Okay, so you know how some gardens have these really cool, shaped bushes and hedges? They make the garden look really fancy and interesting. Well, a bibliography is like a big list of all the books and papers that people have written about these types of plants.
Basically, people who know a lot about gardening have studied and written about how to make bushes and hedges into different shapes and designs. They might write about what kind of plants work best for making a certain shape, or how to take care of the bushes so they stay looking nice.
When they write about these things, other people who like gardening can read what they wrote and learn from it. So, a bibliography of hedges and topiary lists all the books and papers where people have written about these cool shaped bushes. That way, someone who wants to learn more about them can look at the list and find things to read!