“Chanticleer” is the whimsical creation of Adolph Rosengarten Jr. and his father, heir of a chemical and pharmaceutical business who managed its merger with Powers and Weightman to create the vast conglomerate that led to the present Merck and Co. From its origins as a gentleman's estate with a gracious French-tinged country house at its center, the now thirty-one-acre property includes Andrew Borzner's house for E. T. Stuart (1925). Named for Chaucer's mythic rooster, whose image is repeated around the grounds, the estate has been transformed into a changing kaleidoscope of gardens, each merging art and horticulture. Though accomplished on a framework established by the original landscape of Willing, Sims and Talbutt (better known for their Chestnut Hill estates) and the ubiquitous Thomas Sears, the gardens have taken on an edgy, contemporary design quality under the direction of horticulturalist Howard Holden and, later, Chris Woods that sets them apart from the usual gentleman's hobby.