A bent Lulav:[1] 

A. Spine is bent:[2]

The middle of the spine is bent: If the spine of the Lulav is bent towards its front making it appear like a hunchback, it is not kosher.[3] Similarly if it is bent to its side it is invalid.[4] If the middle of the spine is bent towards its back, meaning towards the side of the spine, it is kosher.[5]  

The top of the spine is bent: If the middle of the spine itself is straight while the top of the spine is bent like a Hegmon, the Lulav is invalid. This applies whether the Lulav is bent backwards or forwards.[6]

 

Summary:

A bent is always invalid unless it is bent backwards towards the middle of the spine.

 

B. Leaves are bent:[7]

If bent on the top of the leaves: If majority of the leaves of a Lulav are slightly bent or curved at their top it may not be used unless there is no other Lulav available, in which case it may be used with a blessing. If only a minority of its leaves are curved it may be used even Lechatchilah.

If bent in the middle of the leaf:[8] If [majority] of the actual leaves [not just the top] are very bent in a way that each leaf appears like two leaves, the Lulav is invalid according to all.[9]

On Chol Hamoed:[10] Even if majority of the leaves are bent or curved it is kosher even Lechatchilah.

Second day of Yom Tov in Diaspora:[11] If majority of the leaves are bent or curved one may use the Lulav if no other Lulav is easily available.[12]

 

Q&A

What is the law if only the Tiyomes is bent?

From Admur it is implied that the Lulav remains Kosher according to all opinions if majority of the leaves are not bent, even if the Tiyomes is bent. However see M”B 645/33; Kashrus Daled Minim p. 105.

 

Kneplach-Rounded tips:[13]  

Based on the above the top leaves of the Lulav should not have rounded tips known as kneplach.

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[1] 645/18-20

[2] 645/18-19

[3] 645/18

The reason: As this is not considered Hadar. [ibid]

[4] 645/18

The reason: As this is not considered Hadar. [ibid]

[5] 645/19

The reason: As this is the way a Lulav grow and this is its beauty. [ibid]

[6] 645/19

The reason: As this is not considered Hadar as it is not usual for the head of the spine of a Lulav to be bent backwards or forwards. [ibid]

[7] 645/20

Background:

Admur records a dispute on this matter: The first opinion rules that if the spine is straight the Lulav is Kosher even if all its leaves are bent on its top, including if the Tiyomes is bent. The reason for this is because this is the common way for many Lulavim to grow. Others rule that if majority of its leaves are bent on their top it is invalid. Practically Admur rules that initially one is to be stringent not to use such a Lulav although if no other Lulav is available he may be lenient. [ibid]

Other Opinions: Some are particular to follow the Rosh to purchase specifically a Lulav with bent and rounded leaves as this secures the Tiyomes. [Piskeiy Teshuvos 645/14]

[8] 645/21

[9] The reason: As this is not considered Hadar. [ibid]

[10] 649/19

[11] 645/20

[12] The reason: As since the Mitzvah of Lulav is only Rabbinical on the second day therefore one may be lenient if there isn’t a non-bent Lulav readily available.

[13] Sefer Haminhagim; See M”B 645/40 and 42