The Mitzva of Hadas: Myrtle or Leafy Branch?

  • Harav Mosheh Lichtenstein


And you shall take for yourselves on the first day, the fruit of goodly trees (peri etz hadar), the branches of palm trees (kapot temarim), and the boughs of leafy trees (anaf etz avot), and the willows of the brook (arvei nachal), and you shall rejoice before the Lord, your God, for seven days. (Vayikra 23:40)
            Every schoolchild knows that this verse refers to the etrog, lulav (palm), hadas (myrtle) and arava (willow) respectively. However, it is interesting to note that the Torah refers to the four species in dissimilar fashions. While the lulav and the arava are mentioned by name, and their species are recalled explicitly in the Torah, the etrog and the hadas are not mentioned by name; the Torah only provides us with their descriptions, from which we must deduce what kind of plant to take. Why did the Torah distinguish between the four species, choosing not to treat them all equally?    
            This question obtains especially to the hadas, the only one of the three types of plants[1] that is not explicitly named. The three types of plants are bound together and form their own cohesive grouping, yet the hadas stands out because it goes unnamed. Furthermore, according to the Ramban (p. 31),[2] the phrase “fruit of hadar trees” is actually the Hebrew name for the fruit to be taken, the word etrog being the Aramaic translation of the Hebrew word hadar. Thus, our difficulty intensifies, for according to the Ramban, the hadas is the only one of the four species that is not explicitly named. If one should argue that “boughs of leafy trees” (anaf etz avot[3]) also names the type of plant and does not just describe it, the answer is implicit in the question, for the word hadas appears in several places in the biblical text and therefore does not derive exclusively from the language of the Sages (as etrog does, according to the Ramban).[4]        
The Ramban wrote (ibid.): “Hadar mentioned in the Torah in connection with etrog is similar to avot mentioned in connection with hadas and kapot mentioned in connection with lulav – all of them are denoted by the names of their species.” That is to say, the Ramban disagrees with our above assumption; in his opinion, the Torah did mention the hadas species. However, the fact that this very issue – whether the Torah explicitly named the hadas species or whether it just described its characteristics – is under dispute provides a key to understanding the sugyot dealing with this topic.  In the following discussion, we will attempt to determine the essential nature of the mitzva of the hadas.[5]  
We learn in the Mishna:
A hadas that was obtained through robbery or that has dried out is unfit for ritual use. [One] stemming from a tree dedicated to idolatry (asherah) or coming from a condemned city is unfit for ritual use. If its tip has been shorn (or broken) off, its leaves have become separated, or its berries are more numerous than its leaves, it is unfit for ritual use, but if one reduced their number, it is valid for ritual use. (3:3)
In and of itself, the mishna does not present any fresh insights; it integrates seamlessly into the sequence of four mishnayot opening the third chapter of Sukka. It reiterates the same halakhic details regarding each of the four species: stolen, dried out, etc.[6] However, the Mishna, in the continuation of this chapter, creates a difficult dilemma:
R. Yishmael says: Three hadasim and two aravot, one lulav and one etrog, even if two have their tips broken off, and one does not. R. Tarfon says: Even if all three have their tips broken off. R. Akiva says: Just as we require one lulav and one etrog, so, too, we require one hadas and one arava. (3:4)
Aside from the contradiction between this mishna and the preceding one regarding ketima (the law of a hadas whose tip was broken or shorn off) – a contradiction which greatly occupied the foremost Rishonim, as will become clear later – there is an immense difficulty with the mishna itself. Whether we adopt the approach of the Rif, the Rambam, and the Ramban that the two mishnayot are in dispute regarding the law of ketima, or whether we adopt the approach of the Ra’avad (p. 14) and the Ba’al Ha-ma’or[7] that there are two types of broken tips, it is difficult to explain why this dispute is not cited in the previous mishna. After all, the former mishna deals with those elements which invalidate a hadas from ritual use, and explicitly discusses the issue of a hadas whose tip was broken. If R. Tarfon and R. Yishmael really do dispute the ruling of the previous mishna (or provide an additional distinction regarding the laws of the hadas whose tip is broken off), the most logical place to cite their approaches would have been in the previous mishna, alongside the anonymous opinion stated by the tanna kamma.
