Mary Lennox's physical and emotional growth in The Secret Garden parallels the growth of the secret garden itself. At the beginning of the book, when she lives in India, Mary is described as "the most disagreeable looking child ever seen" (page 3). In addition to looking horrid, she is also described as "sickly" and "fretful." Ignored by her parents and placated by her servants, she has very rude behavior and refers to her servant as a "pig" (page 3).
After her parents die and she is sent to her uncle's house in Yorkshire, England, Mary begins to become less contrary. Martha, the maid at her uncle's house, treats Mary in a kind but disciplined way that does Mary good. Burnett writes about Martha, "there was something comforting and really friendly in her queer Yorkshire speech and sturdy way that had a good effect on Mary" (page 15). Mary spends all day playing outside, and "when she sat down to her supper at night she felt hungry and drowsy and comfortable" (page 25). She grows less cross and healthier in her body. Over time, she develops sympathy and befriends a robin. She says to the robin, "Would you make friends with me" in a voice that is "soft and eager and coaxing" (page 22). This tone of voice is new to her, and the robin eagerly befriends her.
Mary later befriends Colin, an ill boy she hears crying in her uncle's house. Colin turns out to be her cousin, and he cannot walk well. Instead of being rude to him, as was her tendency in the past, she turns to keeping him company. Eventually the two children wander into the secret garden that their uncle keeps locked. Mary and Marta take Colin there to help him get stronger. Mary also tends to the care of the garden, just as she tends to the care of Colin. As the garden grows, so also do Mary and Colin grow towards emotional and physical health.