A: So are mine. There are many possible causes, including plants grown from inferior seed. However, I am reasonably certain that this year the small size is caused by weather. Some of my Early Girl plants came from new seed, some from last year’s leftovers. All the plants are growing small tomatoes, but the leftover seed is from a supply that produced bigger tomatoes last year. Do I know which weather problem might be responsible? I have no idea, and there are several choices this year.
Source : http://ravallirepublic.com/lifestyles/home-and-garden/article_e587f360-0f86-11e3-8550-001a4bcf887a.html