The flora of Gillies Hill is intricately entwined with its history. The Murray family who built Polmaise Castle in 1865, created landscaped gardens incorporating many of the exotic coniferous trees that still grace the woodland. Like much of 19th Century British aristocracy, the Murrays were enamored with planting landscape gardens filled with newly discovered plants from around the world. Often these outdoor plant collections included tall conifers imported from North America. A fine example of this is the grove of Sierra Redwoods (or Wellingtonia), Sequoiadendron giganteum, growing at the apex of Gillies Hill. These five Redwoods were planted in the 1860s by the Murray family along the walk from the castle to the large natural loch that was once on the upper portion of Gillies Hill, but was lost to quarrying. If left undisturbed, these giants could well live over 3000 years and attain a mass of over 1400 cubic meters potentially becoming the most massive trees in Scotland. Along with others of that era, these trees may have been grown from some of the first Sequoiadendron seeds brought to Scotland by John D. Matthew in 1853 and given to his noted horticulturist father Patrick Matthew of Gourdiehill near Errol in Perth Shire who then gave many of the seedlings away to friends and family as living gifts.