Two of our most widely-cultivated summer vegetables are closely related.
The tomato and potato belong to the solanaceae family. And when you have grown the former for a number of years it is difficult to avoid ascribing certain human traits to it.
For me, tomatoes are the best plants at communicating their needs to the grower.
They respond quickly to a range of environmental stimuli, and even the casual observer can work out what they want. Miss a watering session on a particularly hot day and the whole plant begins to droop. Soak the compost then retreat for a couple of hours, and when you return the plant will be standing like a guardsman on parade, seemingly fully recovered.
However, the payback for failing to water on time often arrives a week or two later when you notice blossom end rot on some fruits. Several factors may contribute to this physiological problem but the catalyst is almost certainly a brief shortage of water in cells at the very tip of fruits. This causes them to collapse and engender a domino effect.
It could be argued that several other plants droop when signalling a lack or excess of water, fuchsia and French marigold in particular, but the tomato ‘talks’ to us about much more than this. When the leaves are curled like a clenched fist it’s not because the plant is angry, stressed would be a better explanation, because intense sunlight has sent the food-making process into overdrive and there’s a limit to the amount of storage space for starches.
Leaf curling reduces the surface area thus limiting photosynthetic activity. But the gardener can avoid this by offering semi-shade to tomatoes grown under glass. Install adjustable blinds or fine netting for permanence or paint the glass with proprietary shading liquid that can be removed in autumn to restore full light. In days of yore a cheap and cheerful solution came from mixing whitewash powder with water and adding sour milk to cement the relationship. This was applied to the outside glass and did the job, but was the very devil to remove.
Several plants are ‘one act wonders’ when it comes to communicating their problems. The typical inter-veinal yellowing of leaves shown by some, roses in particular, suggests a magnesium deficiency, so we reach for the
magnesium sulphate (Epsom salts) and by applying small amounts at 10-day intervals, hope to solve the problem.
But tomato plants take this leaf language to another level. Leave them standing in an unheated poly-tunnel or cold greenhouse, too early in the season without fleece protection, and expect to find blue-tinged leaves the morning following frost. You can almost hear them complaining. They do recover but the experience interrupts their growth pattern.
No matter how good the compost they are planted into, tomatoes are gross feeders and demand more food than it can offer as the fruits swell. This is why we treat them on a weekly basis, even alternating the type offered to cover all eventualities. I work between Phostrogen and Maxicrop.