Why are my camellia leaves turning yellow?

Camellias are not the cheapest of plants to purchase, in fact any specimen grown in pots larger than 10 lt can easily cost upwards of a hundred dollars! So once you have set your heart on a particular specimen, bought it home and lovingly planted it up, the last thing you want to see are its gorgeous, dark green leaves turning a rather worrying and insipid yellow colour.

Camellias are native to the acidic soils of eastern and southern Asia, and while they are more tolerant to neutral and even slightly alkaline soils than their distant cousins the Rhododendrons, they will still be adversely affected in most alkaline soils.

What is Chlorosis

Why are my camellia leaves turning yellow?
The yellowing of camellia leaves is commonly known as chlorosis, and is a commonly seen condition in acid loving plants grown in alkaline soils. Chlorosis occurs when leaves produce insufficient chlorophyll - the green colored pigmentation found in almost every single plant on the planet. The reduction in chlorophyll allows other pigments to show through - hence why the yellow carotenoid pigments now show.

Chlorosis usually occurs when there is a specific mineral deficiency in the soil, such as iron or magnesium, but in the case of camellias there may well be plenty of iron and magnesium available but the roots ability to absorb them becomes inhibited when they are subjected to a high pH.

How do you treat chlorosis

Why are my camellia leaves turning yellow?
Chlorosis can be treated by spraying the leaves with soluble iron foliar feeds every 2 - 4 weeks or more effectively by lowering the soil pH. This can be achieved by applying chelates, ferrous sulphate, aluminium sulphate, or sulphur to the soil surface and allowing them to dissolve into the soil by watering and rainfall. Of course this sounds a lot more complicated than it needs to be as water soluble, acidic plant fertilizers such as Miracid or Sequestrene can be applied as a weekly liquid feed to slowly reduce the pH and increase concentrations of the available iron and magnesium. Be aware that it will take weeks and not days for the effects to show through.

A traditional method used by Victorian plants men was to add a tablespoon of Epsom salts, dissolve it in half a gallon of water and water it in at the base of the plant. You can also apply this as a foliar spray. Victorian gardeners would also bury iron nails and other such items around the root ball before planting

How to avoid chlorosis on camellias

Camellia flowers
The simplest way to avoid chlorosis on camellias is to plant them in a suitably acidic soil.

If you are not sure of the pH of your soil then you can test it using a shop bought pH soil tester available from most large plant retailers.

Alternatively you can grow camellia in large pots using ericaceous (acidic) compost or, if you still intend planting your camellia in the ground where the soil is known to be alkaline, dig a larger hole than usual and back fill with plenty of ericaceous compost.

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