To keep up a mixed stock of even such extremely close varieties as the variously coloured sweet-peas, they must be each year harvested separately, and the seed then mixed in due proportion, otherwise the weaker kinds will steadily decrease in number and disappear.
Multzo nahasi bat erdiesteko, kolore askotako ilarrena moduko aldaki hurbilena izanik ere, fruitua bereiz bildu behar da urtero eta gero haziak behar den proportzioz nahasi; bestela, mota ahulenak gutxitu eginen lirateke beti eta ezabatu.