Start with high-confidence science & nature books, then narrow by subgenre or adjacent topics.
Tap the Magic Tree
Christie Matheson
Plant the Tiny Seed Board Book
The Digger and the Flower Board Book
Joseph Kuefler
Planting a Rainbow Board Book
Lois Ehlert
Toot & Puddle: How Does Your Garden Grow?
Holly Hobbie
How to Say Hello to a Worm
Kari Percival
Baby Botanicals: Good Morning, Garden!
Jillian Miao
Baby Botanicals: Peekaboo, Flowers!
The Carrot Seed Board Book: 75th Anniversary
Ruth Krauss
A Seed Grows
Antoinette Portis
Grow
Riz Reyes
Seed to Plant (national Geographic Kids Readers, Level 1)
Kristin Baird Rattini
Up in the Garden and Down in the Dirt
Kate Messner
