א אֵין לַעֲשׂוֹת סֻכָּה תַּחַת בַּיִת אוֹ אִילָן; וְהָעוֹשֶׂה סֻכָּתוֹ תַּחַת הָאִילָן, יֵשׁ אוֹמְרִים שֶׁאִם הָאִילָן צִלָּתוֹ מְרֻבֶּה מֵחַמָּתוֹ פְּסוּלָה בְּכָל עִנְיָן, אַף אִם הַסֻכָּה צִלָּתָהּ מְרֻבָּה מֵחַמָּתָהּ; אֲבָל אִם הָאִילָן חַמָּתוֹ מְרֻבָּה מִצִּלָּתוֹ, אִם הַסֻכָּה צִלָּתָהּ מְרֻבָּה מֵחַמָּתָהּ בְּלֹא אִילָן, כְּשֵׁרָה, אֲפִלּוּ לֹא הִשְׁפִּיל הָעֲנָפִים לְמַטָּה לְעָרְבָם עִם סְכָךְ הַסֻכָּה; אֲבָל אִם אֵין הַסֻכָּה צִלָּתָהּ מְרֻבָּה מֵחַמָּתָהּ אֶלָּא עַל יְדֵי הָאִילָן, צָרִיךְ שֶׁיַּשְׁפִּיל הָעֲנָפִים וִיעָרְבֵם עִם הַסְכָךְ בְּעִנְיָן שֶׁלֹּא יִהְיוּ נִכָּרִים וִיהֵא סְכָךְ רַבֶּה עֲלֵיהֶם וּמְבַטְּלָן. וְיֵשׁ אוֹמְרִים שֶׁאֲפִלּוּ אִם הַסֻכָּה צִלָּתָהּ מְרֻבָּה מֵחַמָּתָהּ בְּלֹא הָאִילָן, וְהָאִילָן חַמָּתוֹ מְרֻבָּה מִצִּלָּתוֹ, אִם עַנְפֵי הָאִילָן מְכֻוָּנִים כְּנֶגֶד סְכָךְ הַכָּשֵׁר פְּסוּלָה בֵּין שֶׁהָאִילָן קוֹדֵם בֵּין שֶׁהַסֻכָּה קָדְמָה, כֵּיוָן שֶׁעַנְפֵי הָאִילָן מְכֻוָּנִים כְּנֶגֶד סְכָךְ הַכָּשֵׁר. הַגָּה: מִיהוּ אִם הִשְׁפִּיל הָעֲנָפִים לְמַטָּה וְעֵרְבָן עִם הַסְּכָךְ, שֶׁאֵינָן נִכָּרִין, בְּטֵלִין וְהַסֻּכָּה כְּשֵׁרָה (הָרֹא"שׁ וְהָרַ"ן); וְכֵן אִם הִנִּיחַ סְכָךְ הַכָּשֵׁר עַל סְכָךְ הַפָּסוּל, מִקְרֵי עֵרוּב, וְכָשֵׁר (מָרְדְּכַי פ"ק דְּסֻכָּה). אֲבָל אִם הָעֲנָפִים כְּנֶגֶד הָאֲוִיר שֶׁבֵּין הַסְכָךְ הַכָּשֵׁר אוֹ שֶׁהַסְּכָךְ הַרְבֵּה שֶׁאֲפִלּוּ יִנָּטֵל נֶגֶד הָאִילָן נִשְׁאָר כַּשִּׁעוּר (טוּר), כְּשֵׁרָה הוֹאִיל וְצֵל הַכָּשֵׁר הוּא מְרֻבֶּה מֵחַמָּתָהּ, שֶׁאֲפִלּוּ אִם יִנָּטֵל הָאִילָן יֵשׁ שִׁעוּר בַּכָּשֵׁר לְהַכְשִׁיר; וּבְכָל זֶה לֹא שָׁאנֵי לָן בֵּין קָדַם הָאִילָן לְקָדַם הַסְכָךְ, דִּין אֶחָד לָהֶם.
1 One who makes a Sukkah underneath a tree or under a roof, containing 3 Seifim: [No Sukkah can be made under a house or a tree]. One who makes his Sukkah underneath a tree - there are those who say that if the tree's shade is greater than the sunlit area, the Sukkah is completely invalid, even if the Sukkah is shaded more so than sunlit. However, if the tree's sunlit area is greater than its shade - if the Sukkah's shade is greater than its sunlit area without a tree, it is Kosher even if the branches were not lowered to mix with the schach of the Sukkah. However, if the Sukkah is not shaded more so than sunlit because of the tree, it is necessary to lower the branches and mix the with the Shach in such a way that they are not recognizable and the Schach is the majority and nullifies it. And there are those who say that even if the Sukkah's shade is greater than its sunlit area without the tree, and the tree's sunlit area is greater than its shaded area, if the branches of the tree are aimed or directed to the kosher Shach, it is pasul (invalid), whether the tree was there first or the Sukkah was there first, when the branches of the tree are directed toward the kosher Schach. Rema: However, if the branches were lowered down and mixed with the Schach so that it is not noticeable, it is batul and the Sukkah is Kosher (the Rosh and the R"an). Similarly, if the kosher Schach rests on the invalid Schach, it is accidentally mixed and therefore kosher (Mordechai) However, if the branches are towards the air between the Schach, it is Kosher or if the Schach is the majority such that even if it is removed from the tree it retains its measure (Tur)It is Kosher inasmuch that the valid shade is greater than the sunlit areas so that even if the tree is removed there is enough valid Schach to make it kosher. In any event it does not matter whether the tree existed first or the Sukkah existed first; there is one law for both of them.