The “fruit of the hadar tree” that we are commanded to take on Sukkot is the etrog. The identity of the etrog is a tradition passed down from generation to generation. Just as with all fruits, there are different varieties of etrog: some large, some small, some yellow, some greenish – and all kosher.
A few hundred years ago, a serious problem arose. Since the etrog tree is delicate, sensitive, and susceptible to disease, its cultivators (most of whom were non-Jews) often grafted an etrog branch onto a lemon or bitter orange tree. Although some poskim were lenient about these etrogim, the accepted ruling is that an etrog that grows from a grafted tree is invalid. For the Torah commands that an etrog be taken, whereas a grafted etrog is considered a new being or a combination of two fruits, an etrog and whichever tree the etrog branch was grafted to (Rema; MA; Shvut Yaakov). Others invalidate it because it is the product of a prohibited action – it is forbidden to graft the branch of one tree onto the trunk of another (Levush). Nowadays, etrog growers are careful to avoid hybrids, so one can rely on sellers when they state that their etrogim are not grafted.
All etrogim start out with a pitam (blossom-end), but it usually dries out and falls off while the etrog is very small. These etrogim without a pitam are kosher le-khatḥila and are not deficient in any way, as this is how they grow. There are some varieties of etrogim that are more likely to retain their pitam. Sometimes the pitam is very robust and fleshy, and other times it is dry and woody. There is a spray that stops the pitam from drying out and falling off, and cultivators who want to grow etrogim with fleshy pitams use it.
A fleshy pitam is the same color as the etrog, and its flesh resembles the flesh of the etrog. At its tip is a shoshanta (stigma), a dry, woody flower knob. The fleshy pitam has the same status as the tip of the etrog in every respect. Any deficiency or stain that invalidates the etrog when found on its sloping top (“nose”) also invalidates it when found on the fleshy part of the pitam. With regard to the shoshanta, if it is entirely missing, the etrog is invalid, but if enough remains of it to cover the flesh of the pitam, the etrog is kosher. (See Harḥavot 4:10:7-9.)
The status of a woody pitam is more lenient. If the pitam is completely missing, so that nothing at all protrudes, the etrog is invalid. If even a tiny bit of it remains protruding from the etrog, the etrog is kosher (SA 648:7; MB ad loc. 30).
If the entire oketz – the end of the branch that joins the etrog to the tree – is missing and the flesh of the etrog is visible, the etrog may not be used for the first Yom Tov because it is deficient. If enough of the oketz remains to cover the flesh of the etrog, the etrog is kosher and may be used even on the first Yom Tov (SA 648:8; MB ad loc. 33).