This Poison Heart by Kalynn Bayron

Briseis has a gift: with a single touch, she can grow plants from tiny seeds to rich blooms.

When Briseis’s aunt leaves her a dilapidated estate, Bri and her parents head there for the summer. Hopefully surrounded by plants and flowers, Bri will finally learn to control her gift. But their new home is sinister in ways they never imagined--it comes with a specific set of instructions, an old-school apothecary, and a walled garden growing the deadliest botanicals in the world.