E. T. Cook, Trees and Shrubs for English Gardens
“ Many grow their plants in pots, the general method being what may be regarded as a modification of pot culture and planting out, that is to say, although the plants are potted, and that in fairly large pots, they are plunged in the open ground over the rim of the pot, and in a position fully exposed to air and sunshine. Although a few roots may be pushed out over the rim, and also through the hole in the bottom, this treatment has the effect of keeping them far more compact than would otherwise be the case, hence the check of removal is not so great as if they have unlimited room. ”
