Why are my tomatoes rotting on the vine?

One of the most annoying things to happen to a tomato grower is when it's so close to harvest and all of a sudden your tomatoes start to rot from the bottom. Ugh! Luckily that is a very definite condition called blossom end rot and it has a pretty simple cure.

Tomatoes with blossom end rot

Unfortunately you have no way of knowing if your plants are going to get blossom end rot until they start rotting, and it can take a little bit of time to fix. There are two steps to fixing end rot in tomatoes and if you use them both at the same time, things should turn around fairly quickly.

What does blossom end rot look like?

It starts out like a small brown bruise on the end of the tomato. If the fruit is fairly new, you can often see what's left of the flower hanging on. It always happens on the blossom end of the fruit...hence the name. 

This brown bruise will get larger and start to sink in. It will seem mushy at first, but will eventually dry out and harden, appearing leathery. Sometime mold sets in leaving a grey/blue/white patch on it.

What causes blossom end rot?

Blossom end rot is caused by a calcium deficiency. However, it's not always a calcium deficiency in the soil, but rather insufficient watering that is not allowing the calcium to be absorbed by the plant. 

So in order to fix the problem you have to both make sure there's plenty of calcium and plenty of water...but not too much, because over watering causes problems too!

If you put eggshells in your compost pile on a regular basis then it's probably not a lack of calcium in the soil. Lime is another garden additive that adds calcium and it's usually added to gardens in winter. If you don't use either, well unfortunately it's a little too late for them now.

Many people say that you can just crush egg shells and throw them on the ground next to the tomato plant and that will work to add calcium, but unfortunately it won't. The eggshells take a long while to break down enough to release the calcium, so even powdered egg shells won't take effect quick enough.

While you might be able to add lime to your soil now, I personally am not comfortable doing that unless you have a soil test kit. Lime increases the soils pH making the soil more alkaline. While tomatoes do enjoy this type of environment, if you already have a less acidic soil, adding lime can push it too far. Always test first.

Tomatoes with blossom end rot

How to fix tomato rot

Eggshells actually are the answer though! If you soak the egg shells in water for a few days, the calcium leaches out into the water which you can then use to water the tomato plants. 

Eggshells are full of calcium plus a little potassium, and we need to unlock those minerals from the shells. Crush clean eggshells and put them in a mason jar full of water. Allowed the mixture to set for a week or so then pour the water off and use to water your tomato plants.

After you've used all your homemade eggshell fertilizer, toss the shells in the compost and use new ones for the next batch.

The other factor in blossom end rot, is water. You're going to need to make sure the tomato plant gets a consistent amount of water, which can mean watering twice a week if it doesn't rain. The plant needs the water to pull the calcium from the soil anyway.

Consistent watering also keeps your tomatoes from developing cracks. Cracks form on developing tomatoes when they go through a period of drought, followed by heavy rain and then goes back through a period of drought, before getting a lot of water again. So, basic summer weather. Lol

Cracks can allow pests and disease into your tomatoes, so you really want to avoid these!

Cracks on fresh tomatoes

When you water the tomatoes you want to make sure you water them deeply. Water directly at the stem/roots. Water enough so that the soil gets completely wet about 6 inches down into the ground. That should be enough for a few days and you can get away with only watering twice a week. 

Adding a deep mulch can keep the ground around the tomato plant from drying out too much between watering. The better you can keep the moisture in, the better the plants will be able to absorb the moisture and the calcium they so desperately need.

Related reading: How to grow tomatoes in containers.

Unfortunately the affected tomatoes need removed from the vines and composted. I sometimes cut away the rotted part and feed the good parts to the chickens and they seem to like them. You have to remove them from the plants though or they will attract pests and other diseases.

So: remove the bad fruit, give the plant a drink of water, make eggshell water then water the plant with it and you should have perfect tomatoes growing again shortly!

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  1. Thank you, I am delighted by your good advice. How about adding a tablespoon of bone powder to the pot? I do it and it gives me good results.

    1. That's a smart idea! Bone would be high in calcium which is what the tomatoes need. Good thinking!