Blossom End Rot: Black Bottoms on Tomatoes
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A black bottom on your tomatoes
A dark, sunken, leathery patch appears at the end of the fruit opposite the stem. Tomatoes get it most, and peppers, aubergines (eggplant) and squash-family fruit get it too.
A water problem in disguise
Calcium travels in the water a plant draws up. When watering swings between soaked and dry, too little reaches the fast-growing fruit. That is why adding calcium rarely helps: the soil usually has plenty.
The fix: steady water
- Water regularly and deeply, more often in hot spells, rather than in big irregular soakings.
- Plants in pots and grow bags dry fastest, so check them daily in summer.
- Mulch to hold moisture in the soil.
Do not give up on the plant
It often shows on the first fruits, and later fruit is usually fine once watering is steady. Pick off affected fruit and carry on. Growing guides: tomatoes and peppers.
Related problems: blight, overwatering, yellow leaves. Or go back to all garden problems.
Blossom end rot questions
Can I eat tomatoes with blossom end rot?
It is a disorder, not an infection; cut away the damaged end and the rest is usable.
Should I add calcium?
Usually not. The soil rarely lacks calcium; steady watering is the fix.
Regional notes
The problem is the same on both sides of the Atlantic; local advice and timing differ. Trusted local guides for this page:
- UK: RHS: Blossom end rot; RHS: Grow your own: August jobs. Timing in your area: the UK vegetable planting calendar.
- USA: University of Wisconsin–Madison Extension: Blossom end rot. Timing in your area: the USA vegetable planting calendar.
- Canada: Dalhousie University Faculty of Agriculture, Extended Learning: Vegetable gardening in the fall (Garden Box series). Timing in your area: the Canada vegetable planting calendar.
More problems: all garden problems.
Sources and further reading
- University of Wisconsin–Madison Extension: Blossom end rot
- RHS: Blossom end rot
- RHS: Grow your own: August jobs
- Dalhousie University Faculty of Agriculture, Extended Learning: Vegetable gardening in the fall (Garden Box series)
Facts on this page are summarised in our own words from the pages above; each is supported by at least two of them, or by one plus well-established growing science (noted in our research file). Every source was opened and checked on 23 October 2026.
Keep a garden record
Most problems come back to the same beds in the same weeks. A simple record of what grew where, and when trouble started, lets you get ahead of it next year. Sketch your beds in the free Vegetable Garden Layout Planner Tool, and keep sowing dates, problems and harvests in the Global Vegetable Garden Planner (printable PDF). Every crop we cover is in the vegetable growing guides.
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Fix The Cause, Then Plan The Next Crop
Troubleshooting works best when you improve the growing conditions and record what changed for the next season.
Keep going
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.