Observation and action checklist
A dark patch under a tomato: check moisture before adding calcium
Locate the damage, review root-zone conditions and choose the next observation when a tomato develops a sunken blossom-end patch.
Compare what you can see
A flattened patch is centered opposite the stem
Record whether the fruit was still enlarging. This pattern can fit blossom-end rot; compare it with the linked extension examples.
The pale patch is on the sun-facing side
Record exposed fruit and any recent leaf removal. Location matters; do not label all fruit blemishes as blossom-end rot.
Leaves, stems or many fruit surfaces are also changing
Document the wider pattern. Seek a local plant adviser if there is rapid spread or the signs do not match a simple fruit disorder.
Your next care visit
Check off what you have reviewed. Use the downloadable sheet to keep your observations.
Look at several fruit on the same plant. Note the first affected cluster, container size, drainage and recent fertilizer. Keep the plant label or packet so the record includes the actual cultivar.
Check soil moisture regularly and use mulch where suitable to reduce large swings. Avoid digging close to the roots. Base additional fertilizer on the growing medium, product instructions and a relevant soil test rather than on the fruit patch alone.
Remove affected fruit that will not develop normally, following local disposal guidance. Keep records of later fruit: a plant can produce unaffected fruit after an early affected cluster. Record changes one at a time where practical.
0 of 3 steps reviewed
Keep this in mind
Do not assume a calcium product will fix the cause. Repeated amendments without a soil or growing-medium assessment can hide the more immediate watering or root problem.
What to record next
At the next care visit, record moisture and the state of a newly developing cluster. Bring the photos, cultivar name, fertilizer details and watering history to a local adviser if the problem persists.
- Plant/cultivar and location
- Patch position relative to stem
- First affected fruit cluster and stage
- Drainage and moisture history
- Fertilizer used and any soil-test result
- Later fruit condition and changes made
References and scope
Use these extension references to compare symptoms and check crop care. Match planting advice to your variety and local growing conditions.
- University of Minnesota Extension: Tomato disorders
- University of Minnesota Extension: Tomato fruit spots
Reviewed October 20, 2026.
More care tasks
Tomato
Tomatoes splitting after rain: check the watering pattern
Compare stem-end cracks with other fruit damage, review moisture changes, and keep a short record of the next developing fruit.
Leaf lettuce
Lettuce growing a tall stalk: decide what to harvest and replace
Separate bolting from ordinary leaf growth, record the conditions, and plan a replacement batch for a more suitable growing window.