Buckwheat (Buchweizen) is a plant from the knotweed family. It is not a grain cereal, but is used as one, thereby belonging to the category of pseudocereals – remember yesterday’s discussion about quinoa.
Buckwheat is different from quinoa in one crucial aspect – it was known in 13th century Europe and explicitly included in the minhag (kashrut.com give as sources Beis Yosef O.C. 453, Rema 453:1 & 464:1 and Mishnah Berurah 453:4, 7 & 11).
Buckwheat is often used in Eastern Europe. Apparently some sort of porridge that is called kasha is made out of it. In English, the word kasha only refers to the dish made out of buckwheat. But interestingly, kasha can not only be made out of buckwheat, but also out of the five grains. So this may be a reason for prohibiting buckwheat. If someone sees his neighbour making buckwheat kasha, we have danger that this person goes home and eats wheat kasha (real chametz)! I am not sure what the relevance is when we can get kosher-le-pessach noodles or pizza – but let’s stop here. You can also make flour out of buckwheat, e.g., to make French crepes.
Buckwheat doesn’t seem to be much of a discussion at the moment. The OU list contains buckwheat, the Star-k list and the Kashrut.com list both have buckwheat and kasha. I have found only one blog that claims that buckwheat is not kitniot, but unfortunately without a source: "But while some authorities consider buckwheat to be kitniyot, others (including our congregation’s rabbi) say that it is not, and thus may be eaten during Passover." (Cheese aisle)
- Danger of chametz traces: Don’t know.
- Danger of confusion with chametz (raw): No.
- Danger of confusion with chametz (processed): Yes, as flour or kasha.
- Botanical categorization: Pseudocereal, knotweed.
- Known in 13th century: Yes.
- Verdict: Kitniot.
photo (c) Mariluna