Genesis 30:14

And Reuben went in the days of Sivan, in the time of wheat harvest, and found (Yaveruchin) mandrakes in the field; and he brought them to Leah his mother. And Rahel said to Leah, Give me now of thy son's mandrakes.

‘DUDA’IM.’ These are ‘sigli’ (violets). In Arabic it is called jasmin. So I found in Rashi’s commentary. But this is not so for the Arabic jasmin bears the same name in the words of our Rabbis, as they say in the chapter Bameh Tomnin: “Poppy pomace flavored with jasmin may be used [as a lotion on the Sabbath],” while they say sigli is an odorous herb concerning which they have said that on smelling it, one recites the blessing: “Blessed art Thou… who createst odorous plants.” However, their season is not in the days of the wheat, but perhaps Reuben found them there by chance. It is best to accept Onkelos’ opinion concerning the translation of duda’im, which he rendered as yavruchin (mandrakes). In Bereshith Rabbah it is also explained similarly: “Rabbi Chiya the son of Rabbi Abba said, ‘Yavruchin,’” and these are yavruach in Arabic.
Now Rabbi Abraham ibn Ezra wrote: “Onkelos translated duda’im as ‘mandrakes,’ and so they are called in Arabic. They have a good odor. And it is so written: The mandrakes give forth fragrance. They resemble the human form as they have the shape of the human head and hands. Now some say that they are an aid to pregnancy, but I do not know it since their effect is to produce the cold fluid in the body.” These are Ibn Ezra’s words.
The correct interpretation is that Rachel wanted the duda’im for delight and pleasure, for Rachel was visited with children through prayer, not by medicinal methods. And Reuben brought the branches of duda’im or the fruit, which resemble apples and have a good odor. The stem, however, which is shaped in the form of the human head and hands, he did not bring, and it is the stem which people say is an aid to pregnancy. And if the matter be true, it is by some peculiar effect, not by its natural quality. But I have not seen it thus in any of the medicinal books discussing mandrakes.

דודאים, flowers of the fig tree; (compare Jeremiah 24,1) In Song of Songs 7,14 these flowers are described as rich in fragrance.

וילך ראובן, when he saw that his mother was unhappy that she was no longer having children,

וימצא דודאים, a pleasant smelling herb, the fragrance stimulating the human organs related to conceiving and giving birth. Our sages (Baba Kamma 82) said garlic has a similar effect on people and that this is the reason why one eats garlic on Friday nights when the husbands cohabit with their wives. The Dudaim appear to have been known as producing a similar effect. It is possible that the Dudaim had an even better effect in stimulating the feelings of love between a man and his wife. This idea is based on Song of Songs 7,13-14 שם אתן את דודי לך, הדודאים נתנו ריח, “there I will give my love to you, the mandrakes yield their fragrance.” Our verse would testify both to Reuven’s righteousness and his intelligence. especially considering that at that time he could hardly have been older than 4 or five years old.

וילך ראובן, Reuven was about 6 or 7 years old at the time. He went out into the wheat fields, found these dudaim and brought them to his mother Leah. Dudaim are a kind of herb whose roots have a natural reddish appearance. Perhaps Reuven had heard some place that this herb is supposed to help women get pregnant, and that seeing his mother had not had any babies lately, he meant to help her in this regard. The popular belief in the efficacy of the dudaim in this respect is not based on fact. If it had been true, why did Rachel not get pregnant after eating them? Also Leah did not get pregnant as a result of eating dudaim, for the Torah says: וישמע אלוקים אל לאה, that G’d listened to Leah’s prayer. (verse 17)

ותאמר רחל, she was under the impression that the popularly held belief about dudaim was correct.