historically, massal selection was the primary means of vineyard propagation, particularly in traditional vineyards where vines are only sporadically replaced, often by layering a cane from a neighboring vine. in the 1950s, the isolation and identification of desirable clones in nurseries and breeding stations lead to an increase in clonal selection with new vineyard plantings seeking out clones from well established vineyards and wine region. this trend towards clonal selection has seen some criticism from wine writers and viticulturalists who complain about "mono-clonal" viticulture that has the risk of producing wines that are overly similar and dull.