Choice of rootstock

Although at one time it was a common complaint that pre-phylloxera wines are better than those since the invasion (perhaps partly because early rootstocks were not always ideally matched with soil types), more recent experiments have shown that little effect on wine quality can be attributed directly to rootstock. The effect of rootstock on wine quality is probably no greater than that of other factors such as soil, climate, fertilization, and irrigation. Certainly rootstocks can influence vigour, and the high-vigour rootstocks such as Rupestris St George can produce canopies so dense that they affect wine quality (see canopy management). Other studies indicate that the high-vigour rootstocks Harmony, Dog Ridge, Freedom, and Ramsey can result in high levels of potassium and ph in the resultant wine, but again this may be an indirect effect mediated through vigour and excessive canopy shade.