The designed landscape at Ardgowan was laid out c.1800 to the designs of James Ramsay.
The lands of Ardgowan were conferred by Robert III in 1403 to his natural son, Sir John Stewart, whose descendants have held the lands of Ardgowan ever since. The old castle at Ardgowan is now a ruin and lies a short distance to the south-west of the present mansion. The designed landscape at Ardgowan dates from the end of the 18th century when the new mansion house was built. The 3rd Baronet, Sir Michael, had married Helen Houston in c.1730, an heiress of the Shaw family and acquired the Mansion House in Greenock. His son, John Shaw- Stewart, commissioned Hugh Cairncross to design a new mansion house at Ardgowan which was started in 1797. John's wife, Frances, was the widow of Sir James Maxwell, 6th Baronet of Pollok, who was herself a keen gardener and is reputed to have introduced shrubs and the snowdrops, for which Ardgowan is renowned, from Pollok.
The design plan for the layout of the grounds around 1800 has recently been discovered at Ardgowan. It is by James Ramsay, and a survey plan of 1817 drawn by D. Reid, also kept at the house, shows the landscape laid out according to Ramsay's plans, with minor changes, eg the drives. The 6th Baronet, Sir Michael, succeeded in 1825 and employed William Burn to carry out additions to the house. He was succeeded by his son, Sir Michael, as 7th Baronet in 1836 and he married Lady Octavia Grosvenor in 1852. They made many improvements to the grounds and Lady Octavia brought her gardener from Eaton Hall in Cheshire to Ardgowan. A formal garden was laid out to the south west of the house with a beech walk along the ridge to the Castle. Two summerhouses were placed along the woodland walks in the grounds. The formal garden was laid out with white gravel paths.
Sir Michael died in 1903 and was succeeded by Sir Hugh, who employed Lorimer in 1904 to carry out improvements which included the construction of the Conservatory. Sir Hugh married Lady Alice Thynne who was a keen plantswoman and kept detailed record books of the gardens. They were both keen planters; the policy woodlands were planted up to be viewed from the house and exotic and ornamental trees and shrubs were planted along the ridge. The Golden Garden was added for them on their Golden Wedding Anniversary. During World War II the house was used as a hospital and some of the garden features, such as the summerhouses, were lost during this time.
Sir Houston and Lady Shaw-Stewart are currently making improvements to the gardens and have commissioned Vernon Russell Smith to design the new layout along the south-west front of the house.