Red-purple petioles with yellowing lower leaves
Red-brown petioles appear on the worst-affected lower leaves as they yellow..
- Also called
- red stems and yellow leaves
- purple petioles lower leaves yellow
Likely causes, most likely first
Ranked for this sign on its own. Your stage, medium and readings change the order, so run the checker for your plant.
LikelyNitrogen deficiency
Fix: Fix roots, watering and pH first. If N is genuinely short, raise feed N by about 10-20% (not double): mineral feeds around 150-200 mg/L N in veg and early flower; one DWC flowering trial predicted a yield optimum near 194 mg/L. Coco/hydro: raise base feed EC by ~0.2 mS/cm. Soil: liquid feed at label rate. Living soil: top-dress a fast organic N source and allow 1-2 weeks. Late flower: a gradual fade is the planned N taper, not a fault.
Recovery: Yellowing stops climbing within 5-7 days and new leaves emerge mid-green; already-yellow leaves do not recover. Runoff EC climbs back toward input.
How to confirm it
- Measure runoff EC against input EC. Water to 10-20% runoff, collect the runoff in a clean cup and measure EC of both with a calibrated meter (1.413 mS/cm standard). Runoff more than ~0.5 mS/cm above input means salt build-up; well below input means the plant is hungry or you are over-leaching. In hydro, compare reservoir EC with the EC you mixed.
- Measure input pH and root-zone (runoff or reservoir) pH. Calibrate the meter with fresh pH 7 and pH 4 buffers, then measure the mixed feed and the runoff (containers) or reservoir (hydro). Soil and living soil should sit at 6.0-7.0, coco, rockwool and peat mixes at 5.5-6.5, hydro at 5.5-6.2. Track 3+ readings; one reading is not a trend.
- Look at the roots. Hydro: lift the net pot and look at the root mass in good white light. Containers: tip the plant out with a hand over the medium and look at the edges and bottom of the root ball. Healthy roots are white to cream with fine fuzzy tips. Brown roots whose outer layer slides off between the fingers leave a bare thread: rot. Firm, evenly tan roots with white tips in coloured solution are staining.
- Watch new growth for 5-10 days after one change. Make one correction at a time, mark the top node with a twist tie and photograph the same leaves every 2-3 days. Damaged leaves never recover; judge only new growth and whether the symptom stops spreading. Mobile-nutrient symptoms stop climbing within 5-7 days; immobile ones show in new leaves within 7-10 days.
- Leaf tissue analysis. Send 20-30 most-recently-matured leaves (no petioles) from affected plants, and separately from healthy ones, to an agricultural lab. Compare with cannabis and hemp sufficiency ranges (for example N 3.3-4.8%, Mg 0.40-0.81%, K 1.8-2.9% dry weight in recent mature leaves). Results take 1-2 weeks; use it to confirm a chronic problem, not an emergency.
PossibleNormal late-flower fade (senescence)
Fix: Nothing to fix in the last 2-3 weeks of flower. Keep feeding at stage strength with N tapered; don't 'flush' (pre-harvest flushing starves the plant while it packs on final weight and resin, and controlled studies show no quality gain). Fade before week 5-6 of flower suggests N was cut too early.
Recovery: Buds keep swelling and ripening normally while fan leaves fade.
How to confirm it
- Measure runoff EC against input EC. Water to 10-20% runoff, collect the runoff in a clean cup and measure EC of both with a calibrated meter (1.413 mS/cm standard). Runoff more than ~0.5 mS/cm above input means salt build-up; well below input means the plant is hungry or you are over-leaching. In hydro, compare reservoir EC with the EC you mixed.
Look for
Lower fan leaves yellowing with red-brown petioles; upper leaves green with green petioles..
The full guide: Nitrogen (N) in cannabis: nitrate vs ammonium, deficiency, toxicity and targets
Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.
