Commentaire sur Le Deutéronome 33:13

מברכת ה' ארצו BLESSED OF THE LORD BE HIS LAND — It is a fact that there was in the inheritance of all the tribes no land so full of every good thing as Joseph's land (Sifrei Devarim 353:1).

MIMEGED’ OF HEAVEN. “Meged is an expression for dainty food and sweets. 14. ‘UMIMEGED’ OF THE FRUITS OF THE SUN — for Joseph’s land was exposed to the sun and it sweetened the fruit. ‘GERESH YERACHIM’ (THE YIELD OF THE MOONS). There are fruits which the moon ripens; they are cucumbers and melons. ‘Geresh yerachim’ — fruits which the earth ‘puts forth’ and produces ‘from month to month.’” This is Rashi’s language. And if so, with ‘pri m’gadim’²⁰⁷Song of Songs 4:13. will mean “with sweet fruits.” Thus Moses blessed Joseph that his land would benefit from the sweetness of heaven which will be from the dew, and that it would be blessed from the deep that couches under his land, becoming fountains and depths, springing forth in valleys and hills.²⁰⁸Above, 8:7.
It is possible that the fruits [themselves] are called m’gadim,²⁰⁹According to the first interpretation meged shamayim means “the sweetness of the heaven.” According to this second explanation, meged shamayim means “the fruits of the heaven.” Both express that the reference is to the dew of heaven. and he thus says that “Joseph’s land is blessed of the fruits of heaven, namely the dew” — since sweet fruits result from dew, therefore the fruit is called meged — “and his land shall also be blessed from the deep beneath.” Moses’ blessing is similar to that of Jacob who said, with blessing of heaven above, blessings of the deep that coucheth beneath.²¹⁰Genesis 49:25. And the meaning of geresh yerachim is the fruits which are given forth month by month, for all trees blossom and bud in their [respective] seasons that they might bring forth branches, and that it might bear fruit.²¹¹Ezekiel 17:8. This is the sense of the verse, it shall bring forth new fruit every month,²¹²Ibid., 47:12. meaning that in the particular months a certain fruit will become timely before [the fruits of] all other trees.

מבורכת ה' ארצו, Moses explains that the lands given to the tribe of Joseph are naturally fertile, blessed by G’d.