Why are my tomatoes rotting on the vine?

August 10, 2011 8:55 AM

Gardening question! I've got a potted tomato plant, with tons of green tomatoes. They were ripening up nicely, but when I went to pick some, they were rotting on the vine. Cracked at the stem and rotting in the center. The green ones are already cracking and darkening around the stem. See picture. What's wrong with them?
posted by Stagger Lee to science & nature (11 answers total)

There may be a disease. However, I had this kind of thing going on last year with some huge tomato variety. This year I switched a smaller one to try to alleviate it. Also, watering less. Tomatoes will apparently stuff as much water in there as they can, bursting the skin.

I've had no problems this year, but I've changed so many variables (above, plus mulching and location) I can't really tell what did it.
posted by DU at 9:12 AM on August 10, 2011

This sort of splitting happens when they get a lot of water after a long dry period. Once the skin is breached, the rot follows.
posted by jon1270 at 9:20 AM on August 10, 2011 [1 favorite]

Interesting. I'd increased watering because the leaves were wilting. You just can't win.
posted by Stagger Lee at 9:41 AM on August 10, 2011

They're still very edible, however. Just cut around the dry bits and eat the rest.
posted by Kurichina at 10:01 AM on August 10, 2011

That's why I mentioned my mulching. I don't know if it actually works this way, but here's what I'm thinking: the mulch keeps the soil moist. That means less watering. So the water level is more even and the plant won't take a BIG DRINK every 3 days (or whenever) and split the tomatoes. Instead, it takes little sips all the time.

But like I said, I'm also using a different variety in a different part of the yard.
posted by DU at 10:09 AM on August 10, 2011

have you tried watering in the evening, around sunset? this gives the plants the entire night to absorb the water as opposed to it evaporating in the sun. this can even out your wilting/overwatering cycle...
posted by sexyrobot at 10:10 AM on August 10, 2011

Yeah, definitely overwatering. Keep in mind when you're growing tomatoes that you're growing a crop of fruit, not a crop of leaves. Once the fruit is set, the leaves don't have to look great; their work is pretty much done, so worry less about how they look.

I don't know where you're located, but in many parts of the US, the time for the plant to flower more and set more fruit is past. (Generally, tomatoes won't set fruit if nighttime temps are above 75 or daytime temps are above the low 90s.) So, chances are that the fruit you've got is the fruit you're going to get for this season.

Also, if you're experiencing hot weather (and who isn't?) tomato leaves will wilt in the heat, but not necessarily from lack of water. They're just drama queens. Even if the plants look tragically wilted in the heat of the afternoon, wait till the next morning (when, presumably it will be cooler) to see if they perk up; if not, give more water.

(If you live in an area where fungal infections are a problem, watering at night is not a great idea, because it gives the pathogens extra time to get a foothold.)
posted by purpleclover at 10:24 AM on August 10, 2011 [2 favorites]

Ah purpleclover beat me to most of what I was gonna say.

Also, now is the time in most of the US to plant your fall tomatoes, if you're gonna do that. Once the seedlings or transplants are established you need to water as deeply (slowly) as possible as infrequently as possible. This is where the mulch comes in. It helps minimize evaporation directly from the soil. If you're watering your young plants every day, as is very tempting in this heat, their root systems won't grow deep enough, and that's when you get your vicious cycle of the leaves actually wilting away unless you water so much your fruit cracks.

The exact guideline varies depending on who you ask, but for me the surface of the dirt (under the mulch) might be bone dry, but if I can scratch down an inch or to and it's damp, they don't need water. I use soaker hoses in my garden and I'm able to water slowly for a couple of hours every two or three days even in this Texas heat.
posted by cmoj at 10:31 AM on August 10, 2011

Hey thanks everybody. The more you know!
posted by Stagger Lee at 10:34 AM on August 10, 2011

I was also going to chime in to say you can totally still eat those. I mean, not if they're actively rotted on the inside. A lot of times those cracks are pretty superficial.
posted by troublewithwolves at 12:47 PM on August 10, 2011

Longitudinal cracks are caused by inconsistency in growth patterns growth due to temperature changes and/or inconsistent watering. For example, if you have a few weeks of slow growth followed by fast growth, the tomato can crack. Tomatoes that have been overfertilized with nitrogen are more susceptible. Rain and overwatering can do it too; high temperatures plus water induce faster growth, causing fruit to crack.

It can happen with wide temperature fluctuations between the day and night as well. Anything that causes the tomato to alternately swell and shrink, in other words.
posted by oneirodynia at 1:34 PM on August 10, 2011