Green Tomatoes in September: Ripen Them Instead of Binning Them
The nights are turning cold, nothing more is happening on the plant – and yet the trusses are still full. Here's how to turn those green tomatoes into a real harvest.
From mid-September on, night temperatures drop far enough that tomatoes barely gain any colour on the plant. Below roughly 12 °C the fruit essentially stops producing its red pigment – it stays green no matter how long you wait. That’s no reason to clear the bed in frustration: most of those fruits will ripen indoors without any trouble.
Which green tomatoes will still ripen
Not every green tomato turns red. What matters is whether the fruit has already reached its full size. Look at the blossom end – the side opposite the stem: if it’s paler, creamy-green or slightly yellowish rather than deep green, the fruit is far enough along to ripen off the plant. The skin will also have a faint sheen and give a little under gentle pressure.
Small, rock-hard fruits that are uniformly dark green are a different story. They haven’t developed far enough and will only shrivel indoors. Those can go on the compost with a clear conscience.
How to ripen them fastest
Tomatoes need warmth to ripen, but not light. They do best at 18 to 20 degrees, spread out in a shallow crate or on newspaper somewhere dim – a kitchen shelf, pantry or utility room. One thing to avoid: the fridge. Below about 12 degrees the fruit takes chilling damage and loses its aroma – and that doesn’t come back, even if it does turn red later on.
Adding a ripe apple speeds things up noticeably. Apples release ethylene, and that gas is exactly what triggers ripening in tomatoes. Depending on how far along they are, it takes one to three weeks. Check every few days and take out the ones that are done, so air can keep moving between the fruits.
Cut the whole truss
If several fruits are hanging on one truss, cut it off whole – with a bit of stem attached. Hung upside down somewhere frost-free and airy, the fruits ripen more evenly than they would loose in a crate, because the truss still holds a little moisture.
This is especially worth it when you’re clearing the bed ahead of the first frost anyway. Tomatoes aren’t frost-hardy – a single frosty night is enough to turn the fruits glassy and mushy. So keep an eye on the forecast and clear a few days too early rather than one day too late.
Sort them before you store them
Before the fruits go into the crate, go through them one by one. Anything with brown, leathery or sunken patches comes out – that’s usually late blight, and infected fruits rot through quickly in a warm crate. A single one you miss can ruin the whole batch.
Infected foliage and rotten fruits don’t belong on a cold compost heap, because the spores can survive there. The green-waste collection or general waste is the safer route. Healthy stems and leaves can go on the compost as usual.
Eating them green? Only with care
Unripe green tomatoes contain tomatine, a bitter-tasting glycoalkaloid related to the solanine in potatoes. As the fruit ripens it breaks most of it down, which is why fully ripe red tomatoes are perfectly fine. Raw, still completely green fruits are another matter – don’t eat them in quantity, and it’s better to keep them away from children altogether.
Cooking doesn’t solve it either: tomatine is heat-stable and survives preserving. That’s why traditional green tomato chutney is eaten in small amounts and usually made from fruits that have already started to turn. If you’d rather not think about it, just let the tomatoes ripen first – then the question never comes up.
One thing to note for next year
How many green tomatoes you’re left with depends a lot on planting date and variety. Small-fruited cocktail and bush tomatoes usually finish well ahead of large beefsteak types – so if you had to harvest a lot of green fruit this year, that’s a useful hint for choosing varieties in spring.
In Rootivo, each variety’s profile shows its harvest window, and the garden journal lets you record when the season actually ended for you. Come next September, you’ll know exactly when it’s time to bring the trusses in.
Im Lexikon: Tomate