            Not only does it make no sense to defer the discussion to elsewhere, but the place chosen to resume it is inherently unsuitable: the dispute concerning ketima brutally disrupts the flow of the mishna (3:4) where it is located. Thus, following the discussion in the opening mishnayot of chapter three of the factors that invalidate the four species, mishna 4 enumerates the number of each species necessary and presents a Tannaitic dispute on this matter. The discussion concerning hadasim with their tips broken off finds it way into the midst of the mishna’s dispute between R. Tarfon, R. Yishmael and R. Akiva regarding the number of each species necessary, momentarily stopping the dispute in its tracks.  If we were to divide the two mishnayot into their component parts, and asked an average student in the beit midrash to reassemble the mishnayot, he would certainly join the two segments concerning ketima together, and then he would conjoin the various stances concerning the number of each species required, thereby forming one unbroken sequence.
            If this thought experiment does not prove my point, no lesser authority than the Rambam adopted this very approach. He recorded the law concerning the required number of each species in one chapter (7:7), but held off recording the law concerning ketima until the next chapter (8:5) – where he discusses those elements which invalidate the species from ritual use. And this, even though he rules in accord with R. Tarfon in both chapters, and R. Tarfon’s two rulings are stated in tandem in the mishna.
            Two problems with the organization of the Mishna arise from the preceding discussion. A. Why was the ketima dispute not cited in what seems to be its appropriate place in the chapter? B. Why does this segment separate between R. Yishmael and R. Tarfon, the Tannaim who are on the same side of the dispute, in the mishna’s account of their disagreement with R. Akiva?
            It seems obvious that one question answers the other, and that there is a strong, deep-seated connection between the two disputes. Indeed, no mishna can ever be stopped in its tracks. Rather, this mishna embodies the principles of sequential flow and continuity, and abhors discontinuity and division. The very permission to use a hadas whose tip was shorn off is dependent upon the number of hadasim necessary, and it bears witness to the essential nature of the hadas, according to those who maintain that three hadasim are required. Therefore, in organizing the mishnayot in this fashion, Rabbi Yehuda Ha-nasi did not stop the sequential flow in its tracks, for the two disputes are intrinsically connected.
Examining these two questions offers us the opportunity to determine whether the phrase anaf etz avot, used by the Torah, names the type of plant, as the Ramban contends, or simply describes it. As noted above, a simple reading of the verse indicates that this phrase simply describes the required plant, rather than naming a particular type of plant. Taking this insight to its logical conclusion, we realize that in principle the Torah does not require that we take a hadas; any plant embodying the necessary prerequisites – a leafy foliage with many densely packed leaves – could be used to perform the commandment.
This insight also seems to be a given in the sugya (32b) that examined whether other trees were fit to be defined as anaf etz avot. Ultimately, the other options were rejected only because they did not fulfill all of the prerequisites:
Our Rabbis learned in a Baraita: Anaf etz avot – [a plant] whose boughs cover its wood. And which is this? Let us say the hadas. And might not the olive tree be meant? We require the precondition of avot, and the olive tree lacks this. And might not the plane-tree [others translate, chestnut] be meant? We require that its ‘boughs cover its wood,’ and this prerequisite is lacking. And might not the oleander (hirduf) be meant? Abbaye said: ‘Its ways are the ways of pleasantness,’ and this characteristic is missing. Rava said, [We learn to reject the oleander] from this verse: ‘And you shall love truth and peace.’
Presumably, the Ramban would argue that these signs were provided to resolve any doubt, and definitively establish that the hadas was the plant specified by the Torah. However, the sugya clearly implies, as the Tosafot note (33a, s.v. ve-eima), that other leafy plants might be valid for performing the mitzva. Consider the following. The Gemara investigated the possibility of using alternate, or additional, types of plants only in the cases of the etrog and the hadas. With regard to the lulav and arava, the notion of using any other type of plant was never even raised. This difference does not result from the fact that the names lulav and arava were more commonly used, while the appellations employed by the Torah for etrog and hadas were unknown and therefore demanded in-depth investigation. Rather, the reason for this is obvious: the Torah provided a description of the types of plants fit to be used to fulfill the roles eventually played by the hadas and the etrog; any plant matching these descriptions could have been used to perform the commandment. This statement bears particularly upon the case of the hadas, which the Torah consciously chose to describe, rather than to name explicitly.
