leaves look burnt on healthy plant

eviecordeliaMay 18, 2007

I have a new azalea, a lot of the leaves have either got a deep red/rust colour around the edges - or are turning dark brown and very dry and curling inwards (looks almost like they are burnt) it starts at the tips till it affects the whole leaf and underneath it is a lighter brown colour if i look very close there seems to be black/grey patches, maybe mould - what is this and what should i do to save my plant?

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rhodyman(SE PA, USDA Z6)

You gave a perfect description of frost damage except for the fact that it keeps progressing.

I am guessing your problem is a potassium and/or iron deficiency. Potassium & Iron: Potassium deficiency can be difficult to diagnose. A plant must have sufficient iron to utilize available potassium. For this reason the symptoms of potassium and iron deficiency are almost identical in the initial stages. Potassium deficiency begins with leaf yellowing, which eventually spreads between the veins. Leaf tips and margins show scorch and necrosis. If the soil is not acidic enough, this will cause an iron deficiency and the same symptoms.

Yellowing of a leaf between dark green veins is called chlorosis and is usually caused by an iron deficiency. Many conditions can be responsible for an iron deficiency. Poor drainage, planting too deeply, heavy soil with poor aeration, insect or fungus damage in the root zone and lack of moisture all induce chlorosis. After these conditions are eliminated as possible causes, soil testing is in order. Chlorosis can be caused by malnutrition caused by alkalinity of the soil, potassium deficiency, calcium deficiency, iron deficiency or magnesium deficiency. Iron is most readily available in acidic soils between pH 4.5-6.0. When the soil pH is above 6.5, iron may be present in adequate amounts, but is in an unusable form, due to an excessive amount of calcium carbonate. This can occur when plants are placed too close to cement foundations or walkways. Soil amendments that acidify the soil, such as iron sulfate or sulfur, are the best long term solution. Foliar sprays of iron sulfate or chelated iron can reduce symptoms. A combination of acidification with sulfur and iron supplements such as chelated iron or iron sulfate will usually treat this problem. Chlorosis caused by magnesium deficiency is initially the same as iron, but progresses to form reddish purple blotches and marginal leaf necrosis (browning of leaf edges). Epsom salts are a good source of supplemental magnesium. Chlorosis can also be caused by nitrogen toxicity (usually caused by nitrate fertilizers) or other conditions that damage the roots such as root rot, severe cutting of the roots, root weevils or root death caused by extreme amounts of fertilizer.

    Bookmark   May 18, 2007 at 8:13AM
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