Cannabis Nutrient Deficiency Schedule Signs by Week

Cannabis Nutrient Deficiency Schedule Signs

Nutrient deficiency in cannabis shows up in a predictable order that tracks your feed schedule, not the calendar. Mobile nutrients such as nitrogen, phosphorus, potassium, and magnesium are pulled out of older leaves, so those turn first. Immobile nutrients such as calcium, iron, and boron cannot move, so new growth at the top distorts first. Most deficiencies trace back to a gap in the routine: a skipped feed, plain water for too long, pH drift, or salt buildup in the medium. Fix the gap and the plant usually recovers on new growth within a week.

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The sections below break the signs down by growth stage, by nutrient, and by the schedule mistakes that produce them.

Mobile nutrients: nitrogen, phosphorus, potassium, magnesium. Signs start on lower and middle leaves.
Immobile nutrients: calcium, sulfur, iron, boron, zinc, copper. Signs start on the newest leaves at the top.

Signs by Week of the Feed Schedule

Weeks 1 to 3, vegetative, nitrogen heavy: pale lower leaves with yellow moving from the tip inward points to a nitrogen short.
Weeks 4 to 6, stretch, phosphorus and potassium heavy: dull leaves, purple stems, and slow bud set point to phosphorus.
Weeks 5 to 8, flower, potassium heavy: burnt leaf edges, weak stems, and yellowing between veins with green edges point to potassium.
Weeks 8 to 10, late flower: rust spots and curling tips point to calcium or magnesium, common when feed is cut early.
Any week after a flush: top leaves turn yellow between green veins, which points to iron lockout from high pH.

How to Diagnose a Deficiency From Your Schedule

Write down the last 14 days of feeds, including what you gave, how much, and the pH of each mix.
Measure the pH and EC or PPM of the runoff before you change any bottle rate.
Locate the damaged leaves: lower foliage points to mobile nutrients, upper foliage points to immobile ones.
Match the pattern to a single nutrient using the sign list above.
Raise that one nutrient by 10 to 20 percent instead of increasing every bottle in the lineup.
Run one cycle of plain water at the correct pH, then resume the normal feed.
Photograph the plant and check again in 3 days, since new growth greens up before damaged leaves recover.

Schedule Gaps That Mimic Deficiency

Symptoms that look like a missing nutrient are often a delivery problem. Salt buildup from feeding without enough runoff drives EC up and blocks uptake. pH outside 6.0 to 6.5 in soil, or 5.5 to 6.0 in coco and hydro, locks out nutrients the plant has plenty of. Cold root zones below 65 degrees Fahrenheit slow uptake even when the mix is correct. Overwatering causes the same droop and yellowing as nitrogen shortage. Check the medium and the root zone before you add more fertilizer.

Prevention

Feed on a fixed schedule and log every mix, so a gap is easy to spot.
Water to 10 to 20 percent runoff in containers to limit salt buildup.
Calibrate your pH pen monthly, since a drifting pen causes most repeat deficiencies.
Keep the root zone between 65 and 75 degrees Fahrenheit.
Increase feed strength in small steps and watch new growth for 3 days.