The Tannaitic dispute concerning the number of hadasim required and other disputes concerning the halakhic minutiae related to the hadas, seem to stem from the question of whether anaf etz avot denotes a particular plant or whether it describes a type of plant. If the phrase anaf etz avot is merely descriptive, then the Torah did not designate the hadas plant specifically. Any plant possessing avot, expressing the abundance found in nature, would have fit the bill. Thus, we need not concern ourselves with the symbolism, or any other element, particular to a specific plant; the Torah wishes us to focus upon the cornucopia found in nature, expressed by the dense foliage of the hadas leaves. Therefore, the Gemara investigated whether other plants or trees, like the olive tree or the plane tree, could also be used to perform this mitzva.
However, the sugya (33a) concerning asa mitzra’ah (literally, an Egyptian hadas, a hadas possessing a cluster of seven leaves growing from one point in the stalk) seems to contradict this contention:
Abbaye said: From this we may infer that the Egyptian hadas (some translate, ‘boundary hadas’) may take its place in the hoshana bundle. This is obvious! You might say that since its name is modified (by the word, Egyptian), it becomes invalid; we learn that this is not so. And why not say that this is true? The Merciful One prescribed an etz avot, no matter what the circumstances [it grows in].
While the asa mitzra’ah’s species name is modified, and therefore it cannot be classified as belonging to the species of normal hadas, it nevertheless may be used for the performance of the mitzvot because it possesses the characteristic of avot. This is the point made by the Gemara when it asks “And why not say that this is also true?” Perhaps the Egyptian hadas really is a different species and should be invalid. The Gemara responds that the Torah does not require a plant from the hadas species; rather, it requires the prerequisite of avot: “The Merciful One prescribed an etz avot, no matter the circumstances [it grow in].” Thus, our query is presented as both the hava amina (original assumption) and conclusion in this sugya dealing with the status of the Egyptian hadas.    
The Ramban will, of course, explain that the very point of this sugya is to teach us that the Egyptian hadas is part of the hadas family, irrespective of its additional title. However, it is difficult to understand how this can be learned from the phrase etz avot. See the Tosafot ad locum (s.v. ve-eima), which finds our reading of the sugya so obvious that it has difficulty comprehending the Gemara’s question in the first place. However, clearly the issue is not that clear-cut, and, therefore, the Gemara entertained a hava amina that a particular species had to be taken to perform the mitzva of hadas.
The Gemara presents another sugya (32b):
Our Rabbis learned in a Baraita: Plaited like a braid, and similar to an interlocking chain – this is a hadas. Rabbi Eliezer ben Yaakov says: ‘Anaf etz avot’ – a tree whose wood and fruit taste the same; you must say, this is a hadas.
Thus, the tanna kamma perceives the essential nature of the hadas to be the way its leaves are arranged, while Rabbi Eliezer ben Yaakov focuses upon a different trait. Our discussion regarding the significance of the “avot” characteristic fits in well with the tanna kamma’s approach, but not with Rabbi Eliezer ben Yaakov’s.
Having adduced this dispute, we can now argue that it is the root cause of the Tannaitic dispute concerning what number from each species must be taken. If the hadas represents the abundance and life force of the growing world, then, as R. Yishmael and R. Tarfon contend, this should not only be expressed by the plant’s form, but also by its number: three hadasim must be taken. However, if we are intent upon taking this plant, in and of itself, then only one hadas is necessary. Just as we take one lulav and one etrog, in R. Akiva’s opinion, we need take only one hadas.
Given this insight, it is not surprising to discover that the Ramban, who is the primary advocate for anaf etz avot naming the species, writes the following:
In keeping with the plain meaning of Scripture, the verse is stating that we should take for ourselves a pri etz hadar, kapot temarim, one bough of etz avot, and one bough of arvei nachal... for the halakha follows the opinion of Rabbi Akiva that “Just as only one lulav is needed and only one etrog, so too only one hadas and only one arava.” (Vayikra 23:40)    
Thus, it is clear to us that the Ramban privileges the hadas species because of its form and not because of the abundance it alludes to. Therefore, the Ramban adopts the ruling of R. Akiva, that even one hadas is enough.
