Anne Swithinbank’s Masterclass
QMy greenhouse tomatoes in growing bags are starting to look miserable. Apart from feeding, which I have been doing, is there anything I can do to keep them going a bit longer?
Ada Montgomery, Epsom, Surrey
AAs with many crops, end-of-season tomato plants can look sorry for themselves, especially in a greenhouse. Trained to 6ft (1.8m) or more as cordons (by having their side shoots removed), plants often exhaust themselves by setting many fruit trusses and are stressed by high temperatures. Roots soon run out of space in growing bags, and even those planted in borders can be affected by dry soil at lower levels.
By summer’s end leaves might be curling, with yellowing between the veins, but plants can still support ripening fruit, and trusses will keep on developing into September. Look at the plants to find out what will help them ripen and deliver a good batch of late fruit. Perhaps there are also lessons to learn for next year.
Potting tomatoes on until they reach a 9in (23cm) pot is a slightly roomier alternative than three to a growing bag, helping them stay healthier for longer. Should greenhouse temperatures rise rapidly to 100ºF (37ºC) on sunny days, consider applying a sparse layer of shading to the south and west-facing roof and sides. Shading mix can be applied through a sprayer, or pin up thin net curtains or fleece that can come down again during long gloomy spells.
You could also try successional plantings. I often sow as early as January or February, placing pots in a heated propagating case or on a windowsill over a radiator. Plants are taken to the greenhouse for light, but ferried back indoors on cold nights. These early starts are generally of large-fruited tomatoes.
More sowings in March of ‘Black Krim’ or ‘Gardener’s Delight’ come next, then a May or June sowing of sweet cherry ‘Sungold’. By sowing in this way, you have fresh plants delivering fruit throughout the growing season.