THE SHULCHAN ARUCH (REMA) IDENTIFIES several non-grain species as off limits for Ashkenazic Jews during Passover. These include mustard, lentils and peas. Two primary characteristics are used to describe kitniyot: 1) they grow in a pod and 2) they are ground into flour. These traits are not absolute, and certain exceptions are made, prohibiting items that do not share these characteristics, and permitting others even though they fall under these categories.
An example mentioned by early halachic codifiers (poskim), is that certain types of kimmel (caraway) are considered kitniyot. However, kimmel embodies neither characteristic. On the other hand, it is customary to use potatoes and cottonseed oils (except in Jerusalem) despite the fact that they are ground into flour. Peanuts were widely used in
Russia despite the fact that they embody both characteristics of kitniyot. In addition to kitniyot, poskim have cautioned against using foodstuffs that may be grown as an alternate crop to chametz grains or those that may be processed in close proximity to chametz. Such foodstuffs were prohibited in certain Sephardic communities as well over the concern of an admixture.
Quinoa is a plant very similar in appearance to spinach. Commercially, it is not used as an alternate crop, and is never harvested with wheat. It even grows in different climates from those ideal for wheat. Industrially-packaged quinoa is processed on dedicated equipment, with no chance of contamination. However, retail-packaged quinoa may share equipment with chametz grains. Similar to other kinds of kitniyot, quinoa is commonly milled into flour.
Kitniyot is a category with certain ambiguities. Local custom and tradition therefore play an important role in determining what is, and what is not, treated as kitniyot. Since quinoa was not used in Jewish communities in generations past, we do not have a precedent to refer to. The OU has not taken a position about the use of quinoa on Passover and believes that this decision should be made locally. The information in this article is intended to enable an informed and enlightened conversation.