How to Prevent and Manage Blossom End Rot in Tomatoes and Peppers

There’s nothing quite as disheartening as watching your prized tomatoes or peppers ripen beautifully, only to discover a big, sunken, black patch where the blossom end should be. Blossom end rot is the stuff of late-summer heartbreak, and once it sets in, there’s no fixing the affected fruit. But here’s the good news: it’s totally preventable with a few simple steps.

Let’s break down what blossom end rot actually is, what causes it, and how to keep your crops healthy and rot-free.

What Is Blossom End Rot?

Blossom end rot isn’t a disease, it’s a physiological disorder caused by a calcium imbalance in the fruit during development. The plant isn’t necessarily short on calcium in the soil; it’s just struggling to get it to the fruit at the right time. The result? A dark, leathery patch forms at the blossom end of the fruit, usually the first few tomatoes or peppers to set.

How to Recognise Blossom End Rot

Keep an eye out for:

• Water-soaked spots at the blossom end of fruit
  
• Sunken, black or brown areas that grow larger over time
  
• Affected fruit often appears on the lower trusses first
  
• Tomatoes may ripen unevenly, with poor texture and taste

Once it starts, the affected fruit is a write-off but the plant itself can still bounce back with the right care.

What Causes It?

Blossom end rot is most often linked to:

• Inconsistent watering, which disrupts calcium uptake
  
• Fluctuating soil moisture: wet, then dry, then wet again
  
• Low calcium availability, especially in acidic or sandy soils
  
• Excess nitrogen fertiliser, which promotes leafy growth over fruit
  
• Rapid early growth, especially in hot spells or following heavy feeding

It’s essentially a stress response. When plants can’t move calcium efficiently, the developing fruits are the first to suffer.

How to Prevent Blossom End Rot

The key is consistency and soil health. Here’s how to prevent problems before they start:

Water Evenly and Regularly

• Deep, steady watering is essential. Aim to keep the soil evenly moist, not bone dry one day and soaked the next.
  
• In hot weather, daily checks are crucial, especially for container-grown plants.
  
• Mulch around the base of plants to help retain moisture and regulate temperature.

Improve Soil Structure

• Add plenty of organic matter like compost or well-rotted manure to improve water retention and nutrient balance.
  
• In containers, use a rich, well-balanced potting mix that holds moisture but drains well.

Avoid Overfeeding with High-Nitrogen Fertilisers

• Excess nitrogen encourages leafy growth at the expense of fruit and nutrient balance.
  
• Choose a balanced feed, or one formulated for fruiting crops (like tomato food with added calcium).

Add Calcium if Needed

If your soil is naturally low in calcium, or if you’re growing in pots, consider:

• Crushed eggshells added to the soil or compost bin
  
• Garden lime, especially in acidic soil
  
• Calcium-rich foliar sprays, though these work best as a preventative
  
• Gypsum (calcium sulphate), which won’t alter pH

Don’t Let Plants Dry Out in Pots

• Container-grown tomatoes and peppers are far more prone to blossom end rot due to erratic moisture levels.
  
• Use larger pots with added water-retaining gel or organic mulch to help stabilise moisture.

What to Do If You Spot It

If you find blossom end rot on fruit:

• Remove the affected fruit to reduce stress on the plant and encourage new, healthy growth.
  
• Check watering habits immediately and adjust if needed.
  
• Avoid panic-feeding with random fertilisers, stick to a balanced tomato or pepper feed.
  
• Add a mulch layer and consider a calcium boost if soil is suspect.

Plants can still go on to produce a healthy second flush of fruit once conditions are corrected.

Long-Term Prevention Tips

• Test soil pH annually, aim for around 6.5 for tomatoes and peppers.
  
• Feed the soil year-round with compost and slow-release organic nutrients.
  
• Rotate crops to avoid soil depletion and disease build-up.

Blossom end rot may look dramatic, but it’s not a disease, it’s a warning sign from your plants that they’re stressed and out of balance. With even watering, calcium-aware feeding, and healthy soil, it’s completely manageable. Keep your tomatoes and peppers happy, and they’ll reward you with a bountiful, unblemished harvest all season long.