Initially, trees struck Stewart as an odd thing to collect—trees being, for the most part, large and difficult to sell or tuck into a suitcase the way philatelists might their beloved stamps and brandophilestheir cigar bands. Intrigued by this community of enthusiasts, she discovered educators, preservationists and visionaries, all hooked on a kind of curation, motivated by reasons as diverse as their projects. They plant trees in public and private spaces both modest and expansive, nurturing their collections to honor beloved dead, attract wildlife, preserve rare species, connect to history, invest in the future, grow food and create beauty. “When you ask people to tell you about the one activity they do not for money, not out of necessity, but to indulge their deepest passions and their wildest curiosities,” Stewart writes, “well, you’re in for an intimate conversation.”