Soils & Microclimate
The soils at O'Neill Vineyards and Maloy O'Neill Vineyards are similar in structure but differ in many ways. They are both primarily Arbuckle-Positas San Ysidro complex. Maloy O'Neill Vineyards is primarily loam's and sandy loams, and O'Neill Vineyards is mostly coarse loam with clay and chalky areas. Both properties are in the Huero Huero River area and have daily summer temperature fluctuations ideal for grape growing. Average yearly rainfall is anywhere from 8-15 inches. The Paso Robles Viticultural Area is typified by rolling hills and valleys with an average elevation between 600 and 1,900 feet. The Santa Lucia Range, whose crests average 2,300 to 2,800 feet in elevation, protects it.
The soils are generally alluvial and terraced deposits. Soils are fertile and well drained also providing for ideal grape growing conditions. The area is classified as Region II which is 2,501 to 3,500 degree-days of heat. The days are hot and the nights are cooled by the marine layer that moves into the area like clockwork at sunset. It is not uncommon to have a 50-degree change in temperature per day. This is the reason Paso Robles is so desirable for premium wine grape production. Warm to hot days and cool nights promotes excellent sugar acid balance in wine grapes. This is reflected in many of the great wines coming out of this area.