the nutrients iron, magnesium and zinc. This is called chlorosis and it is identified by the leaves turning yellow in a characteristic manner.

Iron deficiency is by far the most common cause of chlorosis and is identified with yellowings on the younger or terminal leaves and later works inward to the older leaves. Conversely, Manganese and zinc deficiencies develop on the inner or the older leaves first and then progress outward.

Iron is essential for the production of the green chlorophyll pigment and so without iron, there is no green pigment and that is why you are left with the underlying yellow carotenoid pigments showing through instead. There are of course other reasons why iron uptake is prevented such as high levels of copper in the soil but for the benefit of tis articles we will concentrate on the most likely causes which is the increasing insolubility of iron in alkaline soils.

One of the easiest treatments is to plant your camellia into ericaceous compost smaller plants can be dug out and replanted in it, while container grown plants can be potted on into their next sized pot with it.

With regards to established garden plants treatment of yellow leaves on Camellias can be dealt with in a number of ways such as digging sulfur (often sold in garden centres as flowers of sulphur and always use the recommended doses) or moss peat in around the root system, while trying not to damage the roots themselves. Moss peat is naturally acidic and will therefore acidify the surrounding soil. Be aware that sedge peat can be acidic or alkaline and so unless you have checked its pH first it is not recommended to be used for soil acidification.

One simple method to treat yellow leaves on Camellias is to regularly apply a liquid soluble ericaceous fertiliser. Over time this will help to increase the acidity  around the root ball, allowing the plant t take up the available iron.

The last best option is an application of chelated iron. Ths is iron combined with an organic chemical (called a chelate) that helps keep it in a plant-available form. Always apply using recommended dose rates, but be aware that this treatment may need to be repeated several times during the growing season.

If all else fails, one last option is to spray iron sulphate (otherwise known as ferrous sulphate) directly onto the plant leaves as a rate of 1 to 2 oz of ferrous sulfate per gallon of water.

No comments: