Blossom End Rot
Disease · Commonly affects: tomatoes, cherry tomatoes, beefsteak tomatoes, sweet peppers, chilli peppers, aubergines
Blossom end rot is a physiological disorder rather than an infection. It happens when developing fruit cannot receive calcium steadily, usually because watering has been irregular. It is common on tomatoes and peppers grown in pots, grow bags or greenhouse borders during warm UK weather. The damaged fruit will not recover, but later fruit can be protected.
How to identify it
A water-soaked, pale brown mark develops at the blossom end, opposite the stalk. It usually starts as a patch about 5-15 mm wide and enlarges into a dark brown or black, sunken, leathery area. The rest of the fruit may look healthy. It is most often seen on green, developing tomatoes and peppers. Unlike blight, there is no white mould beneath leaf patches and foliage usually remains normal.
Damage
The affected end of the fruit becomes tough, dry and unappetising, so the fruit should not be eaten. Secondary rots may enter the damaged patch, causing it to soften. Repeated losses can substantially reduce the usable tomato or pepper crop, especially on the first trusses. It is frustrating, but it does not spread directly from fruit to fruit.
Prevention
Keep compost and soil consistently moist from planting until the final harvest. Water thoroughly whenever the surface begins to dry, rather than allowing pots or grow bags to become very dry and then soaking them. Use generously sized containers with drainage holes and mulch the surface to slow evaporation. Avoid damaging roots when planting or hoeing. Feed and water steadily, and choose varieties suited to container growing where possible.
How to manage it
Remove affected fruit so the plant can direct energy towards healthy new growth. Establish a regular watering routine, checking containers daily in warm or windy weather and ensuring excess water can drain away. Add a mulch of compost or other organic material around plants, keeping it clear of stems. Avoid sudden changes in watering or root disturbance. Harvest sound fruit as it ripens, and monitor new fruit for improvement.
Blossom End Rot: frequently asked questions
How do I identify blossom end rot?
A water-soaked, pale brown mark develops at the blossom end, opposite the stalk.
How do I prevent blossom end rot?
Keep compost and soil consistently moist from planting until the final harvest.
How do I get rid of blossom end rot?
Remove affected fruit so the plant can direct energy towards healthy new growth.
General guidance for UK home gardens and allotments, focused on prevention and non-chemical control. For a confirmed diagnosis, the RHS or a local garden centre can help. Page updated 19 Sep 2026.