Plant problems · Nutrients · Any stage · Act this week
Nitrogen deficiency
What you see
- Lower, older leaves turn pale green, then evenly yellow from the tip inwards
- Yellowing climbs up the plant week by week while the top stays green
- Yellow leaves go soft and drop off on their own
- Growth slows and new leaves come in smaller
Why it happens
Nitrogen is mobile: when the plant runs short it pulls nitrogen out of old leaves to feed new growth. Common causes are a medium that has run out of food, a pH outside the range where nitrogen is taken up, or overwatering that keeps roots from feeding. Some yellowing of the lowest leaves in late flower is normal.
What to do
- Check the pH of what goes in and what runs out (soil 6.0 to 7.0, coco and hydro 5.5 to 6.5)
- In veg, feed a grow nutrient with more nitrogen at the dose on the label, or top dress soil with a nitrogen rich amendment
- Remove leaves that are fully yellow only when they come off with a light pull
- Expect the yellowing to stop spreading within a week; leaves that are already yellow will not turn green again
Next time
- Repot or feed before the medium is exhausted, especially in small pots
- Keep a simple feed and pH log so you see the trend early
Easy to confuse with
- Magnesium deficiency: Yellowing between the veins of older and middle leaves while the veins stay green
- pH lockout: Several deficiencies at once: yellowing, spots and burnt edges together
- Overwatering: The whole plant droops with leaves that feel firm and swollen, not limp
Not sure?
Take a photo of a whole branch from the bottom of the plant up, in daylight and ask the Grow Doctor, or send it to the grow companion on Telegram.