Between 1921 and 1943 Dexter carried on a massive breeding program at his 76-acre estate in Sandwich, Massachusetts. There he developed between 5,000 and 10,000 seedlings annually and gave thousands of plantings away to private gardens, nurseries and public botanical collections.
His estate is now operated as the Heritage Museums and Gardens which contains plantings of 125 of the known 145 Dexter cultivars.