Question: The leaves of my plant have gone yellow. What has caused this?
This symptom can have many different causes. Root problems can again be responsible, but if the yellowing is confined to the areas between the veins, then the problem is most likely to be a nutrient deficiency. Being ericaceous (acid-loving) plants, camellias can suffer from iron and manganese deficiencies if the soil or growing medium is too alkaline. In gardens with alkaline soils they are best grown in containers using an ericaceous compost. Use acidic fertilisers, and avoid prolonged watering with tap water if you are in a hard water area. Chelated iron and other trace elements will allow camellia to take up To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key plant nutrients usually derived from soil are nitrogen, phosphorus and potassium, while carbon, oxygen and hydrogen are absorbed from the air. Other vital soil nutrients include magnesium, calcium and sulphur. Most garden soils contain enough nutrients to promote healthy plant growth.
nutrients in alkaline soils although effective chelated fertilisers are expensive and annual treatments are needed. 'Sequestrene' is a common trade name for chelated fertiliser.
Irregular yellow or creamy-white blotches on the leaves may be the result of virus infection. Plants showing these leaf symptoms usually still grow and flower well.
Although they are evergreen plants, camellias still periodically shed their old leaves. Don’t worry about leaves turning yellow and falling in spring or summer if this is confined to old leaves near the base and within the plant.
Question: Some of the leaves of my plant have turned brown. What is the problem?
Again, there can be a number of causes for this, such as a root problem, drought, frost damage or strong winds. Affected leaves may be shed.
If the browning takes the form of spots or blotches, then it is possible that the plant has become infected with one of the leaf blight fungi. It is sometimes possible to see small, black, fruiting bodies of the causal fungus within the affected area. In severe cases the pathogen can progress into the branch to cause dieback.
After a heat wave, camellia leaves often develop large brown 'burnt' blotches on leaves as a result of high temperature damage.
Question: Many of the leaves of my camellia have a thick, black growth on the surface. What has caused this?
The black growth is that of a sooty mould fungus. This grows on the sugary honeydew excreted by sap-sucking insects, and on camellia the usual source of the honeydew is an infestation by cushion scale. Check the underside of the leaves for small, light brown scales, often with an elongate white egg sac. Sooty mould is not directly harmful to the plant and can be washed from the leaves, but if the insect remains active the growth will reappear.
Question: My plant looks healthy apart from one or two leaves, which became very swollen and have now turned white. Is this a significant problem?
Your plant is affected by a fungal disease called camellia gall. Whilst unsightly, this is not a serious problem. Affected parts can be picked off, ideally before the white bloom of fungal spores is produced.
Question: The leaves of my camellia have raised corky spots and patches underneath. What has caused this?
It sounds as though the leaves could be affected by oedema. This is a physiological problem, caused when the plant takes up more water through its roots that it can lose readily through the leaves. Overwatering or waterlogging can be to blame, and camellias grown in polytunnels or under glass where The concentration of water vapour in the atmosphere. This affects the rate at which plants transpire (lose water from their leaf pores), which in turn affects how much water their roots absorb from the soil. If air humidity is low, plants transpire quickly and become at risk of wilting if water is lost from the leaves faster than it can be absorbed by the roots. Different plants require different levels of humidity to thrive. Many tropical houseplants need high humidity and are best grown in a steamy bathroom, misted regularly or placed on a saucer of damp pebbles. In a greenhouse, humidity can be raised in hot weather by damping down (wetting) the floor or overhead misting.
humidity is high can also develop symptoms.