Question:
Many people know that there is a custom to avoid nuts on Rosh Hashanah. Does this custom include pine nuts, and should they be avoided?
Answer:
The original custom recorded in the Poskim was to avoid specifically Egozim and Luzim, which refer to particular types of nuts. From a botanical perspective, there is room to distinguish between a true nut, such as a hazelnut, and a pine nut. A hazelnut is a genuine tree nut, while a pine nut is technically a seed taken from a pine cone and is not considered a true nut botanically.
Nevertheless, the widespread custom today is to avoid all foods commonly referred to as nuts, even if they are not technically nuts according to botanical classifications. Thus, just as many communities avoid almonds and even peanuts, despite the fact that peanuts are legumes and not nuts, so too pine nuts are generally included in the custom and are avoided on Rosh Hashanah.
It should be noted that this custom does not extend to ordinary seeds. Therefore, foods such as sesame seeds, pumpkin seeds, chia seeds, and similar items are not known to be included in the Rosh Hashanah custom of avoiding nuts.
Conclusion:
Strictly speaking, pine nuts are not true nuts but rather seeds. Nonetheless, because the contemporary custom is to avoid virtually all foods classified as nuts, similar to the way many avoid almonds and peanuts, pine nuts should likewise preferably be avoided on Rosh Hashanah.
Sources:
Admur 583:2; Magen Avraham 583:4; Pri Megadim A.A. 583:4; Mateh Ephraim 583:3; Kaf Hachaim 583:27; Machatzis Hashekel 583:4; Piskei Teshuvos 583 footnote 37 that the widespread custom is to avoid all nuts, including almonds and peanuts; Nitei Gavriel 28:14.