The Tosafot commented upon and questioned the following baraita cited in the Gemara:
We have learned in a Baraita: Rabbi Yishmael states: Peri etz hadar – one, kapot temarim – one, anaf etz avot – three, arvei nachal – two. (34b)
The Tosafot wrote:
Rashi explained that anaf indicates one, etz indicates one, avot indicates one. And this is surprising, for above (32b) these words were interpreted in the following manner: anaf – a tree whose boughs cover its wood; and likewise, etz avot – plaited like a braid. (s.v. anaf)
The Tosafot failed to find a satisfactory answer to their query regarding how both the required number of hadasim needed and the form of the species could be homiletically deduced from the same verse. However, from our perspective, the answer to this question seems obvious. We do not deduce the need for many hadasim from a homiletical reading of the verse; rather, we infer it from the biblical text itself. The explicit demand for a plant with many boughs and dense foliage inherently demands the use of many such plants, for both type and number manifest the notion of avot and the abundance found in the natural world. Since the number of hadasim required, according to our approach, is not homiletically deduced from a superfluity in the verse, the verse can be used for other homiletical purposes.
     Thus, R. Yishmael and R. Tarfon dispute with R. Akiva regarding the essential nature of the commandment to take the hadas, not just regarding the number of hadasim to be taken. The reason why the issue of ketima was discussed in the mishna alongside the issue of how many hadasim were to be taken is because both disputes seem to derive from the same dilemma. If we are commanded to take the specific species called hadas, then, like any one of the other three species, a hadas whose tip has been shorn off is invalidated for use, since the essential beauty of all four species resides in their tips and damage done to them invalidates them. Following this logic, the first mishna invalidated a hadas whose tip had been cut off, making no distinction between the hadas and the other three species. However, in the following mishna, where the Tannaim dispute the number of required hadasim, R. Yishmael and R. Tarfon introduced a new understanding of the commandment to take the hadas. In their opinion, the commandment does not pertain specifically to the hadas species; rather, the focus is upon taking a plant symbolizing the abundance of the natural world reflected by the form of the hadas and the number of hadasim taken. Thus, a hadas whose tip has been cut off can still be valid, for it still represents the profusion and abundance of the growing world, and its lack of the “beauty” required by all the other species is irrelevant. Therefore, R. Tarfon and R. Yishmael, who require three hadasim to reflect the profusion and abundance, validate hadasim whose tips have been cut off, while R. Akiva, who stipulates the need for this particular species, only requires one hadas, but invalidates a hadas whose tip has been clipped off.
In conclusion, R. Tarfon and R. Yishmael dispute the fundamental basis of the first mishna, and the two disputes, are, in fact, one. Therefore, the disputes are presented in tandem: the second mishna dealing with the number of required hadasim is not abruptly disrupted by the introduction of ketima because the halakhic stances taken regarding these two matters reinforce and validate each other. Therefore, it was most fitting that they be cited in tandem, so that ketima functions as another practical manifestation of the fundamental dispute, rather than being addressed as a separate matter in the previous mishna.
Strikingly, R. Yishmael’s ruling that at least one of the three hadasim must be whole is problematic. For no matter what explanation you give, you wind up in contradiction: if a hadas whose tip has been cut off is valid, then even if all three have their tips cut off they should be valid, and if a hadas whose tip is cut off is invalid, then how can a bunch of three hadasim, where even only one has had its tip cut off, be valid? The Gemara already raised this question and was forced to conclude the R. Yishmael retracted this ruling:
And concerning the opinion of R. Yishmael, whatever explanation you wish to give is problematic: If R. Yishmael requires whole hadasim, he should require that all three be whole. And if he does not require whole hadasim, he should not require even one. Bira’ah said in the name of R. Ami: R. Yishmael retracted his original opinion. (34b)
However, the Jerusalem Talmud (3:4) maintains that R. Yishmael did not disavow his approach in the mishna. Whether or not R. Yishmael disavowed this approach, the logic of either his original hava amina in the Babylonian Talmud or of his final ruling in the Jerusalem Talmud requires elucidation.
