Calcium Deficiency
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Fix the cause, not the leaf
No spray will help here. The trigger is soil, water supply, nutrition or temperature, so change the growing condition and judge the result on new growth, not on damaged leaves.
Not contagious
Nothing spreads from plant to plant here. Neighbouring plants showing the same signs are reacting to the same soil, water or weather, so fix the cause rather than isolating plants.
Safe to compost
No pathogen carries over on this material, so it can go on an ordinary heap with the rest of the garden waste.
When and where to look
Scout the planting in dry air below 45%.
The signs that lead here
About
Calcium is carried through a plant by the transpiration stream, so it reaches the parts that lose the most water — the leaves — and struggles to reach fruit, growing tips and hearts. Almost every case in a garden is a water-supply failure rather than a shortage of calcium in the soil.
Symptoms
Growing tips distort or die back, young leaves are small with hooked, scorched or curled edges, and hearts of lettuce and cabbage brown internally. In fruit it shows as blossom end rot in tomatoes and peppers and as bitter pit in apples.
Organic Treatment
Fix the watering before anything else: keep the soil evenly moist and mulch to stop it swinging between wet and dry. Where soil calcium really is low, apply garden lime or gypsum in autumn — gypsum where you must not raise the pH.
Chemical Treatment
Calcium nitrate feeds correct a genuine soil deficiency. Foliar calcium sprays are widely sold but do very little, because the calcium cannot move out of the sprayed leaf into the fruit that needs it.
Prevention
Water consistently, especially container plants and anything under glass. Avoid heavy potassium and magnesium feeding, which competes with calcium uptake, and keep pH above 6.0 so calcium stays available.
Related problems
Calcium Deficiency risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.