Green to Red but Not Green to Yellow? – Final Harvest Questions

Questions:

I still have so many green fruit ripening on my tomato plants. Should I pull up the entire plants by the root and hang them upside down in the garage to finish ripening? Before the first frost in my area, I went ahead and picked my yellow bell peppers while they were still green. Will they turn yellow if I keep them on a brightly lit windowsill?

- Gardeners in Albuquerque & Tucumcari

Answers:

The good thing about tomatoes is that they are classified as climacteric fruit, meaning they continue to ripen after being harvested, as long as they are mature. As I’ve explained in other articles, “Mature fruits are those with seeds that have fully developed and are viable. Ripeness refers to color, texture, and flavor, aka marketability.” Climacteric fruits, like bananas, avocados, apples, mangos, and tomatoes, are “often picked when they’re technically mature but not completely ripe so that fewer rot during transport.” Strawberries, raspberries, blackberries, citrus, pumpkins, and squash, among others, are non-climacteric fruits. These will not ripen after they’ve been harvested. “The difference has a lot to do with how much ethylene each fruit produces. Ethylene is a natural plant hormone (aka phytohormone or growth regulator) largely responsible for fruit ripening. The group of fruits that can ripen off the vine, so to speak, tend to be higher ethylene producers. Lucky for us, tomatoes are in this group.”

Yellow bell peppers picked before the first frost, when still green. Will they continue to ripen and turn yellow? Photo credit Argen Duncan

As Nebraska Extension Horticulturist John Porter puts it in his excellent blog post on this subject, “The only stage of maturity for non-climacteric fruits after harvest is….compost” found at Garden Professors.

This isn’t to say that all tomatoes are on easy street once they’re out of the garden. In a Plant Talk Colorado™ article titled “Ripening Tomatoes Indoors,” the authors explain, “One difficulty with ripening tomatoes indoors is controlling humidity. If the humidity is too low, fruit shrivels. If the humidity is too high, fruit molds. Some gardeners simply hang the whole plant upside down in a dark, cool garage or basement to let the fruit ripen gradually. In Colorado, fruits tend to shrivel from the low humidity” as seen in Plant Talk.

The method of upside-downing late-season tomato plants is recommended, or at least mentioned, in many blogs, articles, Facebook groups, and Cooperative Extension publications around the country. However, in this vast rabbit hole, I found just as many sources asking the question, “But why?”

Considering the bowlfuls of green tomatoes in my kitchen lazily reddening on their own, I am more comfortable in that second boat of skeptics. Why go through all that work? It seems like a hassle to dig them up, remove excess soil from the rootball, and drag them inside. Large tomato plants can easily weigh over 20 lb without even considering the weight of the fruit. Then there’s more work to hang huge tomato plants from the ceiling. One blogger even suggested hanging them in your attic. I don’t have an attic, but that sounds like a messy mess to me.

These red-but-wrinkly tomatoes are the very last of the 2,052 lbs. of green tomatoes harvested on Oct. 15, 2021 at the end of the study at the NMSU Agricultural Science Center at Los Lunas. These fruit turned red within 4 weeks of harvest, but I haven’t used them, so they’re showing their age—and perhaps indicating low humidity conditions in my kitchen. Photo credit Marisa Thompson

Hard work aside, what benefits could there be? One astute gardener pointed out that hanging plants might make sense for people who do not have counter space for stockpiles of ripening fruit. And I imagine that, in more humid climates, storing tomatoes while still hanging on the plant might mean slower decay rates compared to those clumped together in a box.

But are there actual benefits to the fruit? Not likely. By the time the plants are pulled from the ground, the tomatoes that have matured enough to ripen will continue to do so on their own, without all the fanfare. They don’t even need light. And studies have shown that once tomatoes reach a maturation phase called the “breaker stage” (or “breaker point”), the flavor does not improve by staying on the vine any longer. Yes, you read that right. I was surprised to learn all of this too. I’ll include resource links in the Desert Blooms blog.

In the end, if you try the upside-down method, set aside a pile to test in a bowl or box, take photos, document the experience, and share what you learn.

Okay, we’re ready to tackle question number two: Will the green bell peppers turn yellow if kept in a brightly lit windowsill? Well, we already learned that fruit do not need light to ripen. While the factoid about light is surprising, that’s not the most interesting part of the story.

Oh yes, the plot thickens.

Even though peppers (Capsicum spp.) are in the same family as tomatoes (Solanaceae, aka the nightshade family), peppers have been classified as non-climacteric. So don’t hold your breath waiting for those green bell peppers to become yellow. However, newer research performed around the globe and here in New Mexico has shown some pepper types to be climacteric and still others to be semi-climacteric. I was hopeful about the bell peppers. I finally ran out of steam and stopped searching when I read Porter’s thoughtful remark in the comment section of his blog post that strengthens the case for non-climacteric bell peppers: “(this is how you have both green and red/yellow/orange bell peppers available at the grocery store—if they continued to ripen [after harvest] it would be hard to have green bell peppers).”

Green tomatoes on plants that were brought inside before the first freeze in Tucumcari. Photo credits Susann Mikkelson

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!