Plant problems · Nutrients · Flowering · Act this week
Potassium deficiency
What you see
- Leaf edges and tips turn yellow, then brown and crispy, starting on older leaves
- The leaf center stays green while the edges burn
- Leaves may curl or look rusty
- Stems get weak and buds stay small
Why it happens
Potassium is mobile and in high demand in flower. Too much sodium or calcium in the water, a wrong pH or salt build up in the medium block it.
What to do
- Check pH and runoff; flush salts out with pH adjusted water if runoff is very strong
- Feed a bloom nutrient with potassium at the label dose
- Use softer or filtered water if your tap water is very hard
Next time
- Water with some runoff now and then so salts do not build up
- Use a nutrient line made for flowering
Easy to confuse with
- Phosphorus deficiency: Dark, dull or bluish green leaves with brown to purple patches, often on older leaves
- Magnesium deficiency: Yellowing between the veins of older and middle leaves while the veins stay green
- Nutrient burn: Leaf tips turn yellow, then brown and crispy, a few millimetres in
Not sure?
Take a photo of an older leaf with burnt edges, top side and underside and ask the Grow Doctor, or send it to the grow companion on Telegram.