Calcium Deficiency
Irregular brown or rust-coloured spots scattered across newer leaves, often with yellow halos. New growth may be twisted, hooked or have crispy tips (a transpiration-limited form of tip burn). Calcium is immobile and moves with the transpiration stream - any condition that slows transpiration reduces uptake.
What usually causes it
- Persistently high humidity (above ~70% RH) suppressing transpiration - the dominant cause indoors
- RO / soft water with no cal-mag (especially in coco)
- pH below 5.5 in coco/hydro or below 6.2 in soil (Ca lockout)
- Cation antagonism from excess K, Mg or Na
- Overwatered, anaerobic root zone limiting uptake
Related product categories
Terms worth knowing
Walk the questions if you are not sure this is the match. The notes above are the same ones the tool ends on.