Expert garden advice from the RHS: my tomato plants are tall and spindly, do you have any suggestions?

The experts at the RHS answer your gardening questions...
Question: Although I am growing my tomato plants in a small greenhouse which gets a lot of heat and light in summer, they are very tall and spindly, and the stems have a lot of distance between them. There are some flowers but not as many as I'd hoped. They are obviously not happy, but why not? I should probably add that I am new to growing them so would be grateful for any advice.

Answer: It may be that your tomatoes were growing too closely together when they were younger or in too warm conditions earlier on. Although tomatoes love warmth and grow well in greenhouses, they can start to suffer once the temperature gets up to 30 degrees Celsius and above: leaf scorch, flower drop and distorted leaves can occur. The key is to have shading and good ventilation. The greenhouse door can be open all the time. There should be a set of louvres in the glasshouse wall, which don't come as standard, but can be retrofitted, and the vents in the roof should be open. You could keep a maximum/minimum thermometer and consider fixing shading material to the inside of the greenhouse so the temperature can be maintained at around 25 degrees Celsius

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