悟る · diagnose & fix
Cannabis Phosphorus Deficiency
Nutrient deficiency · also: P deficiency, purple stems, dark blue green leaves
Dark blue-green leaves with purple/bronze tints and stunted growth signal low phosphorus, often triggered by cold roots.
Not sure it's phosphorus deficiency?
Snap a photo and get a free read — no signup. Satoru weighs the visual against the conditions that cause look-alikes, so you treat the real problem.
What it looks like
Older leaves darken to blue-green with purple or bronze patches; petioles/stems may redden. Spots can look bronzed or coppery. Growth and bud development slow.
Symptoms
- Dark blue-green lower leaves
- Purple/red stems and petioles
- Bronze or copper splotches
- Stunted growth, small buds
Causes
- Cold root zone (below ~15°C/60°F) cutting uptake
- pH out of range (P locks out below ~6.0 in soil)
- Genuinely low-P feed
How to fix it
- 1Warm the root zone if it's cold — often the real cause
- 2Correct pH into range
- 3Use a bloom nutrient with adequate phosphorus in flower
Prevention
- Keep root-zone temps in range
- Stable pH; bloom-appropriate feed in flower
悟る · how satoru tells it apart
Purple stems can be genetics OR cold-induced P lockout. Satoru weighs your logged temps before calling it a deficiency, so you fix the environment instead of dumping bloom nutes.
Commonly confused with: pH Lockout, Potassium Deficiency.
Not sure it's phosphorus deficiency?
Snap a photo and get a free read — no signup. Satoru weighs the visual against the conditions that cause look-alikes, so you treat the real problem.
More plant problems
Educational reference for cultivation troubleshooting. Symptoms overlap — when in doubt, match against your own conditions. Satoru fuses your photo with your logged environment for a grounded read.