Since their first visit, Tom and Phyllis McCasland have considered the Dallas Arboretum a unique and special place. This affinity for the Garden is evident in their commitment to see the continued expansion of the Arboretum by funding the McCasland Sunken Garden, which opened March 2006.

The garden, designed by Warren Johnson of Fallcreek Gardens, is a renovation and upgrade of the original Sunken Garden. When entering from the DeGolyer or south entry, visitors are greeted by a procession of Italian jardinières and geometric patterns shaded by towering trees. The central aisle steps down to the sunlit grass court's congregational space.