The story opens by describing a neighborhood in Brooklyn, New York, called Williamsburg. There is a certain kind of tree that grows throughout the neighborhood, called the Tree of Heaven by some, since it grows wherever its seeds land—in old lots, trash heaps, and even cement. It grows only in the tenement districts, where the poor people live.
Francie Nolan has such trees in her yard in Williamsburg. The story opens on a Saturday, which always means a trip to the junkie for eleven-year-old Francie and her brother, Neeley. Carney the junkie pays the neighborhood kids pennies for the bits of tin foil and other metals that come from such junk as cigarette packs and jar lids. He likes girls better than boys, and so Francie delivers the junk for herself and her brother. She earns sixteen cents and a "pinching penny"—the extra penny Carney gives if a girl doesn't shrink when he pinches her cheek. Neeley handles the money, taking out half for the tin-can bank; the rest they divide evenly, except that Francie always keeps the pinching penny.
The two children then make their way to Cheap Charlie's, the penny candy store. Francie doesn't go inside, adhering to the unwritten rule that it is a boys' store. Here the children pay a penny to draw a number for a prize. Francie has never heard of anyone getting the good prizes-roller skates or baseball mitts or dolls. After accompanying her friend Maudie Donavan to Gimpy's candy store, she goes on to the five and dime, where she is privileged to touch the merchandise because she is buying, and decides on five cents worth of pink and white peppermints. Francie walks back home, noticing the pushcarts and smells of her neighborhood. She muses that Jewish women must have so many babies because they are hopeful that one will be the messiah, and that Irish women just looked ashamed at being pregnant.
Katie Nolan, Francie's mom, arrives home soon after her daughter, having finished her week's work scrubbing floors. She is slight and pretty and fun. The narrator also mentions that Francie's father has a drinking problem. Francie's mother sends her out to buy bread and tongue, and at Francie's pleading, sweet buns for dessert, since it is Saturday.
Francie meets up with Neeley and they return home to have lunch with Mama. Coffee is a luxury in the Nolan household, and each member of the family is allowed three cups per day, with milk. Katie Nolan believes that Francie is entitled to throw her cups down the drain, if she wishes, saying that it's good for poor people like them to be able to waste something.
After dinner, Mama sends Francie back for bread from Losher's, where the stale loaves are sold to the poor. While Francie is waiting, she stares at an old man and is suddenly frightened by his disfigurement, especially his feet. Francie then fights the crowd, and buys her bread. Once outside, she sees a baby and imagines its foot as an old person's foot, and panics again.
Francie then follows Neeley and his friends to the baseball lot, even though they don't want her along. On the way to the field, the boys stop to harass a Jewish boy. He is ultimately amazed that they thought him mature enough to be interested in girls. After he leaves, Neeley says that the kid is a "white Jew," although his friends don't believe such a thing exists. The boys then begin to harass another little boy selling pretzels, but his mother yells out the window, intimidating them.
After watching the boys play for awhile, Francie walks back to the library, where the librarian should be returning from lunch.
Although the library is small and shabby, Francie thinks it looks beautiful. She loves to read, and wants to read all the books in the world, in alphabetical order. She is in the B's right now. She treats herself on Saturdays to a book outside of the sequence, asking the librarian for a recommendation. In the library, Francie loves looking at the brown jug holds different greenery for different seasons; now it holds nasturtiums, signifying summertime. She dreams to one day have a brown bowl with flowers and lots of books.
The librarian hates children and recommends the same two books every Saturday. This time she recommends If I Were King, by McCarthy. Francie takes this and a book by Brown home. She prepares her peppermints in a bowl, and a cup of ice water and sits out on the fire escape in the middle of the trees to read. It is a sunny afternoon, and the boy who usually plays downstairs is away. He plays a game of graveyard, where he digs holes for live insects and accompanies the ceremonies with fake sobbing. Francie is glad to find him gone. Francie loves her story and dreams of owning a real book.
While on the fire escape, she observes her neighbors in the windows. Mr. Fraber's horse and wagon comes home eventually, driven by Frank, a nice young man who all the girls love. The small maroon wagon is an advertisement for Dr. Fraber's dentistry practice, and Frank's job is to drive slowly through the streets, pulling this moving billboard. Frank begins to clean the horse, Bob, with great care.
