Blossom End Rot Won’t Take My Tomatoes

Last July I pulled back a tomato plant to check on my first real fruits of the season and found the bottoms rotted out, black and sunken like something had given up on them from the inside. I had four plants. Three of them hit. Three.

Blossom end rot is not a disease. That’s the thing that gets people. No fungus, no pest, nothing to spray. It’s a calcium uptake problem, usually caused by inconsistent watering messing with how the plant moves nutrients around. Which, now that I think about it, is kind of rude. The tomato had the calcium. It just couldn’t get it where it needed to go.

Anyway. Here’s what I do now, and none of it costs much.

Water Consistently. Boring but True.

The number one fix is the free one, which should have been my first clue. Inconsistent watering, soaking the plant one day and ignoring it for four days while it bakes, that’s the main trigger. Roots under stress can’t move calcium efficiently. So the rot shows up even when your soil has plenty of calcium already.

I water deeply every other day during dry stretches in summer. Not a quick sprinkle. Actual water getting down 6 to 8 inches. A $3.97 soil moisture meter from the dollar bins at Fred Meyer taught me I was watering way less than I thought. Worth every penny of that $3.97.

Mulch helps a lot here too. A couple inches of straw or wood chips around the base slows down that wet-dry cycle that causes the problem in the first place. I use whatever’s cheap. Last year I grabbed a bale of straw from Bi-Mart for $6.29 and it covered four raised beds with some left over for my daughters to throw at each other.

Tums. Yes, Tums.

This is the one people look at me weird for. Tums are calcium carbonate. That’s it. The generic store brand antacid tablets from Walgreens, the big bottle of 150 for $4.49, are literally a calcium amendment. I drop two or three crushed tablets into the planting hole when I transplant, and then once or twice more during the season scratched into the soil at the base.

Does it work? My last two seasons have been basically rot-free. Could be the mulch, could be the watering, could be the Tums. Probably all three. But the Tums cost almost nothing and I felt like a genius doing it, which frankly has a value of its own.

You can also use garden lime worked into the soil before planting if your pH is low. Zone 8b PNW soils run acidic from all the rain, so this actually makes sense here. I got a 5-pound bag for $4.89 and used about a quarter of it across my tomato bed.

Epsom Salt Is Not the Answer Here

I have to say this because every forum thread eventually recommends it. Epsom salt is magnesium sulfate. Magnesium and calcium compete for uptake. Adding more magnesium when you have a calcium problem can actually make things worse. I tried it in year two because I read a thread that sounded confident. That was the worst rot year I’ve had. The most fruitless summer, you could say.

Save the Epsom salt for if you notice yellowing between the leaf veins, which is a magnesium deficiency. Different problem. Different fix. Don’t mix them up like I did.

Foliar Calcium Spray (the Fast Fix)

If you’re already seeing rot on a few fruits, you can buy a little time with a calcium spray directly on the leaves and developing fruit. A bottle of calcium foliar spray runs about $7 to $8 at the nursery. It won’t save the already-damaged fruits, those are gone, but it can slow down the spread to new ones while you fix your watering.

Some people make their own with powdered calcium dissolved in water. I’ve tried it. Results were uneven. The $7.89 bottle is probably worth it if you’re in rescue mode.

What I Actually Do Now

Transplant time: crushed Tums in the hole, handful of garden lime mixed into the bed soil, 2 inches of straw mulch over the top. Then I water on a schedule and try not to let the plants go bone dry between waterings, which in a Redmond July means paying actual attention every couple of days.

It’s not complicated. It’s just calcium and consistency. Two things I apparently needed to work on.

I like to think my tomatoes are finally getting the support they deserve. You could say they’ve really grown on me. (Sorry. I can’t help it. The tomatoes have suffered enough.)

Photo by Sandie Peters on Unsplash