5 Ways to Fix Blossom End Rot
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Why Your Tomatoes and Squash Are Rotting from the Bottom Up — and How to Stop It
Blossom end rot hit my garden hard the first summer I grew tomatoes in raised beds. The plants looked stunning — full of leaves and flowers — and then I spotted it: a beautiful, plump tomato with a black, sunken patch at the bottom. Then another. And another. It felt like a punch to the gut. I was doing “everything right,” or so I thought. But those early fruits were rotting before they ripened, and I had no clue why.
If you’ve been there, I get it. It’s discouraging to watch your garden work go to waste. But here’s the truth: blossom end rot isn’t a disease, and it’s not your fault. It’s a common hiccup that even experienced gardeners deal with — especially during early summer or sudden heat waves. And once you understand what’s causing it, you can fix it. That’s what this guide is for.
Whether you’re growing tomatoes in containers, peppers in a sunny bed, or zucchini along a trellis, I’ll walk you through everything you need to know to troubleshoot, prevent, and treat blossom end rot in a way that fits your garden and your season.
🍅 What Is Blossom End Rot?
Blossom end rot (often abbreviated as BER) is a calcium uptake disorder that affects developing fruits — typically in the first wave of production. It appears as a dark, sunken, leathery patch at the blossom end (the bottom) of the fruit.
Despite how alarming it looks, it’s not a disease or a pathogen. It’s a sign your plant isn’t accessing or moving enough calcium to the fruit. The kicker? There might be plenty of calcium in your soil — but your plant can’t use it properly.
💡 This is most common in:
- Tomatoes (especially paste varieties like Roma)
- Peppers (bell, banana, and hot)
- Summer squash (zucchini, yellow squash)
- Eggplants and even melons, in rare cases
🔍 How to Spot Blossom End Rot Early
Catching blossom end rot early can help you prevent further loss. Here’s what to look for:
| Crop | Early Sign | Progression | Ripening Impact |
|---|---|---|---|
| Tomato | Pale water spot at the bottom | Darkens, sinks in, leathery | Fruit stops ripening |
| Pepper | Tiny black patch, firm at first | Grows, turns mushy | Unusable but plant is healthy |
| Zucchini | Rot at flower tip | Spreads upward, fruit shrivels | Often drops off the plant |
🎯 Tip: If the rest of the plant looks great, but the bottoms of fruits are black and sunken, it’s likely BER — not pests or blight.
💡 What Causes Blossom End Rot?
Blossom end rot is a calcium delivery issue — and there are several common reasons your plant might struggle to deliver calcium to the fruit.
🛑 The Hidden Culprits:
- Inconsistent watering — drying out, then flooding
- Over-fertilizing with nitrogen — fast leafy growth but weak roots
- Low organic matter — poor nutrient and water retention
- Cool early-season soil — roots aren’t fully developed
- Soil pH imbalance or high salts — blocks calcium uptake
🧪 Curious about your soil’s pH or nutrient levels? A basic soil test kit can reveal a lot — especially if you’re growing in new or container beds.
🔗 See also: Replenishing Soil for Late Summer and Fall Planting
🩺 Will Blossom End Rot Spread or Go Away?
Here’s the encouraging part: BER often only affects the first fruits, and once your plant’s roots catch up and conditions stabilize, it tends to resolve on its own.
You do not need to pull out the plant.
👉 Just remove the affected fruit, give the plant some consistent care, and wait for the next round. Future fruits are often fine.
✅ How to Prevent and Treat Blossom End Rot
Here’s your step-by-step fix-it list. Most of these changes work quickly — you might see improvement within a week or two.
1. Water Consistently and Deeply
- Aim for even soil moisture — no wild swings
- Water deeply 2–3 times per week instead of daily sprinkles
- Use mulch to lock in moisture and reduce evaporation
- Consider drip irrigation or soaker hoses for consistent watering
🔗 Related: How to Set Up Drip Irrigation for Home Gardens
2. Go Easy on Fertilizer
- Avoid high-nitrogen fertilizers during flowering and fruiting
- Choose a balanced organic blend (e.g., 5-5-5 or 4-6-3)
- Supplement with calcium only if needed (don’t overdo it!)
3. Feed the Soil
- Add compost, worm castings, or aged manure
- These improve water retention and nutrient access
- Use mulch made from shredded leaves or straw for slow feeding
4. Use Foliar Calcium (if needed)
- Foliar sprays with calcium (like calcium chloride or calcium nitrate) can help in emergencies
- Apply in early morning; repeat weekly during fruit set
- Don’t rely on this long-term — it’s a temporary fix
5. Prune and Support Wisely
- Don’t over-prune — leaves help calcium flow
- Trellis plants like tomatoes and cucumbers to reduce stress and improve air circulation
🔗 Related: How to Trellis and Train Tomatoes to Grow Vertically
📌 Quick Reference Chart
| DO | WHY | DON’T | WHY NOT |
|---|---|---|---|
| Water evenly | Supports calcium uptake | Let soil dry out | Causes uptake failure |
| Add compost | Boosts soil health | Over-fertilize with nitrogen | Promotes imbalance |
| Use mulch | Retains moisture | Use chemical sprays during stress | Adds to root confusion |
| Remove affected fruits | Focuses plant energy on healthy growth | Leave damaged fruits | Can attract pests |
| Test soil if persistent | Understand the root cause | Assume it’s disease | BER is not infectious |
🛠️ Favorite Tools to Keep BER Away
🛒 Helpful products we’ve used in our own summer beds:
- [Soil Moisture Meter] (Affiliate) – No more guessing!
- [Organic Calcium Foliar Spray] (Affiliate) – Emergency booster
- [Soaker Hose Kit] (Affiliate) – Budget-friendly watering upgrade
- [Compost Starter or Worm Castings] (Affiliate) – Long-term soil health
🌞 Don’t Miss This Common Pitfall
A lot of gardeners panic and try to “fix” blossom end rot with powdered eggshells or crushed Tums. But these sources release calcium very slowly — too slow to fix an active issue. They’re fine for long-term soil building, but won’t stop BER in its tracks.
Stick with consistent watering, mulch, and foliar sprays for now — and focus on soil enrichment between seasons.
📋 Dealing with black-bottomed tomatoes or shriveled squash?
Download the free Blossom End Rot Troubleshooting Chart — a one-page printable that helps you identify causes, apply quick fixes, and track what’s working in your garden week by week.
Perfect for printing, taping to the shed wall, or slipping into your garden journal. 💚
🌱 Final Thoughts: You’re Not Failing — You’re Learning
Blossom end rot is a rite of passage in the summer garden. It’s frustrating, yes, but it’s also one of the easiest problems to fix once you know what’s going on. Think of it as your plant waving a flag that says, “I’m thirsty, and I’m growing too fast — help!”
So take a deep breath, water wisely, feed gently, and keep going. You’ve got this.
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