The largest rose ever bred was a pink rose measuring approximately 33 inches in diameter. It was bred by Nikita K. Rulhoksoffski from San Onofre, California. The world’s largest rosebush is a white Lady Banksia located in Tombstone, Arizona. Its original root came over from Scotland in 1885. From a single trunk, which is nearly six feet in diameter, it spreads over an arbor that is enough to shelter a crowd of 150 people.