On my mother’s glass-and-chrome étagère stands a sepia-toned photograph of a dapper-looking soldier, a captain in the tzar’s army. The young man, my maternal grandfather, wears his medals and other military regalia. The picture pleases the eye, startling the viewer only when background information comes to light: In addition to being a commanding officer, my grandfather was a rabbi.I never met my grandfather, Benjamin W. Greenberg. He died several months before my birth. In compliance with Ashkenazic custom, I inherited his name. Still, having heard stories about this Renaissance man, I feel that I know him.Like many rabbis, Grandpa amassed a vast collection of Jewish books, including rare folios and classical texts. Sixteenth-century Bibles, illuminated haggadahs, and anthologies of Yiddish poems stood among the bound volumes on shelf after shelf in his modest house, which he purchased in Brooklyn after he emigrated from Russia. Simply acquiring a treasure-trove of books, however, was too conventional to satisfy his eclectic tastes. He also cherished another object. Grandpa was an avid collector of etrogs.Along with palm, myrtle, and willow, the etrog—known also as citron—is one of the four plant species required for rituals on the agricultural holiday of Sukkot. The citron looks like a large elongated lemon, but it never decays. Instead, it desiccates and shrinks over time without rotting. An unblemished, perfectly oblong citron can fetch hundreds of dollars, making it easy to envision the etrog as a precious collectible.The cancer patients I treat in my medical practice continually teach me how illness reminds us that time is precious because life has an expiration date. I find a bit of irony in the fact that the etrog gains worth, in part, because it never decomposes, never expires. Understandably, on the spectrum of Judaica that may or may not be handed down, the etrog occupies a unique niche; somewhere between permanent artifacts, such as challah knives and Torah mantles and perishables like latkes and lulavs.Grandpa’s etrog collection was not preserved by the family member to whom it was bequeathed. Still, it continues to be a source of reverie for me. I can’t help but wonder how he might have displayed his prized possessions for colleagues and friends. Would he have arranged them by color, the darkest brown fruit on the left with the newest etrog, still boasting a yellow hue, on the right? Or might he have cataloged them as a function of tactile criteria, from bumpy texture to smooth? I envision him positioning the etrogs in descending size order like the Russian nesting dolls he might have seen during his childhood. In my fantasy, I imagine him doting over his etrogs with the pride I’d like to think he’d have felt for my siblings and me, if he had been able to get to know us.What prompts people to become collectors? Obviously, some are simply fascinated by a particular object. Others establish collections for the sake of society, as a form of civic altruism. Indeed, many great collections housed in museums of art or science reflect a public service rather than a personal proclivity.Conversely, some Freudian psychologists see dark sides to collecting. For instance, when collecting is a quest, it often represents a lifelong pursuit that can never be fulfilled and instead becomes a catalyst for frustration. Moreover, there are situations when collecting reflects a need to hoard rather than have, so that collecting becomes a form of greed. But in piecing together Grandpa’s story from surviving relatives who knew him, I think that his collection was more likely an antidote to avarice.Scripture does not precisely specify the identity of all four herbal species to be employed as religious symbols on Sukkot. The use of the citron for the etrog is based on an inference derived from Leviticus 23:40: “And you shall take on the first day the fruit of goodly trees.” The interpretation of “goodly [hadar] trees” is a source of debate in the Babylonian Talmud (Tractate Sukkah, 35a). There, Rabbi Judah urges us to read the Hebrew term for goodly trees, “hadar,” as “hadeer,” a flock of sheep.The analogy tells us that, just as a flock of sheep contains older and younger animals so, too, the citron tree simultaneously supports older and younger fruit, often with years of disparity. Therefore, the etrog might be a metaphor for lineage and intergenerational co-existence as well as cooperation—qualities that could hardly comport with greediness. Thus an etrog collection, particularly one maintained by the older generation and left as an heirloom for future generations, is symbolic of the commitment of one generation to the next.At the conclusion of Sukkot four years ago, just prior to my first grandson’s birth, I did not discard my etrog. Instead, overcome by a sense of responsibility to my offspring, I resolved to save my etrogs from year to year, as my grandfather had done.Grandpa and his etrog collection are no longer with us, but their respective legacies have not vanished. In selecting the etrog as an item for collection, Grandpa may have been sending a scholarly signal to his descendants to respect each other as the family tree arborizes with time. Collecting is not only about tangible objects, but also intangible values and ideas.