Why are my tomatoes still green?

Jan 10, 2021 | Gardening tips, Nightshades, Tomatoes | 2 comments

There’s been a fair bit of consternation this tomato season about when, or if, tomatoes are going to ripen. The good news is that they probably will but there are some things to take into account and some not to do.

Like all vegetables, the movement from seed or seedling to fruit is complex, and involves many simultaneous processes. When plants are faced with weather extremes, some of these processes can be thrown out of balance. There’s an order that needs to happen: seed germinates, seedlings begin producing foliage, (generally quite a lot of it), roots expand, flowers form, fruit forms, plant produces chemicals for colour, texture and flavour, and fruit ripens.

In ‘normal’ conditions this process is flawless, and the tomato plant allots enough energy to each requirement to produce full size fruit in 25 days and the first ripe fruit in about 50 days. However, we no longer have such conditions. The plants deal with constant changes in air temperature, often suffering significant rises and falls in short periods. They also have to deal with the same beneath the surface where constant changes in soil temperature disrupt the normal growth pattern.

Whether your tomatoes are ripening now may be a matter of luck – the luck of when you chose to plant them. It seems that tomatoes planted in October are ripening more readily than those planted in November and later, even though there has been enough time for all to ripen in normal conditions. This may reflect less extreme weather earlier in the season. You may notice tough skins if you are getting ripe tomatoes now and this is caused by high temperatures and inadequate water.

Rather than try to force your tomatoes to ripen, be patient and believe in the wisdom of the plant. Don’t add fertiliser as this will cause the plant to put energy into growing foliage and roots rather than producing compounds for colour, texture and flavour. Mulch the roots and water regularly to attempt to keep the soil temperature below 26.5 degrees celsius. Shade on only the hottest days, and then remove the shade once the temperature drops, so as to not further slow the ripening process.

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Written by Robin Gale-Baker
First published in the Local Food Connect Newsletter