It's not exactly accurate that I've never used culantro before; many years ago, a local farmer brought me three tiny leaves to play with, leaves that were much smaller than these. He was trying to grow it for me, but apparently, the herb is very tough to germinate and doesn't really care for our climate here in Virginia. Nonetheless, I wanted the guys on the crew to play with this cilantro-flavored herb from Mexico and Central America that often goes by its Puerto Rican name, recao. I've also heard it called sawtooth herb, a name that it comes by quite naturally as you can see in the photo.
Culantro and cilantro are almost interchangeable in cooking, but culantro is more pungent. I like culantro for cooked applications because the leaf is a lot sturdier. It is especially at home in the sofrito (seasoning base) called recaíto that is the basis for a lot of Caribbean and Central American dishes.
The rest of this bunch went into the various dishes for which we use cilantro.
Vote: As long as culantro is a lot more expensive than cilantro, we'll keep on using cilantro.