In light of our insight, R. Yishmael’s approach is perfectly clear. In his opinion, in taking the hadas one performs two mitzva acts: taking the particular species itself, and taking a symbol of the abundance implied by the term avot. On the one hand, the principle of abundance and profusion must be expressed, so three hadasim must be taken; however, since the symbolic value is paramount, all three can have their tips clipped off. On the other hand, the hadas qua hadas must be taken, so at least one whole hadas (but not necessarily any more than one) must be taken. Thus, according to R. Yishmael only one whole hadas must be taken to perform taking the hadas qua hadas, but two more hadasim (not necessarily whole ones) are needed to complete the taking of avot. In contrast, R. Tarfon (and according to R. Ami, R. Yishmael after he disavows his original stance) believes that in taking the hadas, only one act is accomplished, the symbolic taking of avot, so not even one hadas has to be whole.
Notably, our explanation of the dispute concerning ketima was developed in keeping with the approach of the Rif and those – the Rambam and the Ramban - who contend like him that both mishnayot deal with the same case. They force us to conclude that the Tannaim must disagree regarding the halakhic status of the hadas itself, whose tip has been shorn off. However, according to the Ra’avad and the Ba‘al Ha-Ma’or, “Any Torah scholar with eyes in his head will come to realize that the [case of] hadasim with their tips cut off cited by R. Tarfon and R. Yishmael is not the same [case] which we learned at the beginning of the mishna.”[8] According to them, the hadas katum, whose tip has been cut off, that is ruled valid in the second mishna, is not the same as the one whose tip was cut off (niktam rosho) and invalidated in the earlier mishna. However, our approach makes an even greater impact in the context of their understanding of the mishnayot.
The Ra’avad contends that the second mishna addresses the question of whether the entire plant has to be whole – “not cut off from the trunk; rather, the entire trunk is whole with its foliage” - or whether even a bough that has been clipped off from the trunk can be ruled valid. We must explain why a complete plant would be required and not just a bough. Furthermore, what is R. Tarfon teaching us by ruling that a clipped hadas is valid, and what prompts R. Yishmael (before he disavows his approach, according to the Babylonian Talmud) to require a complete plant (trunk and all) to fulfill the requirement of each anaf, laws specific to the hadas alone?
The Ramban already expressed great surprise at this approach in the following blistering attack: “This interpretation is far from reason, for if it were true, why didn’t any Torah scholar invalidate hadasim whose tips were clipped or that were split open far more frequently than any of the other species? In fact, the opposite occurred; everyone agrees that the hadas is valid, for the term anaf is used to name it.”[9] This question, indeed, cries out for an answer.
The approach of the Ra’avad and the Ba‘al Ha-Maor seems to be fairly easily explained by applying the approach we have taken. Since performing the commandment of taking the hadas requires taking a plant that is avot (not just a hadas), one might think that we are required to take a whole plant, trunk and all, not just an individual bough pruned off the plant. Therefore, R. Tarfon made sure to inform us that even though he maintains that taking a hadas entails the symbolism of taking a plant that is avot, this does not necessitate taking the entire trunk or a branch that grew by itself in the ground; a bough clipped off the trunk is sufficient. In this respect, the hadas is intrinsically different than the lulav and arava, so the Ramban’s question automatically becomes null and void. The Ramban himself, however, cannot offer this answer because he maintains that the phrase anaf etz avot does not describe the plant, but rather names it. So our approach offers him no intrinsic difference between the hadas and the other three species, and therefore, from his perspective, his question still stands.
If our argument is valid, namely, that the number of hadasim required testifies to a celebration of the profusion of the plant world, then we can easily explain the Rambam’s well-known stance regarding the number of each species to be taken and adding to them:
How many of each species is taken? One lulav, one etrog, and two twigs of arava, and three twigs of hadas. And if he wishes to add more hadasim, in order to create a large bunch, he is permitted to do so, and this is considered noyei mitzva (beautifying or ornamenting the commandment). But one may neither increase nor decrease the number of the other species taken. If one has increased or decreased [the number of the other species], he has (not) invalidated. (7:7)
The Rambam is clearly differentiating between increasing the numbers of hadas and arava twigs, in contrast to many other Rishonim who permit an increase in the number of both species. The commentaries have already questioned why the Rambam differentiates between the two, given that the mishna did not differentiate between them when stating the number of each to be taken. However, in light of our approach, the reason is clear. In order to perform the commandment of taking the arava, one must take a specific species. The requirement of taking two aravot is deduced from the plural form used by the verse; that is to say, the number of arava twigs to be taken is specially enumerated, and therefore neither more nor less may be taken than that set down by the verse. In contrast, to perform the commandment of taking the hadas, one need not take a specific species and the command to take three is not homiletically deduced from the verse. The emphasis on the profusion of growing things applies to both the form of the hadas leaves and the number; therefore, anyone who wishes to increase the number is to be praised.
