QuestionsHow to growFlowersSummer colour from seedSweet pea too tall 0 Vote Up Vote Down Dale Harrow asked 14 years ago My Sweet Pea have grown over 7ft tall and are difficult to manage, is it possible to cut them by 1/3 and will this encourage new growth 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 7 years ago Once the top of mature plants is removed, they are very unlikely to branch lower down. Train the tops of the plants along the top of the support.Â