The Poison Diaries — Maryrose Wood

In the right dose, everything is a poison. Even love . . .
Jessamine Luxton has lived all her sixteen years in an isolated cottage near Alnwick Castle, with little company apart from the plants in her garden. Her father, Thomas, a feared and respected apothecary, has taught her much about the incredible powers of plants: that even the most innocent-looking weed can cure -- or kill.

When Jessamine begins to fall in love with a mysterious boy who claims to communicate with plants, she is drawn into the dangerous world of the poison garden in a way she never could have imagined . . .