Sukkah, Chapter 3, Mishnah 2. Our Mishnah discusses the qualities required in the hadas - the myrtle branch, of which we take three for the mitzvah of the four species. Many of the disqualifications listed in the first Mishnah of our chapter appear here again with regard to the hadas.
The disqualifications identical to those taught in the previous Mishnah:
"Hadas hagazul" - a stolen myrtle is invalid, because the Torah says "lachem," that it be yours; and even if it has come into his possession, it comes by way of a transgression - a mitzvah fulfilled through a sin - and therefore it is invalid.
"Vehayavesh" - a dried out myrtle is invalid, because "hadar" is required of it, that it possess a certain measure of its natural beauty, and in a dried out myrtle that beauty is no longer present.
"Shel asherah veshel ir hanidachas" - an asherah is a tree that was worshipped as idolatry, and an ir hanidachas is a city in which the majority of the inhabitants worshipped idolatry. In both cases the object is designated for burning, and since it stands to be burned, it does not have the required measure for fulfilling the mitzvah, and therefore it is invalid.
"Niktam rosho" - its top was cut off.
"Nifretzu alav" - its leaves were stripped off.
The disqualification unique to the hadas - "shehayu anavav merubos me'alav":
This is a feature unique to the hadas. Myrtles sometimes grow small berries, which the Mishnah calls "anavim," grapes. It does not mean actual grapes, but those small berries. If the number of berries exceeds the number of leaves, the hadas is invalid.
The Gemara explains that the berries present a problem only when their color is black or red, and then they disqualify the hadas. But if they are still green, like all the other leaves, they blend in with them, and the hadas is valid.
"Umi'atan - kasher":
Even when the berries are of the disqualifying type, that is, red or black, the invalidity is not absolute. Since the disqualification depends on the berries outnumbering the leaves, if one reduces their quantity and picks them off until they are fewer than the number of leaves, the hadas is valid.
However, the Mishnah concludes: "Ve'ein me'atin beyom tov" - one may not reduce the quantity of berries on Yom Tov, since this act is considered repairing a vessel on Yom Tov, which is forbidden, and therefore it is not permitted on Yom Tov.
In summary: In this Mishnah we learned the disqualifications of the hadas - stolen and dried out (based on "lachem" and "hadar"), asherah and ir hanidachas (which stand to be burned and therefore lack the required measure), its top cut off and its leaves stripped off; and the disqualification unique to the hadas, that its berries outnumber its leaves, specifically with black or red berries. We also learned that reducing the berries renders the hadas valid, but one does not reduce them on Yom Tov because of the prohibition of repairing a vessel.