The Mitzvah
The Torah states (Vayikra 23:40(: ולקחתם לכם ביום הראשון ... וענף עץ עבת וגו' "And you shall take for yourselves on the first day... and the branch of the avos tree..." The Gemara (Sukkah 32b) explains that this refers to the hadas, because its leaves cover the wood, are braided like a chain, and the taste of its wood and fruit are the same.
We take three hadasim, together with the lulav, esrog, and aravah.
A hadas must be “lachem” (belonging to you), like the esrog. There is no issue of orlah or tevel with the hadas (the same as the lulav). A grafted hadas is invalid like a grafted esrog — but ordinarily we do not suspect grafting, since hadasim have a chazakah of not being grafted (Mishnah Berurah 648:65). One must also ensure the hadas is not dried out.
Three Leaves in Each Set of Leaves
Below we will b'ezras Hashem explain how to select a mehudar hadas.
Most invalidations — such as berries growing on the branch, small branches emerging between leaves, small leaves emerging between rows relate to growers and are not common in the marketplace. Therefore, the main effort when checking a hadas is ensuring that its leaves are tripled (meshulash) properly over a length of three tefachim.
It is clear from the Gemara (Sukkah 32b) and the Shulchan Aruch (O.C. 646:3) rules accordingly, that only a tree that is “avos" is kosher. “Avos” means that its leaves are braided like ropes, and the leaves grow together in groups of three. If it doesn't grow like this — meaning one leaf is higher or lower than the others it is called a "hadas shoteh" and is invalid even on the later days of Sukkos.
The Rema tries to justify the custom of those who use non-tripled hadasim, but the Mishnah Berurah (646:15) concludes: “One should not be lenient if it is not properly tripled. A G-d-fearing person should exert effort to find a proper “avos” branch — meaning three leaves growing at the same height in every set of three leaves.
Machlokes Rashi and Tosfos About What is Considered “Shilush”
Rashi (32b s.v. “telosa”) holds: “Shilush” means that the three leaves of each set are connected to the branch at the same height and that all three leaves come from the same root.
Tosfos writes that this is a great stringency as such a thing is very rare to find. He then brings a more lenient definition and says that all three leaves don't need to come from the same root, and it is enough that the three leaves are “close and attached to each other” and “shilush” means that the three leaves in each set of leaves come out the branch at the same height.
The Shulchan Aruch (546:3) rules like Tosfos.
Tosfos say the leaves must be "close and attached." The Rosh says, “in one circle." The Ritva says “in one row.” The Tur adds: None may be lower than the others.
The Chazon Ish's String Test (Chut Hamakif)
The Chazon Ish famously gave a geder [definition] (quoted by Rav Chaim Greineman zt”l, Chiddushim U’Biurim Sukkah 5):
To be meshulash, the leaves do not need to be perfectly aligned at the exact same level - to find such a thing is extremely rare. Rather, each leaf of a hadas is connected to the branch by a stem with a “root” that is thicker than the rest of the stem and takes up some space on the branch. If the groups of leaves are aligned to the point that a string can be wrapped around the branch's circumference at the leaves' point of connection and touch each leaf stem's root it is okay. Even if the string would go over the upper end of one root and the lower end of another, the hadas is considered meshulash and is lechatchilah. The Kehillos Yaakov (Sukkah, Likutim) brings proof to this from the Yerushalmi.
Rav Dovid Soloveitchik, quoting the Brisker Rav zt”l in the name of Rav Chaim Brisker zt"l; Rav Nissim Karelitz zt"l; and Rav Chaim Kanievsky zt"l in the name of the Chazon Ish (cited in Arbas HaMinim L’Mehadrin, pg. 182 see picture attached on the right) all practically ruled that: If a string would go over all the roots the hadas is lechatchilah.
Small Protrusion
On many hadasim, the leaf stems come out of small protrusions on the branch. Some poskim hold these protrusions are part of the root of the leaf stem, and if they are aligned along the circumference, the group of leaves is considered meshulash (Rav Chaim Kanievsky zt”l, Kashrus Arbas HaMinim, pg. 88).
Others say the protrusions can be viewed as part of the roots with respect to the leaves' alignment only if all the leaves look like they are in one group (Chut Shoni, Perek 15, s.k. 2).
Unclear
Some poskim are machmir if the “string test" for the alignment of the leaves around the circumference would be borderline or come close (Brisker Rav), but most poskim say as long as the leaves look like they are part of one group, it is fine lechatchilah (R' Nissim zt"l and R' Chaim Kanievsky in the name of the Chazon Ish).
"Appears Meshulash” vs. “Actually Meshulash"
Some say it is not enough that it appears to be meshulash and the hadas must actually have the leaves all at the same height. Others say appearance is enough (Madrich Maasi Lebedikas Arbas HaMinim, pg. 27) and they hold that if it is held a measuring distance of around 35 cm and it looks meshulash it is good enough.