For this very reason, many Rishonim permitted the addition of hadasim shotim (usually translated as wild myrtle), certain that there was no violation of bal tosif (the biblical prohibition to add to the mitzvot) with the addition of a fifth species. Given that the Torah did not prescribe a specific species be taken, but rather emphasized the profusion of growing things, the wild hadas also helps fulfill this goal (as will be explained at length later).
The Maggid Mishneh (ibid., s.v. ve-im) differentiated between the hadas and the arava regarding additional twigs because the hadas’s function is ornamental, while the arava’s is not.[10] This explanation makes sense if we accept the premise that the specific species of arava must be taken, while the hadas is taken because of the beauty inhering in profusion itself. If the Torah had demanded the specific species of hadas, one bough could have been taken to fulfill the commandment and any additions would be forbidden because of bal tosif.
While this approach explains the Rambam’s ruling clearly, the Rambam may not be able to profit from it. For the Rambam’s language in 7:2, although inconclusive, seems to lean towards the stance that anaf etz avot denotes the hadas’s species, rather than simply describing it. The Rambam’s ruling regarding a hadas whose leaves had shed (to be discussed later) also seems to embrace the latter approach.  However, the Rambam ruled in accord with R. Tarfon, both regarding the number of hadasim to be taken (7:7) and the laws pertaining to ketima (8:5). Thus, we can only claim that our approach enables this particular halakha to be explained, even though we cannot use this knowledge to prove the Rambam’s over-arching conception of hadas.
We may now return to our opening question: why did Scriptures describe the hadas, rather than denoting it by the name of its species? According to R. Tarfon and R. Yishmael, who regard “anaf etz avot” as a description and not a name, the Torah does this in order to establish that the species be taken from a tree possessing the characteristic of avot. The Torah has not employed a backhanded way to enable us to identify the hadas; rather, it has set down the essential component of the mitzva.
In light of this realization, we should discuss the dispute among the Rishonim concerning the halakhic status of a hadas whose leaves have shed. If the Torah commands us to take the species known as hadas, then the probability is greater that a hadas that lost its leaves be declared valid, since, even though it does not look much like a hadas, it still belongs to that species. However, if the Torah requires us to take a plant possessing the characteristic of avot, now that the leaves have fallen off, the twig does not possess this prerequisite and it is invalid for ritual use. 
The Rambam (8:5) permits the use of a hadas “most of whose leaves have shed, if three leaves remain in one bud (kan),” because it is of the hadas species. The Ra’avad wrote concerning this matter: “We require the characteristic of avot to be present over a majority of the required length.” According to the Ra’avad, even if the species taken is the correct one, one may fail to perform the mitzva of taking avot.[11]
The Ritva (32b, s.v. tanu rabbanan nashru) cited the opinion that a hadas twig is invalid if even one leaf shed, for there is a requirement that it be entirely avot. He also cited the Ra’ah’s reaction to this opinion.  He believes that there are two aspects to the requirement of avot: defining the particular species and appearing as avot. From the perspective of defining the particular species, the entire required length must be avot. If the species lacks this characteristic, it is not the species mandated by the Torah. From the perspective of appearance, if a twig from the correct species shed its leaves, while there is still a requirement that the twig be avot, it is sufficient if a majority of the twig possesses this characteristic.
Having reached this point, we should now examine the sugya of the hadas shoteh (wild myrtle). The Amoraim do not agree whether or not to disqualify the hadas shoteh because it fails to produce three leaves from one root, and it is not even clear whether the Gemara finally decides to disqualify it or not.[12] After taking the position that the Gemara disqualifies the hadas shoteh, the Rishonim argued whether shoteh is a disqualifying factor, in and of itself, preventing the hadas shoteh’s approval, or whether a hadas shoteh is invalid simply because it is not a member of the hadas species. There are three practical ramifications to whichever side of this argument is adopted:
1.Is the hadas shoteh invalid for the entire seven-day holiday, or is it only invalid for the first day?
