Jessica Davidson, of Balclutha Primary School, asks :-

How did this happen to my tomato?

Mike Malone, a Plant and Food Research summerfruit breeder who once was a tomato breeder, responded.

The picture shows a fruit that looks like two tomatoes growing together. Other shapes are also possible such as beaks and bulges. Generally, misshapen tomatoes are caused by factors that affect pollination and the growth of the floral parts.

Cold nights and low light conditions particularly during winter are usually the main cause. Under these conditions, the anther sacs which contain the pollen fail to release pollen resulting in incomplete pollination.

Flowers that are not fully pollinated can give fruit with strange shapes with some fruits looking as if they were fused together. Tomato growers who raise winter tomato crops have to heat their greenhouses and grow the tomatoes through the poorer light conditions. To encourage good pollination under cool growing conditions and low light, growers put bumble bee boxes into their greenhouse crops. The home gardener might not have access to bumble bees but can mechanically stimulate pollen release by using some sort of vibrating instrument to help burst the anthers and release pollen on to the stigma. An old battery powered toothbrush works well for home gardeners.

During summer, it is usually not necessary to do anything when temperatures are high and light is good as the modern tomato is usually fully self-fertile under these conditions.