Nitrogen Deficiency in Cannabis
Nitrogen is the most-used nutrient during vegetative growth. A deficiency shows up fast: pale green, then yellow, working up from the bottom leaves.
What it looks like
- ●Lower leaves fade from green to pale to yellow
- ●Yellow works UP the plant over time
- ●Whole leaf affected, not just veins or tips
- ●Leaves eventually drop off
Quick diagnostic checks
Measure before you treat
Plant diagnostic essentials
These tools help confirm the cause of nitrogen deficiency before you change nutrients, watering, or the environment.
VIVOSUN pH and TDS Meter Combo
Check root-zone pH and nutrient strength before changing a feeding plan.
Check price on AmazonBotanicare Cal-Mag Plus
Useful when filtered water, coco, or a confirmed calcium-magnesium issue is involved.
Check price on AmazonFoxFarm Liquid Nutrient Trio
A complete, staged nutrient system for vegetative growth and flowering.
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Causes ranked by likelihood
1. Underfeeding in veg
Most commonSigns
- ●Plant is 3+ weeks old and growing fast
- ●You're not feeding or using plain water
Fix
- ✓Start feeding a veg-stage nutrient (higher N)
- ✓Week 3: ¼ strength. Week 4: ½ strength. Week 5+: full strength
Recommended products
FoxFarm Grow Big
6-4-4 — the go-to veg nitrogen feed
2. pH lockout
CommonSigns
- ●You ARE feeding but leaves are still yellow
- ●Runoff pH outside 6.0-6.8 (soil)
Fix
- ✓Measure runoff pH with a calibrated meter
- ✓Flush with pH 6.5 water to reset
⚠️When to worry
Severe N deficiency stalls growth. Left unfixed, it cuts yield 20%+. But mild fade in late flower is fine.
Gear that prevents this problem
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