Here are some more book lists for you. Some of the lists have a focus on spring and growing things.
From the National Council of Teachers of English—Children’s Literature Assembly: 2007 Notable Children's Books in the English Language Arts
Outstanding International Books 2007 (Kathleen Isaacs—School Library Journal, 2/1/2007)
The Children’s Book Council Bimonthly Showcase for March & April 2008: Earth Day—Exploring the Natural World
Children's Books for Garden and Plant Lovers
(A Notes from the Windowsill annotated bibliography by Wendy E. Betts.)
From the Miss Rumphius Effect (March 2007): A List of Books about Seeds and Growing Things
From The Bulletin of the Center for Children's Books: Spring Will Come—A Hopeful Seasonal Dozen (Selected by Deborah Stevenson, Editor)