The farming area known as Golden Mile is home to six percent of the total planted vineyard acres in the Okanagan/Similkameen. For the most part, vineyards are sited on fluvial fan soils unique to the valley as they are a result of erosion from the mountains to the west and this locale. Most valley soils originated from northern and central BC, arriving with the last glacial episode.
Ratnip soils are mostly dark brown, stony, gravelly sandy loams or gravelly loamy sands. In addition to the Oliver area, Ratnip is a soil that also occurs in Summerland and East Kelowna. Ratnip soils are suitable for most agricultural crops, yet steep topography along with stoniness can be limiting in some areas. The native vegetation is sagebrush and grasses, with Ponderosa pine and Douglas fir. Ratnip soils drain rapidly and have low to moderate water-holding capacity.
Stemwinder, a dark greyish-brown soil commonly found in the Similkameen Valley, is also found near Oliver, Penticton and Peachland. Stemwinder soil has a gravelly, moderately coarse texture that overlies gravel and stone. Surface textures range from gravelly loam to very sandy loam. Native vegetation includes sagebrush, grasses and Ponderosa pine. Like Ratnip it drains rapidly and has moderate to low water-holding capacity.
Ponderosa soil only occurs in the Oliver area. Ponderosa soil is dark greyish brown gravel over-laid with sandy loam. While most of the Ponderosa soils are cultivated, any uncleared areas support Ponderosa pine, sagebrush and grass. These soils drain rapidly and have low water-holding capacities.
These three soil types are all very different but to the layman the distinctions are quite small. They differ in their mineral content and are essentially variations on loamy, gravelly sand. The soil types are gradations of the same elements which result in distinctly different mineral content with distinctly different flavours imparted into the grapes.