# Yellow between the veins on the newest leaves, veins green: likely causes and fixes

> Yellow between the veins on the newest leaves, veins green on cannabis is most often High root-zone pH locking out iron, manganese, zinc, boron and copper, Hard, alkaline water pushing pH up over weeks or Uncalibrated or failing pH or EC meter. How to tell them apart, the fix for each and what recov

Also called: new growth yellow with green veins, interveinal chlorosis top, yellow new leaves green veins, iron chlorosis look.

Run the checker with this sign: https://genetixbay.com/knowledge/diagnose/?at=new&s=interveinal-yellow-new

## Likely causes, most likely first

### High root-zone pH locking out iron, manganese, zinc, boron and copper (Likely)

- Kind: pH; urgency: Deal with it this week
- Fix: Bring root-zone pH into range: soil 6.2-6.8, coco and rockwool 5.8-6.2, hydro 5.5-6.2. Lower input pH by 0.2-0.3 units at a time rather than crashing it; neutralise alkaline water with a mineral acid (phosphoric, nitric or sulfuric; wear gloves and eye protection, add acid to water). Use an iron chelate stable at your pH (DTPA or EDDHA above 6.5).
- Recovery: Runoff or reservoir pH back in range at two consecutive checks; new leaves open green within 5-10 days.
- Confirm: 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.
- Confirm: Check the meters against fresh standards: Put the pH probe in fresh pH 7.0 and 4.0 buffer and the EC probe in a 1.413 mS/cm standard. If pH reads more than 0.1-0.2 off, recalibrate; if it can't be calibrated or the slope is below ~90-95%, replace the probe. Many 'lockouts' are a drifting meter.
- Confirm: Get a water report (or test your water): Ask your water utility for the annual report or test well water: alkalinity (mg/L CaCO3), pH, EC, Ca, Mg, Na, Cl, B, and whether it uses chlorine or chloramine. Alkalinity above ~100-150 mg/L as CaCO3 pushes root-zone pH up; sodium above ~50 mg/L and chloride above ~70 mg/L are a problem; softened water is high in sodium.
- Confirm: Pour-through extraction for container pH and EC: Water normally, wait 30 minutes to 2 hours, pour enough pH-adjusted water on top to collect about 50 mL of leachate (roughly 75 mL for a 15 cm pot, 150 mL for a 4 L pot, 350 mL for 11 L), and measure pH and EC of that 50 mL. Less disruptive than full runoff and more repeatable.
- Article: [pH and nutrient availability: what pH really controls, by medium](https://genetixbay.com/knowledge/ph-ec/ph-nutrient-availability.md)

### Hard, alkaline water pushing pH up over weeks (Less likely)

- Kind: Root zone; urgency: Low urgency
- Fix: Alkalinity, not water pH, drives the climb. Above about 100-150 mg/L as CaCO3 (2-3 meq/L), neutralise most of it with acid to an input pH of 5.8-6.2, or blend with RO water. Track runoff pH weekly.
- Recovery: Runoff pH stops climbing over 2-3 weeks.
- Confirm: Get a water report (or test your water): Ask your water utility for the annual report or test well water: alkalinity (mg/L CaCO3), pH, EC, Ca, Mg, Na, Cl, B, and whether it uses chlorine or chloramine. Alkalinity above ~100-150 mg/L as CaCO3 pushes root-zone pH up; sodium above ~50 mg/L and chloride above ~70 mg/L are a problem; softened water is high in sodium.
- Confirm: 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.
- Confirm: Pour-through extraction for container pH and EC: Water normally, wait 30 minutes to 2 hours, pour enough pH-adjusted water on top to collect about 50 mL of leachate (roughly 75 mL for a 15 cm pot, 150 mL for a 4 L pot, 350 mL for 11 L), and measure pH and EC of that 50 mL. Less disruptive than full runoff and more repeatable.
- Article: [Water quality for cannabis: RO vs tap, alkalinity, bicarbonates and chloramine](https://genetixbay.com/knowledge/ph-ec/water-quality.md)

### Uncalibrated or failing pH or EC meter (Less likely)

- Kind: Physical damage; urgency: Deal with it this week
- Fix: Calibrate the pH meter with fresh pH 7 then pH 4 buffer before decisions and at least weekly; store the probe wet in storage solution, never in RO water. Check EC against 1.413 mS/cm. Replace probes that won't calibrate (typical life 1-2 years). Drops and strips are too coarse to diagnose with.
- Recovery: Readings match the buffers within 0.1 pH; the 'problem' pH disappears or is confirmed.
- Confirm: Check the meters against fresh standards: Put the pH probe in fresh pH 7.0 and 4.0 buffer and the EC probe in a 1.413 mS/cm standard. If pH reads more than 0.1-0.2 off, recalibrate; if it can't be calibrated or the slope is below ~90-95%, replace the probe. Many 'lockouts' are a drifting meter.
- Article: [pH and EC meter calibration: buffers, slope, storage and when to replace a probe](https://genetixbay.com/knowledge/ph-ec/meter-calibration.md)

