Advice
Camellia leaf yellowing
Although camellias are an evergreen plant a percentage of older (often lower) leaves will yellow and fall naturally throughout the year. Additionally camellias, like many evergreens, often look pale or 'chlorotic' early on in the year before the soil warms up. This problem usually rectifies itself as the season progresses.
If
leaf yellowing is excessive however then waterlogging may
be the cause. Waterlogging limits or even stops root function,
the damaged roots subsequently rotting off. This has a subsequent
effect on the plant's foliage as water and nutrient uptake
is insufficient. If this is thought likely then a root examination
would be useful. Waterlogged roots would be rotten and discoloured,
whereas healthy roots would be firm and have a creamy-white
center. Plants grown in pots are especially susceptible, and
should be stood on pot 'feet' during the winter months. Pot-grown
plants should have rotten roots pruned out and be re-potted
using fresh compost. Plants in the soil should be moved to
a better drained site, or be re-planted after drainage improvements
are made to the soil (e.g. the incorporation of grit or composted
bark).
Being ericaceous plants, camellias have specific soil and nutrient requirements. Plants grown in soils with a pH of 6.5 or over often show signs of chlorosis. As with all plants regular feeding (following the manufacturer's instructions) should be carried out to ensure that the plants do not become deficient in a particular nutrient. Bear in mind that camellias require an ericaceous fertilizer. Mild cases of chlorosis can usually be cured using a chelated iron product, but in severe cases replanting into an acid soil or ericaceous compost is required.