Coriander versus cilantro: the confusion continues.

Things I learn... I thought I knew that coriander (the dried herb) and cilantro (the fresh leaf), both came from the same plant, but that Europe doesn't distinguish between the two, calling them both coriander. However, I was flipping through On Food and Cooking just now, and discovered that the reason why Americans call fresh coriander cilantro is because there's a Central and South American herb called culantro (Eryngium foetidum), which tastes much like the Middle Eastern herb, coriander (Coriandrum sativum), and has mostly been displaced by it throughout Latin America. So odds are good that your guacamole was made with coriander. But to add another twist to the story, culantro lives on. It's still sometimes used in Latin America, but it has been enthusiastically adopted by Asia, especially the Vietnamese, who use the leaves as a substitute for Vietnamese coriander, Persicaria odorata (which is neither a coriander nor a culantro). So your cilantro is probably coriander, unless you're eating Vietnamese, in which case it might be culantro, or something else entirely. As a side note, the unpleasant "soapy" flavor that some people are sensitive to is the result of a fatty aldehyde, decenal, also present in citrus peels. So if you don't like cilantro, you probably won't like citrus zest, or citron, the much-maligned fruitcake ingredient. (Then again, why are you eating fruitcake, when you could be eating this?) It's not present in the seeds, however, so most people who hate the taste have no problem eating coriander heavy cuisines such as Indian. It's also heat sensitive, so it's possible that lightly cooking the cilantro would drive off the offending soapy component. However, most of the other flavor compounds in cilantro are even more volatile, so it'll probably just taste grassy. Try it at your own risk.