אורח חיים תרמ״וOrach Chayim 646

Se’if 1א׳

הֲדַס שֵׁנִּקְטַם רֹאשׁוֹ, כָּשֵׁר; נָשְׁרוּ רֹב עָלָיו, אִם נִשְׁתַּיְּרוּ שְׁלֹשָׁה עָלִין בְּקֵן אֶחָד, כָּשֵׁר.

The Laws of the Hadas (Myrtle), 11 Seifim: If the myrtle's head is severed, it is valid. If most of its leaves fell off but three remain on one stem, it is valid.

Se’if 2ב׳

הָיוּ עֲנָבָיו מְרֻבּוֹת מֵעָלָיו, אִם יְרֻקּוֹת, כָּשֵׁר; וְאִם אֲדֻמּוֹת אוֹ שְׁחֹרוֹת, פָּסוּל; וְאִם מִעֲטָן, כָּשֵׁר; וְאֵין מְמַעֲטִים אוֹתָם בְּיוֹם טוֹב, לְפִי שֶׁהוּא כִּמְתַקֵּן; עָבַר וְלִקְּטָן, אוֹ שֶׁלִּקְּטָן אֶחָד אֶחָד לַאֲכִילָה, הֲרֵי זֶה כָּשֵׁר. וּמִיּוֹם רִאשׁוֹן וָאֵילָךְ, כָּשֵׁר בְּכָל עִנְיָן (בֵּית יוֹסֵף בְּשֵׁם א"ח).

If its berries outnumbered its leaves and they are green, it is valid. If they are red or black, it is invalid. If their numbers were diminished, it is valid, though we do not diminish them on Yom Tov because it is considered fixing. If one sinned and picked [the berries] or one picked them off one a time to eat them, it is valid. And after the first day, they are valid in any event (Beit Yosef in the name of the Orkhot Hayyim).

Se’if 3ג׳

עֲנַף עֵץ עָבוֹת הָאָמוּר בַּתּוֹרָה, הוּא הַהֲדַס שֶׁעָלָיו חוֹפִין אֶת עֵצוֹ; כְּגוֹן שְׁלֹשָׁה עָלִין אוֹ יוֹתֵר, בְּגִבְעוֹל אֶחָד; אֲבָל אִם הָיוּ שְׁנֵי הֶעָלִים בְּשָׁוֶה, זֶה כְּנֶגֶד זֶה, וְהֶעָלֶה הַשְּׁלִישִׁי לְמַעְלָה מֵהֶם, אֵין זֶה עָבוֹת אֲבָל נִקְרָא: הֲדַס שׁוֹטֶה. הַגָּה: וּפָסוּל אֲפִלּוּ בִּשְׁעַת הַדַּחַק; וְאִיכָּא מָאן דְּאָמַר בַּגְּמָרָא דְּכָשֵׁר; וְעַל כֵּן נוֹהֲגִין בְּאֵלּוּ הַמְּדִינוֹת לְכַתְּחִלָּה לָצֵאת בְּאֵלּוּ הַהֲדַסִּים הַמּוּבָאִים וְאֵין ג' עָלִין בְּגִבְעוֹל אֶחָד; וְיֵשׁ מִי שֶׁכָּתַב דַּהֲדַסִּים שֶׁלָּנוּ אֵין נִקְרָאִים הֲדַס שׁוֹטֶה, הוֹאִיל וְהֵם שְׁנַיִם עַל גַּב שְׁנַיִם וְאֵינָן כַּהֲדַס שׁוֹטֶה הַמֻּזְכָּר בַּגְּמָרָא; וְלָכֵן נָהֲגוּ לְהָקֵל כְּמוֹ שֶׁכָּתַב מַהֲרִ"י קוֹלָן וּמַהֲרִ"י איסרלן זַ"ל בִּתְשׁוּבוֹתֵיהֶם.

"Boughs of a dense-leaved tree" [Leviticus 23:40] talked about in the Torah are myrtle whose leaves cover its tree, with three or more leaves from one node. However, if there are two leaves at the same level, one opposite the other, and a third one above them, this is not considered dense; rather, it is considered wild myrtle. Rema: And it is valid, even in an emergency. There is an opinion in the Gemara that it is valid. That is why in these countries, we initially use these myrtles that are imported and do not have three leaves from one node. There is one who says that our myrtles are not considered wild myrtle because they are two by two and are not like the wild myrtle in the Gemara. Therefore, our practice is to be lenient, following what was written by Mahari"i Kolon and Mahar"i Iserlin z"l in their responsa.