2.In a case of pressing need, can it be ruled valid?
3.The mandatory length of the hadas: Does the entire mandatory length need to have three leaves consistently emerging together from the same level (fulfilling the prescription of meshulash) or is it enough for the leaves on the majority of the length to do so?
Clearly, if the hadas shoteh is not a member of the hadas species, then it is disqualified for the entire holiday and even in times of pressing need. And if the hadas shoteh is valid after the first day of the holiday or in times of pressing need, then clearly it is a member of the hadas species, possessing a particular disqualifying factor. The Ra’avad declared:
That which does not possess the characteristic of avot is a different species. And the condition of avot must be fulfilled every day, for it does not derive from the requirement of hadar (beautifying the four species), but rather it is intrinsic to the mitzva itself. (p.13)
The Ramban (p.34) agreed with this and even compared the relationship between the hadas shoteh and the hadas with the relationship between the tzaftzefa (according to some, the white willow) and the arava.[13] The Maggid Mishneh (7:2) raised this issue with respect to how much of the hadas meshulash must be avot, writing: “I declare that all of them should be, for every part which does not possess the characteristic of avot is like a different species, and therefore the hadas will not be long enough.” However, the halakhic ruling of the Rema (Orach Chaim 646:3) that in cases of pressing need one can perform the commandment with a hadas shoteh is well known. We are forced to acknowledge that the Rema must have disagreed with the Rishonim just mentioned.
We can base a response to these questions upon our approach above. If the Torah wished avot to be a sign, identifying the hadas species, then a hadas shoteh is invalid. One might even tend to think, like the Rishonim, that the Torah classifies the hadas shoteh as belonging to a different species. However, if the Torah does not demand a particular species, but rather emphasizes taking a tree with the characteristic of avot, then clearly the hadas shoteh is not invalid; it merely fails to display the characteristic of avot. Therefore, perhaps a hadas shoteh can be used, for in principle it possesses the characteristic of avot. Therefore, certain stances in the Gemara (32b) completely validate the hadas shoteh, for in their opinion, the prerequisite of avot has been fulfilled. In any event, in cases of pressing need or on the second day of the holiday, it seems most likely that one can perform the mitzva using the lesser quantity of avot found in the hadas shoteh, as prescribed by the Rema.
In light of this, we can provide a rationale for the Rema’s additional claim justifying the rampant use of the hadas shoteh in the northern lands:           
There is one who writes that our hadasim are not classified as hadas shoteh since they possess [a configuration of] two [leaves] above [another] two [leaves], and [so] they are unlike the hadas shoteh mentioned in the Gemara, and, therefore, they were accustomed to ruling leniently.  
The Acharonim have already expressed their astonishment at the logic underlying the Rema’s apologetics. As the Mishna Berura writes ad locum:
See the Biur Ha-Gra and the other Acharonim who all had great misgivings regarding this custom, for [the Sages] had no foundation for [permitting] two [leaves] upon one or two [leaves] upon two, and the Rema was pressed to find a justification for the custom. And, therefore, one who is careful to perform the words of God should trouble himself to find legally valid avot, that is, [hadasim] where there are three leaves on the same level coming out of every single bud. (s.k. 15)
In the Biur Halakha, he added:   
See the Bikurei Yaakov, who expressed amazement at this, for in any case it is not within the parameters of avot as described by the Torah, for this specifically requires three leaves; and see therein where he proved that even those who are lenient in cases of pressing need only do so in a case of two and one; however, we have nothing to rely upon to permit two and two … (s.v. ho’il)
Apparently, those who critique the Rema’s ruling are entirely correct. It is impossible to validate a hadas whose leaves are arranged in a configuration of two and two, for there is no way this can be considered meshulash. Having no other choice, the Bikurei Yaakov maintains that is preferable to take a hadas whose leaves are arranged in the format of two with one above them than those arranged in a two upon two format. Those who permit the former arrangement, like the Tosafot (32b, s.v. telata), do so because they consider it to be a form of meshulash, a classification lacking for the two upon two format. So the Rema’s words require further study.