In Halichos Sholmah (Sukkah, Perek 10, Orchos Halachah 43) they bring from R' Shlomah Zalman Auerbach zt”l that the main requirement is that it appears meshulash in its growth pattern and he did not check it with a string.
Although, he did not rule like this for others, and for most people he would tell them to check it with a string.
The Required Length of Meshulash
Length of the Hadas:
The Shulchan Aruch (O.C. 650:1) rules that lechatchilah a hadas should be 12 thumb-widths (3 tefachim, as each tefach is four thumb-widths). According to Rav Chaim Naeh it comes out to 24 cm and according to the Chazon Ish it comes out to 30 cm.
Bedieved 10 thumb-widths is enough, which according to Rav Chaim Naeh comes out to 20 cm and according to the Chazon Ish it comes out to 24 cm.
Where to Measure:
From the lowest place where the leaves come out as a set of three until the top of the branch. The upper leaves that protrude above the branch are not included (Mishnah Berurah 650:1).
Mehudar:
It is clear from the Shulchan Aruch (646:5) that for mitzvah min haʼmuvchar the entire length should be meshulash. According to Rav Chaim Naeh 24 cm and according to the Chazon Ish 30 cm.
Kosher:
To be kosher for a berachah the hadas doesn't need to be fully meshulash and it is enough if the majority is meshulash.
The Bikurei Yaakov and Birkei Yosef (quoted in Kaf HaChaim 646:38) learn that anything more than half is kosher. Meaning: According to Rav Chaim Naeh 13 cm and according to the Chazon Ish 16 cm.
The Mishnah Berurah (646:18) writes that the hadas must be “avos” for 7 of the 12 thumb-widths.
The Biur Halachah (646 d.h. leikuva) writes “close to two tefachim.”
The Kaf HaChaim brings that some say it must be a majority that is visible to the eye.
The Pri Megodim (M.Z. 646 s.k. 9, cited practically in Orchos Rabbeinu pg. 250) writes “two tefachim and bit".
The Bach (cited in Biur Halachah 646) writes that if the hadas is very long i.e. 6 tefachim it is still kosher even if it is only meshulash the amount of what is needed for a three tefachim long hadas.
Various Other Halachos Regarding Hadasim
Severed Upper Leaves:
If some of the upper leaves of a hadas got severed, it is still kosher (Mishnah Berurah s.k. 35) since the pasuk calls a hadas an “anaf eitz avos” referring to the wooden stem, not the leaves.
Severed Stem:
If the stem got severed, some poskim hold it is still kosher (first opinion in Shulchan Aruch sif 10). Such a flaw invalidates a lulav, esrog, or arovoh since it is visible; however, a hadas's leaves cover its top and conceal the fact that the top of the wooden stem was severed (Mishnah Berurah s.k. 29).
Others say it is pasul since it is not “hadar” (second opinion in Shulchan Aruch). The Rema concludes: If possible, it is best to be machmir and choose another one.
Severed Stem and Upper Leaves:
If the top of the stem was severed and the upper leaves were either also severed or fell off, revealing the flaw in the stem, some say even the poskim who hold a hadas with a severed top is kosher would hold this hadas is pasul since the flaw is visible (Pri Megodim, M.Z. s.k. 12; Bikurei Yaakov s.k. 22). Even if just one leaf got severed, they hold it is pasul since the flaw is visible from one angle (Shaar HaTziyun s.k. 32). The way to fix this would be to snip the branch by the next group of leaves [assuming the hadas would still have the minimum length]. That way, the top of the branch is covered by leaves. However, this cannot be done on Yom Tov due to the issur of mesakein (Bikurei Yaakov).
Others say that according to the poskim who hold a hadas with a severed top is kosher, it is kosher even if the top of the stem and upper leaves were severed. When they said it is kosher because the flaw is concealed, they meant that to be hadar, hadasim just need to be meshulash; whether or not the top is intact does not affect the beauty (Chazon Ish, 146:30).
Scattered Meshulash:
The three meshulash tefachim do not need to be consecutive. As long as there is a total of three meshulash tefachim, the hadas is kosher lechatchilah even if they are spread out through the branch. The same is true for a rov of three tefachim meshulash: even if the meshulash leaves are spread out, they can be counted for the rov meshulash as long as they are also the majority of the leaves on the branch. (This is the final ruling of R' Chaim Blier in Chukei Chaim, however, the Biur Halachah 646 d.h. uleikuva is in doubt about this and many poskim say to be stringent, see for example Shu”t Shevet HaLevi 7:82)
In Orchos Rabbeinu (pg. 249) they bring that even the Pri Megodim who leans towards be stringent with this shailah, agrees that if the majority of meshulash is within the same three tefochim it is kosher. They add: During Chol HaMoed, leaves often fall, and we rely on the fact that most of the hadas remains “avos.”
