Yellow leaves

Where the yellow is tells you the cause. Old leaves, new leaves, between the veins, at the tips or near the light: start here and follow the link.

Symptoms

• Lower leaves evenly yellow: nitrogen, or normal late-flower fade.
• Yellow between the veins on old leaves: magnesium.
• Newest leaves pale with green veins: iron (high pH).
• Top leaves near the light only: light stress.
• Tips and edges yellow then brown: nutrient burn or potassium.
• Yellow speckles: spider mites.
• Yellow with wet, heavy container: over-watering.

Quick checks

• Old leaves or new leaves first?
• pH and EC of feed and run-off.
• Lift test.
• Leaf undersides with a loupe.

How to fix it

1. 1
   Check

   Check the basics first

   Check the basics first: feed and run-off pH (5.5–6.5), EC for this week, watering, climate and light.

2. 2
   Check

   Old leaves first

   Even yellow: Nitrogen deficiency. Between veins: Magnesium deficiency. Edges: Potassium deficiency.

3. 3
   Check

   New leaves first

   Pale with green veins: Iron deficiency. Only near the light: Light burn.

4. 4
   Check

   Speckles or sticky

   Speckles: Spider mite. Sticky: Aphids or Whitefly.

5. 5
   Monitor

   Change one thing at a time

   Give it 3–5 days and judge the new growth.

Likely causes

• pH out of range (the most common cause).
• Feed too weak or too strong.
• Over-watering or cold roots.
• Light too close.
• Pests.
• Natural fade late in flower.

What to avoid

• Don't panic-feed.
• Don't worry about the oldest leaves fading in the last weeks of flower.

Prevention

• Weekly pH and EC checks.
• Calibrated meters.
• Water by weight.

Monkey products that can help

Mag Cal

If you're in coco or on soft or RO water and the yellowing is between the veins of older leaves.

1 ml per litre (10 ml per 10 L), for coco and for soft or RO water.

View product →

Products support a healthy plant. They don't replace fixing the cause.

When to get help

If yellowing spreads with all basics in range, email info@monkeynutrients.co.uk with photos, readings, medium and week.

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