Blossom End Rot

At some point, every tomato grower will face blossom end rot (BER). I used to think it was just about calcium, or maybe a fluke. I’d treat the soil, add what I thought was missing, and yet... that dreaded black patch still showed up.

It wasn’t until I followed Craig LeHoullier’s advice author of “Epic Tomatoes: How to Select & Grow the Best Varities of All Time”, that things finally started making sense.

Now? I still get the odd one here and there (it’s normal), but I know how to keep it minimal, and most importantly, I understand why it happens. And I've stopped beating myself up about it.

San Marzano & other Roma/plum types

These beauties are naturally more prone to blossom end rot, it’s written into their genetics. Paste varieties, like San Marzano and Roma, tend to be more sensitive during fruit development.

Heat waves, dry spells, and even inconsistent watering can interrupt calcium flow, and that’s when BER sets in.

Don’t be surprised if they’re the first to show symptoms, they’re just a little more dramatic under stress.

Craig points out something important:

If your soil is too acidic, especially when mulching heavily with things like peat moss, it can make your soil too acidic and lock up calcium. So even if the nutrients are there, your plants can’t use them.

That’s why Craig recommends building your soil from the bottom up. He suggests layering:

• Compost
• Leaves
• Manure and straw
• Blood and bone
• Then lime if your soil is on the acidic side

By prepping this way before planting, your tomatoes get everything they need from the start. Remember failing to plan is planning to fail, so hop to it, springs just around the corner, get those beds mulched and the magic working.

Craig also explains (page 185 of Epic Tomatoes) that blossom end rot can simply be a physiological issue related to how the fruit is ripening. In other words: don’t beat yourself up. Sometimes, it’s just the plant doing its thing.

For years, I focused only on the soil pH. It turns out, that’s just one piece of the puzzle. Once I learned to look at all the contributing factors, soil structure, watering rhythm, weather, and variety, everything changed.

Now, if I spot blossom end rot on an early fruit? I just remove it, I don't let the plant waste any energy on developing poor fruit and I move on. The rest usually grow perfectly.

1. Know Your Varieties
Some are just more vulnerable. Roma-style tomatoes are BER magnets. If you’ve struggled with BER in certain varieties year after year, consider letting them go and trying more resilient ones.

2. Understand Environmental Triggers
Things like drought, uneven watering, excess nitrogen, or cold nights can mess with calcium uptake. It’s not just about the

3. Test & Tweak Your Soil
Aim for a pH between 6.2 and 6.8. If it's too low, add lime. A simple soil test can save a lot of heartache. Without it fruit development stalls and rot creeps in.

4. Mulch Generously

Mulch around the base of your plants to lock in soil moisture and buffer against wild swings in temperature and hydration. Just avoid mulch types that increase soil acidity (like peat-based ones).

5. Water Deeply Especially in the Heat

Hot spells can dry out soil quickly and interrupt calcium flow inside the plant. Keep your watering consistent — especially during flowering and early fruit set.

“When you learn teach, when you get give.”

— Maya Angelo