Taken from the website:
"Located at the base of the 7 1/2 acre Mountainside Park, the iris gardens contain over 10,000 irises of approximately 1,500 varieties and produce over 100,000 blooms over the course of the season. Visitors can see by the arching slope of the garden beds why Presby is often referred to as the “rainbow on the hill”.

The Presby Iris Gardens were established in 1927 in memorial of Frank Presby and are now one of the largest collections of iris in the world. Presby was a founding member of the American Iris Society and its first treasurer. The Iris Gardens are open only in spring and autumn, for obvious reasons, and are then spectacular."