Why is the Stem End of my Tomatoes Not Ripening?

Tomato with Yellow Shoulders
Tomato with Yellow Shoulders. Photo: Bruce Watt, University of Maine, Bugwood.org

When the Top of Your Tomato Remains Stubbornly Green

Anyone who has ever grown tomatoes know there are an endless cavalcade of problems waiting to afflict them. That makes it all the more frustrating when you manage to grow a healthy tomato plant full of luscious tomato fruits that simply don't seem to want to ripen. They feel soft. The smell heavenly. The show all the signs of being ripe, except the area near the stem refuses to change color.

What's up with that?

When the stem end of a tomato remains green or yellowish, it is aptly called "Green Shoulders". This is different from tomatoes that merely haven't finished ripening. With green shoulders, the green area is noticeably firmer or harder than the ripened part of the fruit. It's easy to spot on tomatoes that change from green to another color, like red or yellow, but it can also occur on tomatoes that remain green, like 'Aunt Ruby's'.

What Causes Green Shoulders on Tomatoes?

Normally the chlorophyll in an unripe tomato starts to break down at the blossom end and continues around and up the fruit. Green shoulders occurs when the chlorophyll either does not break down as the fruit ripens or if it breaks down too slowly. This can occur for a couple of reasons, both weather related. First, green shoulders can be caused by too much direct sun exposure. It may also manifest when temperatures remain high for a prolonged period of time.

Are Yellow Shoulders the Same Problem?

No. If the stem end of your tomatoes remains somewhat yellow, it means the fruit was unable to produce lycopene, the pigment that gives tomatoes their wonderful antioxidant properties as well as their red color. Lycopene production slows done when the temperature get warmer than about 75 degrees F.

So the cause is similar to green shoulders, but a different pigment is responsible.

What You Can Do to Prevent Green and Yellow Shoulders.

Once you notice green or yellow shoulders appearing on your ripened tomatoes, it's too late to correct it. Like blossom end rot and cracking, one the final symptom appears, there's nothing to be done.

However, you can take a couple of steps to try and prevent these shoulder problems before they occurs.

1. Make sure your tomato plants have plenty of foliage to shield the tomato fruits. Although tomato plants love heat and need plenty of sunshine to ripen their fruits, the sun doesn't have to shine directly on the fruits themselves. If you are having a particularly hot summer, the fruits will appreciate some cover. Go easy on pruning your tomato plants.

2. Choose tomato varieties that are less prone to the problem. Green shoulders seems to affect more heirloom varieties than hybrids. Not all heirlooms are prone to it, so don't give up on them entirely. You probably won't find tomatoes labeled as resistant to green or yellow shoulders, but you may find descriptions that tell you when a variety is prone to it.

3. If you're having a hot summer and all your tomatoes seem to be struggling with shoulder problems, you can try picking them when they are just starting to blush red and bring them out of the sun to finish ripening.

Unfortunately you may be compromising some of the vine ripened flavor by doing this, so it's only for extreme cases.

Can You Eat Tomatoes with Green or Yellow Shoulders?

Absolutely. The rest of the tomato should still be delicious. Just cut around the hard, unripened top and eat away. It takes more than a little inconvenience to render a home grown tomato inedible.

And don't forget, in some tomatoes, like 'Cherokee Purple', it's normal for the stem end to remain a little green even when they are fully ripe. You'll know it's green or yellow shoulders if the stem end is not just the wrong color, but also hard to the touch. And if you aren't paying attention and bite into one, you'll also notice it doesn't taste as sweet. So pay attention.