Join Parks and Recreation Department for our Annual Arbor Day Celebration! Our Parks are home to over 10,000 trees! We understand the importance and benefits that trees provide to our park users and community as a whole. Providing shade, storm water management, urban temperature regulation, and increasing property values, trees have a larger impact on our everyday lives than we often recognize. This year, we will be holding Arbor Day at Centennial Park on May 4th. The event will consist of tree plantings, educational booths for fourth graders in Billings, and planting of the official Arbor Day Tree!