Why did Paul's mother decide to plant a citrus grove in their backyard?

I actually don't recall this. What chapter are you referring to?

I'm assuming you're referring to Edward Bloor's The Mandarin. In the book, Paul's mother wanted to create a source of income for her family, so she decided to plant a citrus orchard in her backyard. The family had recently moved to a new area in Florida, and Paul's mother wanted to start a small business to take advantage of the fertile soil and warm climate. She believed that selling oranges and other citrus fruits would provide her family with a stable income as well as connect them more closely with their new community. Also, Paul's mother was passionate about gardening and she saw the citrus grove as a way to express her creativity and love of nature.