Why Are My Citrus Leaves Curling or Turning Yellow?
Lemon and other citrus trees tell you when something is wrong — but yellowing and curling have different causes, and the wrong response can make things worse. Diagnose first, then act.
Don't Reach For A Product Yet
The most common citrus mistake we see is treating before diagnosing — grabbing a spray or a bag of fertiliser because the leaves look wrong. Misidentify the issue and you can waste a season, or do real harm: over-applying granular fertiliser, for example, can burn the roots of the tree you are trying to help.
Yellowing and curling are different signals with different causes, so start by looking properly at which you have, where on the tree it is happening, and whether anything else has changed — watering, drainage, season, or visible insects.
Yellowing Leaves: Often Nutrition
General yellowing, particularly on older leaves, often points to a nutrient issue — magnesium deficiency is a classic on citrus, showing as yellowing that leaves a green arrow or V-shape near the leaf base. Citrus are hungry trees, and Auckland's winter-wet soils do them no favours: in cold, wet soil the roots simply cannot take up nutrients well, so trees often yellow over winter and pick up again as the soil warms.
Where a deficiency is the cause, the fix is targeted feeding — not just more of everything. Identifying which nutrient is short matters, because the treatments differ.
Curling Leaves: Several Possible Causes
Curling is less specific. Sap-sucking pests like aphids curl and distort new growth; leaf miners leave silvery trails as they tunnel and pucker young leaves; water stress — too dry or too wet — curls foliage too, as can cold snaps. Each of those needs a different response, which is why curling deserves a closer inspection rather than a guess.
Check the newest growth first, and look at the undersides of curled leaves — if the cause is insects, that is usually where the evidence is.
Feeding Citrus Properly
Two principles cover most of it. First, liquid feeding acts quickly — useful when a tree needs a prompt response — while granular feeding releases slowly and needs careful dosing; the two work well combined through the growing season. Second, feed when the tree can actually use it: from spring through autumn, when the soil is warm and the roots are active, rather than in the depths of winter.
And go easy with granular fertiliser around the root zone — more is not better, and over-application is one of the most common ways citrus get damaged by their owners.
When To Get Help
If the tree is going backwards despite feeding, if the yellowing is spreading fast, or if you cannot work out what you are looking at — get another set of eyes on it before it declines further. As part of regular garden maintenance we keep an eye on fruit trees, identify what is actually wrong and put a feeding or treatment plan in place, rather than guessing.
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