Plant Doctor Archive

Yellow leaves on citrus

THE leaves of my potted lemon tree are yellowing. What do you think could be causing this?

YELLOWING of citrus trees is often caused by lack of water, a general lack of nutrients or sometimes, more specifically, magnesium deficiency.

For a lemon tree in a pot, the best approach is to feed regularly with a liquid fertiliser such as Thrive or Nitrosol throughout the growing season and in both spring and autumn feed with a slow release fertiliser such as Osmocote or Plantacote. Sprinkle the fertiliser granules on to the surface of the mix or poke holes with a stick into the mix and pour a few granules into each hole.

Just in case magnesium deficiency is the problem, you could try spraying with a solution of magnesium sulphate (Epsom salts). Dissolve 20g in a litre of water, add a drop of dishwashing liquid and spray all the foliage.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.