Polk County is a county-level American Viticultural Area (AVA) in the center of the Willamette Valley in Oregon. The cool climate in the county is well suited to the production of bright, fruit-forward red wines made from the Willamette Valley favorite, Pinot Noir.
Polk County lies to the south of Yamhill County and just west of Oregon's state capital of Salem. The AVA is home to most of the Eola-Amity Hills sub-region in the north-eastern corner of the appellation, and a few other vineyards can be found scattered around the landscape to the south, mostly in the foothills of the Coastal Range. Interestingly, the Willamette Valley AVA covers only the eastern half of Polk County; the land in the coastal mountains is considered unsuitable for viticulture.
The Van Duzer Corridor, a gap in the mountains, is located at Polk County's northern border and brings cooling winds into the AVA from the Pacific Ocean 30 miles (50km) away. As a result, the vineyards of Polk County are cooler than those in the northern reaches of the Willamette Valley, where there is more shelter from the prevailing winds. The growing season in Polk County is longer, and vineyards are usually planted on south-facing slopes to maximize sunlight exposure. The increased diurnal temperature variation during the growing season is important for the development of acidity, leading to balanced wines with complex flavors.
There is a variety of soil types within Polk County, from fertile silt on the valley floor to weathered basalt and sedimentary soils on the higher slopes. Most vineyards prefer the poorer-quality soils on the Eola-Amity Hills, and the red, volcanic soils here known as Jory are excellent for viticulture. These iron-rich, well-drained soils stress the vines, causing them to focus their resources on producing high-quality berries instead of leafy foliage.
Polk County is not as developed viticulturally as Yamhill County in the north, and as a consequence many producers here prefer to label their wines under either the smaller Eola-Amity Hills AVA or the larger Willamette Valley AVA titles. While Pinot Noir dominates the area, there are also plantings of Riesling, Chardonnay and Pinot Gris.