How to Make Tomatoes Turn Red When They Refuse to Ripen on the Vine

How to Make Tomatoes Turn Red When They Refuse to Ripen on the Vine

Seeing red? If you’re looking at your homegrown tomatoes, I hope they are a bright, cheery red color as they’re ripening on the vine.

And yet, I know that even experienced gardeners have times when their plants are nearing that all-important harvest date and the fruit is still hard and green.

A vertical close up picture of ripe red cherry tomatoes still on the vine, pictured in bright sunshine on a soft focus background. To the center and bottom of the frame is green and white text.selecting your dream heirloom varieties and planting your crop.

A close up of a large ripe tomato on the vine, pictured in light sunshine on a soft focus background.Why Are Ripe Tomatoes Commonly Red?

If your plants are producing fruit that isn’t a vivid crimson, it’s comforting to know that lots of gardeners have that complaint. After all, we all want red tomatoes!

But did you ever stop to ask why these fresh tomatoes us home growers find so desirable are red?

There’s a scientific explanation, and knowing about it can help you with your own fruits that stay stubbornly green when you want them to be a nice red color.

A vertical picture of a vine laden with an abundant harvest of bright red 'Roma' tomatoes, with soil in soft focus in the background.4 Reasons Your Tomatoes Won’t Ripen on the Vine

As I know from experience on more than one occasion when my vines were stubbornly holding on to hard, green fruit, you can’t take this phenomenon personally.

A close up of a tomato vine with green fruits slowly ripening in the bright sunshine, pictured on a soft focus background.1. Temperatures Are Too Warm

If your tomatoes seem permanently paused on green and it’s still warm, heat could be the cause.

It’s hard to believe this about such easy-to-grow garden vegetables, but they can be a bit temperature sensitive. Along with ethylene, temperature dictates when the pigment will begin to change.

A close up of dark red fruits growing on the vine, covered in droplets of water on a soft focus background.2. Temperatures Are Too Cool

On the flip side, cooler weather can also put a stop to those desired changes that will turn your crops a rosy shade. Again, you’re seeking that optimal 68-77°F range for them to ripen to a sporty red hue.

A close up of a plant in the frost with unripe fruits pictured on a soft focus background.based on your seed packets or plant tags.

What to do if the weather should get cooler still?

If your area sustains nighttime temps lower than 50°F paired with daytime temps under 60°F, and this lasts for two weeks or more, the transformation to that lovely red shade that you’re going for will halt completely.

Nor will your plants set fruit to ripen when the air is colder than 50°F. You might get some green fruits if your plants are trying to set fruit in 50-55°F weather, but count on them to also develop odd shapes and soft spots.

A vertical close up picture of green tomatoes growing on the vine, surrounded by foliage on a soft focus background.Protect the plants with row cover, an old bed sheet, or even a plastic tarp.

Once a tomato plant is hit with freezing temperatures, you can banish any hope for the green fruits to come to harvest, and for the plants themselves. Unfortunately, you won’t be able to salvage any fruit at that point.

A close up of large vines growing in a greenhouse with green and red fruits in the process of ripening, fading to soft focus in the background.3. Wrong Variety for Your Growing Season

If you’re growing what you hoped would be juicy red tomatoes but they’re still green, and frost is approaching, you may have chosen an inappropriate variety for your area.

A close up of a dead plant with wilted leaves and green fruits pictured in the garden on a soft focus background.where there’s a short growing season, it’s important to select short-season cultivars so the green fruit has time to grow to its full size and turn red before temperatures drop below 50°F.

A few of the best short-season varieties include ‘Early Girl,’ which produces ripe, red fruit about 50 days after transplant, and ‘Juliet,’ a red grape cultivar that’s ready to harvest about 60 days from transplant.

A close up of a vine with unripe green fruits in the foreground and ripe fruit in the background, pictured in bright sunshine, with foliage in soft focus in the background.4. Stressed or Overgrown Vines

Like every living thing, tomato plants only have so much energy. If they’re using too much to grow leaves and flowers, they may not have any energy left to turn green fruit red.

A close up of gloved hands from the right of the frame holding pruning shears and clipping green, unripe tomatoes from the vine in light sunshine, fading to soft focus in the background.When You Should Compost Green Tomatoes

This is one of the many reasons why I love growing my own fruits and vegetables. So much good can come from this, even from produce that doesn’t make it to harvest.

Green tomatoes are a great example. If you’ve chosen a variety that won’t ripen on the vine in time, or an unexpected bout of chilly weather strikes late in the growing season, you can still get some value from the green fruit by adding them to your compost pile.

A close up of a dead tomato plant with a few green fruits still on the vine, prior to placing it on the compost pile.our handy guide on composting to learn more about all the things you can add at the end of the vegetable growing season.

How to Ripen Green Tomatoes Indoors

I’m not gonna lie. When you have to resort to trying to make your unripe harvest turn red indoors, you’re not going to get the same great taste as you would with vine-ripened homegrown fruit.

For one thing, while you can make them ripen a bit indoors, you can’t make it produce the sugars that make homegrown tomatoes taste so great. You can encourage your green harvest to produce more ethylene, but that doesn’t produce sugar.

A close up of a white plate with red and green tomatoes set on a blue painted windowsill that is rotting slightly and peeling.

And whatever you do, resist the temptation to stash your ripening tomatoes in the fridge. They need to turn red at room temperature, or they’ll lose every bit of their tomatoey flavor.

Love Is Like a Red, Red Tomato

When you make all that effort to grow your own luscious tomatoes, it’s only fair that they be a delicious, eye-appealing red at harvest time.

If you didn’t have time for even a last-minute effort to make your crop turn red on the vine, remember, there’s always next year.

A close up of a bunch of ripe cherry tomatoes on the vine, ready for harvest on a soft focus background.growing tomatoes in your garden, you’ll find even more helpful info here:

Rose Kennedy

An avid raised bed vegetable gardener and former “Dirt to Fork” columnist for an alt-weekly newspaper in Knoxville, Tennessee, Rose Kennedy is dedicated to sharing tips that increase yields and minimize work. But she’s also open to garden magic, like the red-veined sorrel that took up residence in several square yards of what used to be her back lawn. She champions all pollinators, even carpenter bees. Her other enthusiasms include newbie gardeners, open-pollinated sunflowers, 15-foot-tall Italian climbing tomatoes, and the arbor her husband repurposed from a bread vendor’s display arch. More importantly, Rose loves a garden’s ability to make a well-kept manicure virtually impossible and revive the spirits, especially in tough times.

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