Q.I have a tomato or what looks like a tomato growing on a cucumber plant. Have you ever heard or seen something like this before?
(Mr John Cox, 16 September 2008)
A.The likelihood of an actual tomato growing from a cucumber plant is nigh on impossible. This is largely because the two plants are a completely different genus – Tomatoes are part of the Nightshade (potato) family, whereas Cucumbers are members of the Cucurbit family, along with pumpkins, squashes and courgettes. There have been a couple of instances where people have claimed to be able to grow tomatoes from cucumber plants, where the seeds have been germinated inside the fruits or grafted ‐ but these have been largely dismissed as hoaxes.
The only vegetable or fruit that comes close to a cross between the two is the unrelated ‘Snake Tomato’ Trichosanthes cucumerina – a vine‐growing gourd that is said to resemble a cucumber but taste distinctly tomato‐like. However, this is probably not related to this case at all.
One scenario is that the cucumber plant is a different variety of cucumber – some cucumber varieties have been engineered to produce thicker, shorter fruits, such as the African Horned Cucumber, Crystal Lemon Cucumber, Silor Cucumber and Rocky F1 Cucumber. These can differ in width, length, taste and skin colour to the more generic and common long, green varieties of cucumber.
Another reason for the tomato‐like fruits appearing is that the cucumber plant is suffering a deficiency that is causing the fruit to appear shorter and chubbier, resembling an unripe tomato rather than a cucumber.
Potassium deficiencies in cucumbers can cause the fruits to appear short, thick and distinctly dumbbell shaped. One way to spot potassium deficiency in cucumber plants is when the leaves start to show signs of chlorosis (pale leaves that are unable to photosynthesise), followed by necrosis (withering and dying) of the leaves.
There is another instance when cucumbers can be stunted and appear tomato‐like. And whilst the mature fruit that has already formed can’t be changed, you can tackle the problem before other fruits have had time to start growing. Firstly, when the temperatures between night and day are very close together, this can cause stunted growth in the cucumber fruit. Ideally you need around 10 degrees Celsius between night and day temperatures to encourage a more ‘normal’ lengthy fruit. The humidity of the environment that the cucumber plant is growing in can also affect the growth of the fruit. You want the cucumber plant to work very early in the morning, and decreasing the relative humidity will help in this respect.