### Iron deficiency (usually high pH) (Less likely)

- Kind: Nutrient; urgency: Low urgency
- Fix: Bring root-zone pH into range first: soilless 5.5-6.2, soil 6.0-6.8. Neutralise alkaline water with acid. Supply 1.5-3 mg/L Fe as a chelate matched to pH: EDTA to about pH 6.5, DTPA to about 7.5, EDDHA to about 9. A foliar iron chelate spray (veg only) greens leaves in days.
- Recovery: The next new leaves open green within 5-10 days; the whitened leaves re-green partly or not at all.
- Confirm: 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.
- Confirm: Get a water report (or test your water): Ask your water utility for the annual report or test well water: alkalinity (mg/L CaCO3), pH, EC, Ca, Mg, Na, Cl, B, and whether it uses chlorine or chloramine. Alkalinity above ~100-150 mg/L as CaCO3 pushes root-zone pH up; sodium above ~50 mg/L and chloride above ~70 mg/L are a problem; softened water is high in sodium.
- Confirm: Measure PPFD at the canopy top: Use a quantum (PAR) meter, or a calibrated phone app as a rough guide, at the top leaves in a 5-9 point grid. Compare with the stage target: seedlings 100-300, veg 300-700, flower 800-1,200 µmol/m²/s at ambient CO2. Bleaching and taco at the top above ~1,100 point to light; stretch below ~300 in veg points to too little.
- Confirm: 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.
- Article: [Iron (Fe) in cannabis: yellow new growth, chelates and pH](https://genetixbay.com/knowledge/nutrients/iron.md)

### Excess phosphorus (bloom boosters) inducing Zn, Fe and Ca shortages (Less likely)

- Kind: Too much of something; urgency: Low urgency
- Fix: Drop the booster. Keep P at about 30-60 mg/L; four controlled cannabis trials found no yield or cannabinoid gain above roughly 25-60 mg/L, and excess P just leaves in the runoff.
- Recovery: New growth greens within 10 days of returning to a balanced feed.
- Confirm: 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.
- Confirm: 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.
- Article: ["Bloom boosters" for cannabis: what's real and what's marketing](https://genetixbay.com/knowledge/nutrients/bloom-boosters.md)

### Manganese deficiency (Less likely)

- Kind: Nutrient; urgency: Low urgency
- Fix: Correct high pH and alkalinity first. Supply about 0.3-0.8 mg/L Mn (manganese sulfate or chelate); avoid large iron chelate doses that compete with Mn.
- Recovery: New upper leaves lose the netted pattern within 7-10 days.
- Confirm: 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.
- Confirm: Magnifier check of leaf undersides and new growth: Use a 10-20x loupe for spider mites, thrips, aphids and whiteflies, and a 30-60x lens or clip-on phone macro for broad and russet mites. Check the undersides of 10 affected leaves across several plants and the newest shoot tips, in white light. Look for moving dots, eggs, shed skins, webbing, slender insects with black specks, and glassy specks on new growth.
- Confirm: 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.
- Article: [Manganese (Mn) in cannabis: netted chlorosis, low-pH toxicity and the iron balance](https://genetixbay.com/knowledge/nutrients/manganese.md)

### Copper toxicity (copper sprays, ionisers, pipework) (Less likely)

- Kind: Too much of something; urgency: Deal with it this week
- Fix: Stop copper fungicides and ionisers, replace copper pipework contact; change the reservoir. Keep Cu at about 0.03-0.1 mg/L.
- Recovery: New white root tips within a week.
- Confirm: 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.
- Confirm: Get a water report (or test your water): Ask your water utility for the annual report or test well water: alkalinity (mg/L CaCO3), pH, EC, Ca, Mg, Na, Cl, B, and whether it uses chlorine or chloramine. Alkalinity above ~100-150 mg/L as CaCO3 pushes root-zone pH up; sodium above ~50 mg/L and chloride above ~70 mg/L are a problem; softened water is high in sodium.
- Article: [Copper (Cu) in cannabis: limp, distorted new growth and root-burning excess](https://genetixbay.com/knowledge/nutrients/copper.md)

### Zinc toxicity (galvanised fittings, over-dosed micros) (Less likely)

- Kind: Too much of something; urgency: Low urgency
- Fix: Remove galvanised fittings from recirculating water; cap Zn near 0.1-0.5 mg/L. Excess Zn induces iron deficiency.
- Recovery: New leaves green within 10-14 days.
- Confirm: 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.
- Confirm: Get a water report (or test your water): Ask your water utility for the annual report or test well water: alkalinity (mg/L CaCO3), pH, EC, Ca, Mg, Na, Cl, B, and whether it uses chlorine or chloramine. Alkalinity above ~100-150 mg/L as CaCO3 pushes root-zone pH up; sodium above ~50 mg/L and chloride above ~70 mg/L are a problem; softened water is high in sodium.
- Article: [Zinc (Zn) in cannabis: small leaves, margin burn and the phosphorus link](https://genetixbay.com/knowledge/nutrients/zinc.md)

## Note

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.