Genesis 30:14

“And Reuben went in the days of wheat harvest, etc.] Leah’s eldest son, who is supposed to be at this time about four or five years of age f1492, who went out from the tent to the field, to play there perhaps; and this was at the time of wheat harvest, in the month Sivan, as the Targum of Jonathan, which answers to part of our May; a time of the year when the earth is covered with flowers: and found mandrakes in the field; the flowers or fruit of mandrakes, mandrake apples, as the Septuagint. This plant is said to excite love, provoke lust, dispose for, and help conception; for which reasons it is thought Rachel was so desirous of these “mandrakes”, which seem to have their name “dudaim” from…”

“30:14-17 Mandrakes were considered an aphrodisiac and aid to procreation (see Song 7:13). Rachel thought they would help her get pregnant, so she traded Jacob for a night to get them. In the process, Leah got pregnant, not Rachel.”