Though the text speaks of the first day, the sages explained that the four species were to be taken on each of the seven days, but not on Shabbat, even if this falls on the first day of the festival.
THE LULAV – The lulav (the rod-shaped shoot of the date palm) is the spine of the four species.
It must be at least 4 handbreadths (about 40 cm) long (excluding the frond of leaves on top), but a 3-handbreadth lulav is still acceptable and a b’rachah may be said over it.
A lulav is not kosher if most of its leaves or the stem are dried out, if most of the leaves are severed or separated (even if the top leaf is intact).
THE ETROG – The Torah does not call the etrog by that name. It says, “Take for yourselves… the fruit of a hadar tree” (Lev. 23:40). Many translations render hadar as goodly, since hadar in other contexts means splendour. By tradition, the fruit the Torah is speaking of is the citron or etrog.
It is not valid if the button-like tip (pitom) is missing, though some valid types of etrog grow without a pitom. Etrogim must be pure, not grafted (mur’kav).
Historically, etrogim tended to come from Corfu, but by the latter part of the 19th century there were fears that grafting was practised in Corfu and in 1876 Rabbi Yitzchak Elchanan Spektor of Kovno, joined by Rabbi Yisrael Salanter and other rabbis, insisted that etrogim be obtained from other sources. Thenceforth Corsican etrogim were used.
A problem arose when, because they had a captive market, some suppliers inflated their prices; in addition, the early Zionist colonists in Israel urged that their etrogim should be used. Rav Kook authorised Israeli etrogim provided the growers guaranteed that there was no grafting and that supervisors oversaw the production.
Grafted etrogim tend to have a smooth skin as opposed to the bumpy skin of non-grafted etrogim and have a thin skin and a juicy interior whereas the non-grafted fruit is thick on the outside with a rather dry inside.
An etrog should not be smaller than an egg, though some scholars believe eggs are now smaller than in the time of the Talmud and they make the minimum size the equivalent of two eggs.
After the festival, etrogim go back to being merely citrons, hence the saying Esrogim nach Sukkos (something that has come too late).
THE HADASSIM (MYRTLES) – Hadassim must be at least 3 handbreadths (about 30 cm) long excluding the leaves, but they should not be less than approx. 10 cm shorter than the lulav.
Myrtle leaves grow in groups of three along the branches, and hadassim need to consist of at least three myrtle twigs.
They are invalid if all the leaves are dried out or if there are more red or black berries than leaves, though the berries may be removed before the festival.
THE ARAVOT (WILLOWS) – Aravot, which usually grow near rivers, must be at least 3 handbreadths (about 30 cm) long excluding the leaves. Two willow twigs are necessary.
Aravot are invalid if most of the leaves are dried out, severed or split. It is usual to look for willows which have the top leaf intact.