Common crops affected
What is it?
Blossom-end rot is a physiological disorder caused by a calcium deficiency in the developing fruit. Often there is enough calcium in the soil, but the plant cannot move it into the fruit fast enough — usually because of inconsistent watering, rapid growth, or root stress that disrupts calcium uptake and transport. It is not contagious and is not caused by a pathogen.
How to identify it
- A water-soaked spot at the blossom (bottom) end of young fruit
- The spot enlarges into a sunken, dark brown to black, leathery patch
- Affects the fruit, not the leaves; first fruits of the season are common victims
- Often follows irregular watering, drought, or heat stress
Damage and how it spreads
Affected fruit is unmarketable and usually can't be salvaged, and a bad run early in the season can cost a meaningful share of the first harvest. Because the cause is calcium movement rather than infection, the fix is about correcting calcium availability and stabilizing growing conditions — not spraying a fungicide or insecticide.
How to control it
- Keep soil moisture even — mulch and water consistently to avoid drought-then-flood swings.
- Avoid over-fertilizing with high-nitrogen feeds that push fast growth and dilute calcium.
- Correct calcium availability at the root zone and support uptake into the fruit.
- Remove affected fruit so the plant directs resources to healthy fruit.
Recommended Vegalab solution: Calcium Boost
Vegalab Calcium Boost is an advanced soluble calcium supplement that makes calcium readily available to the plant to correct and prevent blossom-end rot. Pair it with Cellular Boost, which supports cell integrity and helps prevent drought-induced disorders in fruit. Apply per label alongside consistent watering.
| Role | Product | Use |
|---|---|---|
| Primary correction | Calcium Boost | Soluble calcium correction |
| Companion / broader pressure | Cellular Boost | Cell integrity / anti-cracking |
Preventing it next season
The most reliable prevention is steady soil moisture plus available calcium from early fruit set. Mulch, water evenly, avoid nitrogen spikes, and maintain calcium with Calcium Boost through the fruiting period. Strong roots improve uptake — support them with Root Boost.
Claims and product availability vary by jurisdiction. Always read and follow the product label.