Fallen leaves:
It is clear from the Mishnah Berurah (646:18) that if the hadas was originally meshulash, and some leaves fell, and most of the hadas remains meshulash – it is kosher. If most leaves fell off then it is invalid.
The Biur Halachah discusses the details of leaves falling off at length.
The Shaar HaTziyun (646:19) quotes the Geonim who hold that if even one leaf fell from the entire length of the hadas it is invalid.
The Chut Shani (646 ois 3) writes: Practically, if one leaf fell, it is still kosher lechatchilah - since during Yom Tov leaves naturally fall, and it is hard to find a hadas with zero fallen leaves. But it loses some hiddur, so meticulous people look to find one without any fallen leaves.
The Bikurei Yaakov (646:4) writes: If the minority of a leaf is cut it is kosher. If the majority is cut the leaf is considered as if it is not there.
Leaves of One Set Don't Reach the Leaves of the Set Above:
If lower leaves do not reach the stems of upper leaves because the sets of leaves are spaced apart, according to the Bikurei Yaakov (646:11) it is kosher, however, according to the Mor U’Ketziah it is invalid. The sefer Chaim U’Berachah (ois 59) writes: It is mehudar to have them close and covering the entire wood, but if no other hadas is available it is kosher.
Leaves Don't Lie on the Branch:
If the leaf reaches the leaf above but does not lie on the branch, but rather leans sideways, the Bikurei Yaakov (646:11) and Chazon Ish (15:1) rule it is kosher. However, the Reshash (Sukkah 32b) holds it is invalid and he questions the widespread minhag of people who are lenient. He leaves off tzorich iyun.
Leaves Leaning Downward:
The Chazon Ish (146:32,35) discusses this and says it may be invalid for several reasons.
Summary of Dinim that Come Out:
Avos: “Anaf eitz avos” Chazal interpret to mean a hadas whose leaves cover its stem. A hadas must be “avos”, meaning made up of leaves which grow in sets of three. If it doesn't have this it is a hadas shoteh and is invalid. It must be “lachem”, not grafted and not dried out.
One Root: According to Rashi the three leaves must come from one root. Tosfos argues and says that it is enough that they are close by even if they come from three different roots. We pasken like Tosfos. To determine if the leaves are meshulash one may use the string test and if it goes through all three leaves near to where they connect to the branch it is okay.
Meshulash: Ideally, the hadas must be meshulash with its leaves growing in sets of three along the full halachic length of three tefachim: according to R' Chaim Naeh, approximately 24 cm, and according to the Chazon Ish, approximately 30 cm.
At the very least, the majority of three tefachim must be meshulash: according to R' Chaim Naeh, about 20 cm, and according to the Chazon Ish, about 24 cm.
Fallen Leaves:
If the hadas was originally properly meshulash and some leaves later fell off as long as the majority of the hadas remains properly meshulash, it is kosher.
If most of the leaves have fallen off, it is invalid.
Ideally, one should seek a hadas from which not a single leaf has fallen, because according to the opinion of the Geonim, it is invalid even if one leaf is missing.
Searching for the Perfect Hadasim
Rabbi Eliezer Yudakovski shlita relates the following: In my younger years, I once went out to look for hadassim for my lulav. In those days, finding truly beautiful hadasim was one of the hardest tasks when it came to Arba Minim. They weren't sorted and packaged as they are today. The branches arrived in buckets, and one had to examine them carefully — checking each hadas one by one, measuring the distances between the leaves, and so on.
Of course, I wasn't the only one in the Arba Minim market. Many Jews came to buy hadassim, and it was far from simple to find beautiful ones among all those branches that others had already gone through, selecting the best.
So, I decided to travel farther. I went to Petach Tikva, thinking that there weren't as many bnei Torah there as in Bnei Brak, and therefore I might find hadassim more easily.
I searched the entire day and finally found three branches of hadas: two were truly beautiful, and the third was very fine but had a tiny imperfection.
I brought the three hadassim to Maran Rav Aharon Leib Shteinman, who in those years still received people with questions about the Arba Minim, until his eyesight weakened somewhat and he stopped answering such questions.
Rav Shteinman examined the hadassim and said to me: “Two of these are excellent, but the third could be better... it would be worthwhile to buy another one!"
I said to Maran, "But I already spent an entire day searching for these hadassim!"
He replied: "Nu, what's the problem? Then invest one more day and you'll have three hadassim of the highest beauty!”
The next day, I traveled again to Petach Tikva, and after several hours of effort, I succeeded in finding the most beautiful hadas of all.