In addition to ripeness levels, the harvest yields can also have a strong influence in the resulting quality and flavors of Cabernet Sauvignon wine. The vine itself is prone to vigorous yields, particularly when planted on the vigorous SO4 rootstock. Excessive yields can result in less concentrated and flavorful wine with flavors more on the green or herbaceous side. In the 1970s, a particular clone of Cabernet Sauvignon that was engineered to be virus free was noted for its very high yields-causing many quality conscious producers to replant their vineyards in the late 20th century with different clonal varieties. To reduce yields, producers can plant the vines on less vigorous rootstock and also practice green harvesting with aggressive pruning of grape clusters soon after "veraison".