Formal analysis of seeding and growth of crystals exhibiting spontaneous polarization has been attempted using lithium iodate (alpha-LiIO3) and barium metaborate (beta-BaB2O4) as representative materials grown from aqueous and high-temperature solutions, respectively. We suggest that the specific growth features of nonlinear optical alpha-LiIO3 and beta-BaB2O4 crystals are being determined by formation and evolutionary restructuring of a double electric layer (DEL) at the growth interface. Both composition and structure of the DEL are governed by potential-determining ions of the growth medium as well as by the nature of crystal polarization and its properties. We have found that the composition and structure of the DEL together with the magnitude and direction of spontaneous polarization of the seed (crystal) predetermine the macrotwinning boundaries during seeding and subsequent stages of crystal growth as well as the formation of microtwin structures of various sizes. Similar reasoning is applied to possible crystal asymmetry, cellular growth, extinction of growth, etc. Model concepts of seeding and growth of bulk polar crystals are discussed.