Chestnuts are the fruits of several species in the Fagaceae family. They are yummy when roasted and you can use them in many dishes. Additionally, the French use them to produce a sweet paste (crème de marrons) and yes, you guessed right, you can make flour out of them.
But, read the first sentence again: Chestnuts are tree fruit. And tree fruits are not included in the minhag of kitniot (as we already determined when discussing coffee beans). End of discussion. I haven’t found chestnuts on any list. The question is not very often ask, but authorities (Rav Peretz Moncharsh) and social-media-users (comments by imaleader and Ziner on April 02, 2001 at 04:02 PM and 04:20 PM, comment by LuvMyGirl on April 03, 2001 at 08:51 AM) agree that it is not kitniot. This level of agreement is astonishing!
So where did I get the idea from that they might be kitniot? Aish has the sentence "Some things like chestnuts […] were not included in the original prohibition of kitniyot." (Aish: All About Kitniyot) – implying that it is now included. But apparently they are the only ones who think so, so the rest of us – enjoy.
- Danger of chametz traces: No.
- Danger of confusion with chametz (raw): Definitely no.
- Danger of confusion with chametz (processed): Haven’t seen the flour. The paste, no.
- Botanical categorization: Fagaceae (beech family, tree).
- Known in 13th century: Yes.
- Verdict: Not kitniot.
photo (c) Fir0002/Flagstaffotos