However, this is only true if we understand the need for meshulash to derive from the very identity of the species to be taken. If only a hadas with the property of meshulash (no matter whether it is defined according to Rashi or Tosafot’s definition) can be defined as anaf etz avot, then this quandary persists. A hadas with leaves arranged in a two upon two format is by definition not an anaf etz avot. However, if the purpose of taking the hadas is solely to perform the act of taking avot, then meshulash is required only to enable us to take a densely-leaved avot plant. In this case, the words of the Rema fit perfectly, for if we maintain that three leaves create a dense foliage, certainly one pair of leaves situated just above another pair – four overlapping leaves in total — will create this avot effect. So if we validate a hadas with groupings of only three leaves, certainly we should validate a hadas with groupings of four, for the latter hadas has even more leaves. In contradistinction to the Bikurei Yaakov, we would argue that a hadas possessing the leaf arrangement of two and two is superior to a hadas possessing the arrangement of two and one.
I reviewed the Rema’s original responsum (Siman 117), and this whole idea, this entire vision, is embodied almost explicitly in his words. He is asked in this responsum why the grafted etrog was invalidated, but not the grafted hadas? He responded:
Because the grafted [etrog] is neither called an etrog nor a peri etz hadar, but the hadas the Merciful One made contingent upon its possessing the characteristic of avot. Therefore, if we see an Egyptian hadas that possesses the characteristic of avot, why should we invalidate it?[14]
(Translated by Meshulam Gotlieb)   

[1] That is to say, of those species in which the plant or tree is taken to perform the commandment, and not the fruit, such as the etrog
[2] All references to the Ramban or the Ra’avad in this article refer to the Ra’avad’s Chibbur Ha-lulav and the Ramban’s Hassagot (critiques) on it, edited by R. Kapach (Jerusalem, 5710); references to Rambam refer to Hilkhot Lulav, unless specified otherwise; references to the Gemara are to Massekhet Sukka.
[3] Translator’s note: the interpretation of the import of this phrase will be the central task of this article. Suffice it to say that the word avot has been translated as leafy, thick, and plaited.
[4] Yeshayahu 41:19; 55:13; Zekharya 1:8-11; Nechemya 8:15. While one could argue that the word hadas derives exclusively from the language of the Prophets and the Scriptures, and not from the Torah, the verse cited from Nechemya demonstrates that anaf etz avot and hadas have distinct and separate linguistic roles that do not stem solely from their use in different, historical strata of the language. Absent the need to distinguish between these linguistic strata, it seems that the Torah privileged the use of the phrase, anaf etz avot, over the use of the word, hadas. In any event, as will be demonstrated, the crux of the argument that anaf etz avot describes the plant, instead of naming it, does not depend upon whether the Torah could have used the word hadas but rather upon its decision to, come what may, describe, instead of name, the plant.     
[5] We will not discuss the matter of the etrog, for this issue requires a separate discussion of its own.
[6] Ramban (p. 48) emphasizes the commonality among those elements that render all four species ritually invalid, and even draws halakhic conclusions from this. 
[7] Page 15b in the pages of the Rif, s.v. tani.
[8] Ra’avad (p.14).
[9] This quotation is cited from Milchamot Hashem (p.15b in the pages of the  Rif, s.v. ve-od) wherein the Ramban responds to the Ba‘al Ha-Maor’s approach  (ibid., s.v. tani) which is similar, although not identical to the Ra’avad’s. The Ramban’s critique in his Hassagot on the Ra’avad is similar in content, though far more tempered in tone.   
[10] In Rabbenu Manoach’s commentary this explanation is cited from the Rambam’s own responsa; however, our version of the responsum (Blau edition, #313) omits this point.
[11] In his Chibbur Ha-lulav, the Ra’avad repeats this argument; however, he also compares the hadas, lulav, and arava regarding the laws of leaves having fallen off, leaves having become separated, and so forth. See, ibid., p. 21, s.v. od shaninu be-mishnatenu, and at the top of p. 16.  
[12] See Arukh Ha-shulchan, Orach Chaim 646:3.
[13] The Meiri and the Ritva rule likewise in their discussions of factors disqualifying the species for the entire holiday (29b, on the mishna).
[14] Of course, we are not surprised to learn that many Acharonim invalidated a grafted etrog. See Sha‘arei Teshuva 646:4, and those sources cited in the Encyclopaedia Talmudit, s.v. hadas, Volume 8, p.341.