Ask Experts & Get Answers to Your Questions - ASAP
Welcome to Just Answer and thanks for your question. It's difficult to imagine Spring anywhere in England (including London) without bluebells, daffodils, hyacinths, crocus, rhodedendron, tulips, pansies, sweet peas, camillia, lilacs, and early petunias.
Window boxes usually feature draping plants like miniature ivies (particularly the colored varieties), ferns, as well as very small evergreens for contrast.
If it would bloom in the north of the US in March, you would find it in London as well.