Yellowing leaves reveal nutrient deficiency in plants
I like coloured foliage in the garden but this does not include the yellowing leaves of plants that are struggling to take up the nutrients they need.
This often occurs with plants in containers, some grafted plants, and those grown outside of the soil pH they prefer.
The first sign of nutrient deficiency is retarded growth.
Leaves are often yellow, or yellow with green veins, but can have red or purple mottling or look scorched.
The best advice is to grow plants naturally suited to your soils.
If, like me, you fail to listen to this advice, mulch distressed plants with compost and provide nutrients by spraying foliage with a trace elements solution.
You can buy individual trace elements but I prefer the “complete” trace elements mix because without a chemical analysis of the leaves you can only make an educated guess about the deficiency.
All fruit trees should be sprayed with this twice yearly. Follow up with a foliar feed of a liquid fertiliser containing fish, seaweed and compost.
Plants whose natural habitat is acid soils, like gardenias, azaleas and camellias, are unable to get enough iron from my alkaline sands and their deficiency shows up as yellow leaves with green veins.
Sometimes it’s so bad the young leaves are totally yellow or white.
To fix this you can spray foliage with iron chelates but this lasts only for a few weeks, so last weekend I made iron compost.
Mix one cup of iron sulphate (wear old clothes as it stains) into 10 litres of moist compost or animal manure.
Dig holes about 20cm deep into the root zone of plants — about three holes for a rosebush and more for bigger plants.
Compact the organic matter into the holes and water.
This will work for several years unless your irrigation water is very alkaline.
A yellowing gardenia leaf shows the signs of nutrient deficiency.