1) I do not see where the Gemara or Rashi on 33b sounds like Mesaken Maneh is d'Oraisa. Rashi already wrote on 33a that if one makes Hadasim fit for the Mitzvah, this is not Mesaken Maneh d'Oraisa but only d'Rabanan. This is presumably because Mesaken Maneh d'Oraisa means making an actual Kli. (For example, one who makes a table on Shabbos transgresses a Torah prohibition because he made a practical, physical utensil. In contrast, if one made Hadasim fit for the Mitzvah, he did not actually make a Kli, because one cannot use it for physical work. However, since one can do a Mitzvah with it, it is similar to making a Kli, which is why it is forbidden mid'Rabanan.)

2) Therefore, on 33b, when the Gemara asks that removing leaves from the Hadas on Yom Tov should be forbidden according to Rebbi Eliezer b'Rebbi Shimon because of Mesaken Maneh, it is not necesary for Rashi to tell us again that this is only a Rabbincal prohibition, because he already told us that on 33a.

3) I found that one of the Rishonim, Rabeinu Avraham Min ha'Har, on Sukah 33b writes about the question of the Gemara that Rebbi Shimon agrees that a Pesik Reisha is forbidden, and says that we see from here that a Pesik Reisha is forbidden even for an Isur d'Rabanan. One learns from Rabeinu Avraham Min ha'Har that the fact that the Gemara uses the terms "Davar she'Eino Miskaven" and "Pesik Reisha" does not mean that we cannot be talking about Rabbinical prohibitions.

4) Daniel, even though I have answered for Rashi's Shitah, I found that you were Mechaven, Baruch Hash-m, to other Rishonim.

a) The Me'iri (Shabbos 29b, DH v'Yesh Mosifin; see also Me'iri to Shabbos 41b, DH Meicham) writes that it may well be that when the Gemara states that Rebbi Shimon agrees about a Pesik Reisha, this refers only to a Torah prohibition. The Me'iri questions his own reasoning from our Gemara which says that Rebbi Shimon agrees in the case of a Pesik Reisha, even though the Tikun Kli of the Hadas is only mid'Rabanan. The Me'iri answers that possibly we say that Tikun Kli is d'Rabanan only where the scenario is one where one does not do an action. For instance, when one separates Terumos and Ma'asros one is not doing a Ma'aseh. The "Hashlamah" (cited in note 398 to the Me'iri on Shabbos 29b) explains that when one separates Terumos u'Ma'asros he does not effect a physical change in the food. Rather, he simply moves some of the fruit to the other side of the pile. In contrast, when one removes the berries of the Hadas one is causing a physical change in the Hadas. Therefore, according to the Me'iri, removing the berries from the Hadas in order to make the Hadas fit for the Mitzvah is considered a Torah prohibition.

b) The dispute between Rashi and the Me'iri, may be reflected in another dispute, which is very relevant to practical Halachah. This is the dispute between the Magen Avraham (Orach Chayim 314:5) and the Terumas ha'Deshen (which the Magen Avraham there cites). The Terumas ha'Deshen maintains that one is permitted to do a Melachah d'Rabanan on Shabbos if one does it in the way of a Pesik Reisha. The Magen Avraham disagrees and maintains that a Melachah d'Rabanan done through a Pesik Reisha is also forbidden.

It seems that the Magen Avraham sides with Rashi, while the Terumas ha'Deshen sides with the Me'iri. Therefore, according to Rashi and the Magen Avraham, our Sugya in Sukah 33b is discussing doing a Melachah d'Rabanan through a Pesik Reisha, which is also forbidden, while the Me'iri and Terumas ha'Deshen maintain that our Sugya is discussing specifically doing a Melachah d'Oraisa through a Pesik Reisha.

c) The Mishnah Berurah (OC 314:11) writes that the Eliyah Rabah, Vilna Ga'on, and Rebbi Akiva Eiger agree with the Magen Avraham.

Kol Tuv,

Dovid Bloom

1) I saw that the Pri Megadim (Mishbetzos Zahav 654:1) learns a different Peshat in Rashi than what I cited above. He explains the words "d'Tarach l'Tikunei Mana," which Rashi uses to describe the prohibition against changing the water, disposing of the old water, and filling up with fresh water, and then returning the Lulav to the water. He gives two possible ways of understanding this:

(a) It looks as if he is intending to do Tikun Mana.

(b) This is considered "Tircha Yeseira," over-exertion, which is prohibited on Shabbos.

2) For the moment, I will try to explain (b). We should first point out that it seems obvious to the Pri Megadim that when Rashi uses the words "Tikunei Mana," this cannot be taken literally to mean that putting a Lulav in water is forbidden because of Tikun Mana. This is because "Tikun Mana" means that one made a utensil on Shabbos which is forbidden, but one cannot say that merely watering a Lulav is like making a Lulav. Therefore, Rashi says that one may not change the water because this is too similar to hard work.

To be honest, I have a feeling that the Pri Megadim is consistent with what he writes in the other place in Shulchan Aruch where the prohibition against adding water to a vase of plants is mentioned. This is in Hilchos Shabbos, in the Magen Avraham 336:13. The Pri Megadim, on that Magen Avraham, writes that if the water is already there, one may put the Lulav in it on Shabbos. What is forbidden is to draw the water from one vessel to another, because this is a Tircha.

3) I personally have a hunch that the Pri Megadim is referring to drawing water out of the well. This is what he means when he writes in #654 that this is over-exertion. The Pri Megadim is cited by the Mishnah Berurah (OC 336:54) as a lenient opinion. The Mishnah Berurah does not allow us to rely on the Pri Megadim l'Chatchilah, but in Sha'ar ha'Tziyun #48 he writes that possibly one may rely on the Pri Megadim if one forgets to put plants in water on Erev Shabbos, and the flowers are of the type that do not open up as a result of being put in the water.

I am still in the middle of this Inyan but I must close here for the moment.

Dovid Bloom