Sadly, my anorak-level fixation with the fruit makes much of summer a long and frustrating wait for them to ripen. Without a greenhouse, my outdoor tomatoes often only just have time to ripen before being clobbered by autumn, not to mention the ever-present threat of late blight. If this sounds familiar to you, fortunately there are several evidence-based techniques anyone can use to speed the ripening of your little flavour bombs, even at this time of the year.
Aside from the coddled conditions of a greenhouse, which cheat the seasons forward, the single most effective way to get earlier crops is to pick a variety whose genetics trigger it into fruiting early. There are many, but the very earliest is a surprising one: Sungold. This beautiful orange cherry tomato famed for its sweetness consistently ripens weeks before any other for me — yet no-one else seems to mention this. Definitely my choice for the impatient.
Even this late there are two things you can do to force your plants into directing their energies into ripening fruit. First, there is pruning. Limiting the growth of new leaves and roots gives the plant less drains on resources that could go into fruit maturation. This is as simple as keeping on top of removing all side shoots, as well as snipping out the top growth after the plant has produced four trusses.
Want them even faster? Research shows that the fewer trusses you let the plant produce, the quicker they ripen, with an interesting side effect that is each fruit is larger and measurably sweeter, and even more nutrient-dense. I often leave just one truss on some of mine for the best-tasting, earliest-ever fruit. Root pruning is simple, too. Insert a spade into the ground 40cm from the stem of a plant and work your way round in a circle to slice through the longest roots.
Salt-water treatment has been consistently shown to speed tomato ripening in scientific trials. This involves diluting 60g of sea salt into three litres of water and drenching the mixture over the soil once or twice as the tomatoes are ripening, being careful not to wet the leaves. This reduces the plant’s ability to uptake water, mimicking a drought.
The plants react to the stress by speeding up their ripening, but also producing more sugars and aroma compounds that can improve flavour. As the plants are mildly dehydrated, too, this concentrates the fruit even further, with delicious results. At this concentration and application rate, there is no risk of salt accumulating in your soil — in a few weeks it will be washed away by rain. Good luck!
— Guardian News and Media
