Dear DirtyDishes:
In ancient Greece, oregano was called "joy of the mountain", taking its name from "oros", meaning mountain, and "ganos", meaning joy. This wild herb favors hilly terrain and its root structure helps bind the soil and keep it from washing away on steep slopes.
It is difficult to trace oregano's history because of this herb's relationship to its cultivated cousin marjoram. Both are of the same genus, and their popular and botanical terms have long been confused. It seems, however, that in ancient times oregano was not as widely used in cooking as was marjoram, except along the Mediterranean coast. There, cooks recognized its affinity for tomato based sauces, lamb, seafood and almost any garlic flavored dish, and it became a culinary tradition to use oregano in many dishes.
In the Americas, cooks in Mexico used oregano to flavor chile based dishes but in North America, cookbooks rarely mentioned oregano until after World War II. Then, returning GIs brought back the love for pizza, and oregano was discovered in the US. Suddenly there was an explosion of interest in oregano. From an herb that the Department of Commerce did not list separately in import reports due to the low consumption volume, oregano use grew to one and a half million pounds a year by the 1960s and has since grown to over fourteen million pounds.
Oregano that comes from the Mediterranean is known as "Origanum vulgare", meaning it is a wild species of the genus "Origanum". Marjoram (Origanum majorama), is a member of the same genus. Some refer to oregano as a "wild marjoram", but marjoram is, in fact, a cultivated species of "Origanum".
Long-established trade practices also recognize the leaves of certain Mexican plants as oregano, since their flavor and aroma bear a resemblance to Mediterranean oregano. Mexican oregano, however, is from the genus "Lippia", quite distinct from "Origanum". Species used in Mexico today are "Lippia graveolens" and "Lippia berlandieri".
For many years, Greece was the leading source for the US of Mediterranean oregano. Currently, Turkey is by far the leading supplier of oregano to the US market, followed by Greece and Israel. Though Italy harvests a great deal of oregano, it uses so much domestically that very little of it is exported. As compared to the Mexican variety, the Mediterranean oregano is a smaller leaf of lighter green color and milder, sweeter flavor. Compared to sweet marjoram, however, it is stronger and has a slightly lemony taste. Mediterranean oregano typically has a minimum of 2% essential oil. Mexican oregano is a much stronger, robustly flavored herb, which is the result of having a higher essential oil content of around 3%-4%. Its leaves in their original form are larger and a darker shade of green.
Consideration of the intended use is the key to buying the right type of oregano. When deciding between the Mediterranean and the Mexican types, the question is not which is better, but rather which flavoring effect is desired. If you do not want the oregano flavor to overwhelm the tastes of your other flavors in the dish, you will probably use the Mediterranean oregano.
Oregano should be stored in tightly closed containers and kept in a cool and dry place. Excessive heat robs it of flavor, and dampness tends to cause caking.
I hope that this is of assistance.
what is this plant, and what can I do with it? 
