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How to Ripen Tomatoes Successfully

September 03, 2010
Tomato Harvest in Seattle

Tomato Harvest in Seattle

Seattle gardeners (as well as others elsewhere) struggle to get tomatoes to ripen. Cultivating the plants to grow green and lush and even to fill them with green fruit isn’t always difficult. But getting the fruit to ripen before the growing season wanes can take some wily moves by gardeners.

The first trick is to plant tomatoes designed to ripen in short, cool growing seasons. A few tried and true slicing varieties include Oregon Springs, Peron, and Siberia. Most cherry and small-fruited tomatoes like Stupice will easily ripen as well. And, for sauce tomatoes, heavy-setting Saucy Paste continues to perform beautifully.

Still, a little manipulation late in the season can help ensure those heavily-set fruit actually show colors other than green.

Begin by clipping out flowers. At this point in the growing season (late August and later), it is highly unlikely that any new flowers will have time to get pollinated and make it all the way to ripe fruit. By clipping them out toward the end of the season, the plant will be encouraged to throw it’s energy into current fruit-set, causing the fruit to ripen.

Hellstrip Saucy Paste Ripening after Late Season Flowers are Clipped

Hellstrip Saucy Paste Ripening after Late Season Flowers are Clipped

If you haven’t already, stop fertilizing, particularly nitrogen fertilization. Nitrogen is used, mainly, for green growth in plants. Withholding it will keep the plants from producing much more green growth. Too, withholding all additional feeding will further stress the plants. As the parent plant becomes stressed, it will divert energy toward its fruit, which is where its genetic code resides in seed for years to come.

And, if you can, hold back on water. Some may fall from the sky, and you can’t do much to control that unless you’re set up with hoop or tunnel houses (more on that follows.) But, by holding back on water, you can again stress plants. As your annual tomato plants begin to die back for the season, they will throw their reserves into the fruit. Note that withholding water requires a delicate balance. Withhold too much, and your plants may just die with the green fruit on the vine. Withhold too much too soon and then flood the plants, and any fruit that has begun to ripen may crack from the sudden in-rush of water to their juicy fruit with delicate skin that no longer has the capacity to expand as water is added.

If your tomatoes are grown in containers and rain is coming, try moving the containers to a protected space to protect delicate skins from cracking. Greenhouses, plastic tunnel houses, tall cold frames can help protect potted tomato plantings from abundant fall rains. Plus, the plastic coverings can help retain heat. Just be sure to maintain airflow so you don’t encourage late blight and other fungal diseases.

Yesterday, in my own garden, I clipped all the flowers off of my in-ground plants, took out late suckering shoots, and reinstalled plastic tunnel houses over the plants. The tunnels are open on each end so air can flow through them. Rain can fall on them and sheet down to the soil to saturate plant roots without splashing the leaves and fruit (too much). This morning, I awoke to cool temps and rain, so we got those hoops in place none too soon!

So, as you’re out in the garden this labor day weekend, trolling through your plants for hints of orange, yellow and red, if you do nothing else, be sure to snip out those flowers at the top of the plants. Odds are you’ll see more color within just a few days.

2 Comments

  1. Erica says:

    Great tips, thank you! Here’s to ripe tomatoes!

  2. [...] Briefly explained: suckers are the new shoots that emerge out of a tiny bud the base of a leaf, where the leaf base connects to the stem. It’s important to be sure that the shoot isn’t a flower shoot as these are what produces fruit. And, its important not to remove the main, tip shoot on the plant if you want it to keep growing upward. (Sometimes tipping out the whole plant & removing remaining flowers is a good idea; but this comes a little later in the season as discussed here.) [...]

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