The table is set; your Seder plate is ready, and on it is everything you need: the matzos, the “shank bone,” the hardboiled egg, the “bitter herb” of a horseradish root, the ḥaroset or sweet condiment, and the karpas or celery. Or is it parsley? Of course, Jews wouldn’t be Jews if they agreed about everything, but why can’t they agree about this? Why do some of us use parsley and some of us celery when we all call it by the same Hebrew name?
The fact is that karpas, whatever it is, doesn’t have to be on your Seder plate at all, and in some families and traditions it isn’t. In instructing the Israelites how to consume their last dinner before departing from Egypt, the book of Exodus has God tell Moses: “And they shall eat the flesh [of the paschal sacrifice] that night, roast with fire, and unleavened bread; and with bitter herbs they shall eat it.”
There’s nothing about leafy greens. These originated much later in the custom, referred to in the third of the Four Questions, of twice during the Seder dipping a vegetable in salt water and eating it — and at first, this vegetable was identical with the bitter herb, which doubled in both capacities.
The Mishnaic tractate of Pesachim, which deals with the laws of Passover, lists the edible Palestinian plants that were considered bitter enough to qualify for the job. These were ḥ azeret, which in the Hebrew of that age meant lettuce (although not all varieties of lettuce today have a bitter aftertaste, in antiquity they probably all did); ulshin, which has been identified as either chicory or endives; tamkha, a Mediterranean root vegetable that was probably what is known in English as black salsify; ḥ arḥ avina, also a root, apparently eryngo, and maror, which in the Hebrew of the Mishnah denoted the sow thistle, an annual with bitter stalks and leaves.
This list makes one ask a few questions. If ḥ azeret once meant lettuce, why in contemporary Hebrew does it mean horseradish? Why is maror, the “bitter herb” of the Bible and the sow thistle of the Mishnah, represented on our Seder plate by horseradish? Why isn’t karpas on the Mishnah’s list at all? And why isn’t horseradish on it either?
Actually, horseradish isn’t even on all Seder plates. Throughout the Middle East, from Persia to Morocco, the bitter herb took the form — and still takes it among the descendants of Jews from these lands — of lettuce leaves, horseradish being unknown. And here lies the key to the whole problem, for once we take this into account, we can hypothesize the following historical process:
1) In Mishnaic times, when the Jewish people was still concentrated entirely around the Mediterranean and in the Middle East, a single plant was used both for the bitter herb and for dipping in salt water, so that it alone was on the Seder plate. Some Jews used root vegetables like black salsify, others used leafy vegetables like lettuce.