Flossie Gaddis, who lives beneath the Nolans, comes out to flirt with Frank, who is uninterested, and refuses to go out with her. Francie feels sorry for Flossie, and contrasts her with Francie's Aunt Evy, who is more successful chasing after men.
Johnny Nolan, Francie's father, arrives home singing his favorite ballad, "Molly Malone," as he always does coming up the stairs. Francie irons his apron, as he has a job singing and waiting tables that night. He wants her to sew the Union label on his apron, saying how much he believes in the Union, and that Katie Nolan shouldn't begrudge the wages.
Francie loves listening to him talk, and reminisces about visiting the Union Headquarters, where she saw how popular her father was, but also overheard two men talking about Johnny's drinking habit.
Everyone loves Johnny, who is Irish and sings sweet songs. His wife had not grown bitter toward him and his children "didn't know that they were supposed to be ashamed of him."
Back at their flat, Johnny talks and talks about his lack of a job and his family's growing up. His words make Francie alternatively happy and hurt. She agrees with her father that her mother is a very good woman, but then wonders to herself why she likes her father better. He talks to Francie about winning horse bets and going on trips, and calls her Prima Donna, a nickname he gave her when she was an infant when her crying reminded him of an opera singer's voice. He then sends her out for a dicky and a paper collar, two pieces to go with his tuxedo. He is clean, and dressed well—like an Irish lad, but not like a man who has two poor children, and a wife who scrubs floors. Francie walks him to the trolley and thinks him very handsome.
The first few paragraphs of Chapter 1 introduce the most important symbol in the book—the tree referred to in the title. The tree represents hope in the midst of hardship; the narrator writes that it "likes poor people." Specifically, it symbolizes the lives of the poor in Francie's neighborhood in Brooklyn, New York. The fact that this tree also grows in Francie's yard suggests that it symbolizes her life as well. Just as the tree grows with no light or soil, Francie will grow up strong despite living with few material advantages.
The first few chapters (along with the title) establish the importance of setting in this novel. In fact, in just the first chapter, the narrator describes the entire neighborhood through Francie's eyes, on a typical Saturday afternoon, including many of the neighborhood personalities and places: Carney and his junk shop, Cheap Charlie's, and all the different food stores. In this novel, the setting is more than a mere backdrop for the action; it defines much of Francie's character development, and shapes her into the kind of person she is. These chapters also set the stage for a coming of age narrative by describing the world Francie lives in, and how she sees herself in that world.
Religious and national identity will also be major forces in Francie's upbringing. In the first chapter, she already observes the differences between pregnant Catholic women and pregnant Jewish women. The narrator notes that the Jewish delicatessen is filled with Christians buying rye bread. When Neeley and his friends go to play baseball, they harass the Jewish boy, and then embark on a theological discussion of whether or not "white Jews" exist. This religious marking suggests that religious identities are important differences to the characters in the story.
Francie's trip to the library allows the author to develop her character further. Francie sees the library as beautiful even though it is a shabby old building; she loves books so much that she wants to read every single one in the world, and is only a little discouraged that some take awhile to plow through; she notices with glee what kind of flora is in the old brown pot, and rejoices that the little nasturtium blossoms mean that it is summer. All in all, Francie is a character who will take great pleasure in the small material things in her life. Her childlike wonder is magnified by her economic status: because she is afforded few luxuries, she appreciates each tiny beautiful thing that comes her way. She is a keen observer. She reads her book on the fire escape so that she can observe her neighborhood below. Frankie coming home with Mr. Fraber's wagon is a big event; the absence of the boy who conducts mock funerals is reason for great rejoicing.
Flossie Gaddis, as a teenage girl, is a representation of adolescent life that Francie will one day enter. Flossie is one image of what Francie may become—her family lives in Francie's building, which suggests that their situation is similar. Already Francie observes different models of adulthood, when she compares Aunt Sissy to Flossie; whereas Flossie is "starved" for men, Sissy was "healthily hungry" for them.
The third chapter of the novel introduces Johnny Nolan. Johnny is not a conventional good father. Women think Johnny a dapper young lad—outfitted in his tuxedo and projecting a charming happy-go-lucky attitude—until they realize he has a hungry daughter and a wife who makes up for his drinking weakness. Johnny dramatizes the moral code in the book over and over again. He is both worthless when it comes to money and loving, both charming and weak. When all is said and done, Johnny is still a good person. The book shows that people can have faults and still be good; Francie loves him dearly, even when she grows older and knows her family has suffered as a result of his undependability.