Nitrogen Toxicity in Cannabis
Too much nitrogen — easy to do during veg — causes dark green clawing leaves, burn, and delayed flowering.
What it looks like
- ●Very dark green, almost black leaves
- ●Tips clawed downward
- ●Burn at leaf tips
- ●Delayed flower onset
Quick diagnostic checks
Measure before you treat
Plant diagnostic essentials
These tools help confirm the cause of nitrogen toxicity 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 AmazonApera Instruments PH20 Meter
A more accurate, waterproof pH meter for repeatable root-zone checks.
Check price on AmazonVIVOSUN 5-Gallon Fabric Pots
Improve drainage and root-zone oxygen while reducing overwatering risk.
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Causes ranked by likelihood
1. Overfeeding veg-formula nutes
Most commonSigns
- ●Still using veg nutes into flower
- ●High-N bottle at full dose
Fix
- ✓Flush with 3x pot volume
- ✓Switch to bloom nutes (low N, higher P/K) at week 3-4 of flower
⚠️When to worry
N toxicity in flower delays harvest and reduces quality. Fix promptly.
Gear that prevents this problem
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