Plant problems · Light, heat and air · Any stage · Act this week
Cold stress
What you see
- Leaves and stems turn purple (beyond what the strain normally shows)
- Growth slows almost to a stop
- Phosphorus and magnesium symptoms appear although the feed is right
Why it happens
Night temperatures below about 15 C or cold roots on a cold floor slow the plant and block nutrient uptake.
What to do
- Keep nights above 18 C
- Raise pots off a cold floor
- Avoid cold water
Next time
- Plan heating for autumn and winter grows
- Keep the night drop under about 8 C
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
Not sure?
Take a photo of the whole plant and a leaf stem and ask the Grow Doctor, or send it to the grow companion on Telegram.