The Simple Fall Trick that Ripens the Last Green Tomatoes, Fast

If you're wondering how to ripen green tomatoes on the vine for maximum flavor, this quick trick will force tomato plants to put all their energy into producing red fruit, fast. It’s been a fantastic year for growing tomatoes and finishing the season will be all the better if you’re picking juicy ripe tomatoes rather than green hard-as-a-bullet fruit that fill your windowsills for weeks.

Tomato plants are driven by an incredibly strong survival instinct, and this simple gardening hack flips this force of nature into panic mode, hoodwinking plants to crack on with ripening fruit that’s already formed. You’ll enjoy far more flavorful late-season tomatoes, and have a free windowsill to boot!

Part of the Weekend Win series, persuading a tomato plant to ripen its last fruits fast is one of those easy jobs that brings a big reward, and guess what? All you need is a pair of hand pruners.

How to Trick Tomato Plants into Ripening the Last Fruits

1. Understand How a Tomato Plant’s Survival Instinct Works

Tomato plants have stronger survival instincts than humans – and that’s a fact. With around 25% more genes than we do, many of a tomato plant's genes come in pairs: one to look after the necessary day-to-day basics of life, and one that only comes into play when the plant is stressed. That means tomato plants adapt incredibly quickly to growing conditions, and we gardeners can use that to our advantage to ripen those precious last fruits.

In late September, days are still warm enough that a tomato plant thinks there’s time to grow more fruit, and so produce more seeds for survival. However, nights are cold enough to halt the ripening process on its already-formed green tomatoes. So while the tomatoes are still ripening, it's a very slow process. This simple task, however, will trick the plant into panic mode so it puts all its energy into ripening tomatoes, pronto.

2. Halt All New Growth

Before you perform the magic trick to focus tomato plants on ripening fruit, you need to prevent it wasting energy on new growth. You may well have done this already as it’s a regular part of September tomato care, but if not, use hand pruners such as these Fiskars Bypass Pruners from Lowe’s to snip off the main growing tip at the top of the vine. Cut off any yellow flowers and newly-formed tiny green tomatoes, too, and keep checking leaf joints and removing any fresh sucker shoots.

3. Strip Away Lower Leaves

Now you’ve got your tomato plant’s attention, you need to strip off all the leaves on the bottom third of the plant. Cut stems flush with the vine so the base is completely bare apart from any lingering fruit trusses. This stresses the plant, which now thinks winter has arrived early, so it puts all its efforts into ripening fruit to ensure the seeds it's already produced survive.

Pruning tomato plants in this way looks harsh but it's common practice in commercial tomato-growing operations, so don't worry a jot! The plants now only need enough energy to finish ripening already-formed fruit rather than fuelling new growth, so they'll be just fine.

4. Cut Watering

The next step to trigger your tomato plants to move into full emergency mode is to cut the water supply to stress them a little more. The plant will think it's about to die and, when a plant goes into this survival-at-all-costs state, it physically releases a heap of ethylene gas, the ripening hormone, as a last-ditch measure. This surge sends a strong signal to green fruit to rush seeds to maturity, so tomatoes ripen far more quickly.

To ripen tomatoes growing in the ground, you should stop irrigating completely, as plants will still be able to source some moisture from the ground. In containers, grow bags or a greenhouse, drastically reduce watering to the bare minimum to trigger this survival mode and accelerate the ripening process. A light watering once a week if it doesn't rain at all, or if you see the main stem starting to droop, is all a plant needs to stay alive at this late point in its life.

5. Keep Plants Warm

It’s not sunshine hitting the skin that ripens toms, but the warmth of its rays. We all know what it’s like to bask in the warmth of late-season sunshine so, in all zones, cut off any foliage that’s directly shading fruit trusses higher up the vine. This lets sunlight – and levels are getting lower all the time as fall approaches – hit the fruit directly for maximum warmth.

The ripening process shuts down as soon as air temperatures drop below 50°F (10°C) so, depending on your zone, you may need to take additional steps to keep tomato plants warm. Having a garden thermometer – whether it’s a handsome analog thermometer like this from Amazon or a weatherproof digital thermometer such as this, also from Amazon, takes out the guesswork and helps you make good decisions.

If you want to ripen tomatoes in a greenhouse, then the simple task of closing the door and vents in late afternoon, then opening them in the morning, traps warm air inside.

Having some horticultural fleece ready to throw over plants when a cold night is forecast is a smart move if you’re growing tomatoes outdoors. A breathable plant cover like this from Walmart is cheap, light enough not to damage plants and is easily pegged to tomato supports, and will help to keep the ripening process on track.

Try this simple fall trick and you'll have rapidly ripening tomatoes, and I'll wager you’ll be surprised how fast it works, and how strong a tomato plant's survival instinct is. And that's just as well as, depending on your USDA zone, you may not have much ripening time left. Tomato plants have zero frost tolerance and, with such a high water content, fruit that freezes is immediately ruined. Keep an eye out for your impending first frost so you can cut unripe fruit beforehand and ripen any remaining tomatoes indoors – but you won't have many, if any, green tomatoes left if you tried this simple fall trick.

Do remember to save tomato seeds for free plants next year before the end of the season, too, selecting good-sized toms from your strongest plants.

If you do have a few left to ripen, it’s good to know that popping green tomatoes in a brown paper bag with a banana or simply putting them inside a closed kitchen cupboard is a far better method than a sunny windowsill, and cuts ripening time down to a week.

More Weekend Wins

This feature is part of the Weekend Wins series, packed with quick and easy 10-minute tasks and gardening tips and tricks that bring a big reward.