Increasing tomato yields with less plants
Tomatoes are the most cultivated greenhouse vegetable (fruit) in Britain, and rightly so because nothing beats the flavour of home grown fruits.
They are easy to cultivate but can quickly get out of hand. During summer they grow rapidly when temperatures rise above 15 ˚C. If they experience cold then, like us, they turn a bluish hue but quickly recover. This is not surprising as they originate from the warmer climes of Central and South America.
In nature they grow naturally as vines supported by other vegetation and scrambling along the ground rooting as they travel. This ungainly habit can be tricky to manage in a greenhouse and needs taming. Success is found by avoiding a ‘thicket’ of stems, which seldom produce large numbers of quality fruit and provides perfect conditions for mildew to develop as soon as the weather cools during autumn.
The usual scenario is that plants grow fast as the weather warms, then within a short period they reach the eves of the greenhouse. Then faced with a dilemma: do you train them up the greenhouse roof; keep removing the tops to prevent them getting any taller; or let them flop around and do their own thing?
Last year, I decided to adopt a different approach, that varies slightly dependent on whether you are growing cherry tomatoes or the larger fruited type. For the larger fruited cultivars I turn plants into a double cordon, a training method borrowed from growing apple trees in a small space. A double cordon allows two trucks to an apple tree, normally trained against a wall.
Back to tomatoes, when plants reach 15cm in height remove the growing tip (this is easily rooted if more plants are needed). This encourages side shoots. Select two of the strongest removing the remainder. Transfer your plant to its final location and treat each of the plant’s two stems as if they are two separate plants. Tie each stem to its own cane or string separated by around 25cm. Continue to remove all developing side allowing just the two stems to grow. This produces a double stemmed plant with a shared root system. Dividing the plant’s resources in this way produces a shorter, much more manageable and productive specimens.
Cherry tomatoes can be much more vigorous than the larger fruited types. In the books we are encouraged to leave the side shoots to create a bushy plant. Adopting the traditional method I find plants are productive early in the season but as their growth rate increases flowers become lost in foliage and stems resulting in a poor fruit-set and fruits you can't see to pick because they are hidden.
My method is to develop a plant with just four stems, removing side shoots along their length. This allows a more manageable plant, provides air circulation around the flowers increasing pollination and cropping.
This year I've just grown two cherry tomato plants and we have had so many over the past few months we've almost overdosed. Also, in late September they are still highly productive and still producing more flowers. I have had to train in the eves of the greenhouse, but this also means there is plenty of air circulation around them, especially when I open the vents.
