Why are Wrigley Field's outfield walls covered in ivy?

Wrigley Field, Chicago Cubs ballpark - Ballparks of Baseball

73 Ivy Wall Wrigley Stock Photos, High-Res Pictures, and Images - Getty Images

Looking Back: 100 Years at Wrigley Field

Chicago Celebrates A Century Of Baseball At Wrigley Field : NPR

Wrigley Field Photo Print Wrigley Field Ivy Wall Chicago

Chicago Cubs - #CubsCollection: Ivy. The historic ivy has adorned the outfield walls of the Friendly Confines since 1937. Originally English ivy, now primarily Boston ivy, the vining plant was added to

The Wrigley Field Ivy And The New Left-Field Wall - Bleed Cubbie Blue

Left field wall at Wrigley Field without the Ivy. They're doing brick maintenance. : r/baseball

Origin of Wrigley Field ivy

478 Wrigley Field Wall Stock Photos, High-Res Pictures, and Images - Getty Images

Wrigley Field Fills Fans With Reverence, Even if It Looks a Bit Less Friendly - The New York Times

Ivy at Wrigley Field? It was snatched from Indy

Why are Wrigley Field's outfield walls covered in ivy?

Chicago Illinois September 8 368 Feet Stock Photo 215925454