The plural of asparagus is an interesting lesson in language. The word, in fact, could be said to not actually have a plural, or to have two plurals, depending on your viewpoint.
Several possible derivations have been proposed for our English word Asparagus. Asparagus is a Latin word which derives from the Greek word asparagos, which referred to all tender stalks or stems. This word was possibly related to the Greek word spargan meaning ‘to swell’ and the Greek word spharageomai, meaning ‘full to bursting.’ In Latin, the plural of Asparagus is asparagi.
However, don’t go thinking you’ll sound more intelligent if you refer to a serving of asparagus spears as asparagi. This is incorrect English! Since asparagus is a borrowed word in English, and not a foreign word, it needs not follow Latin plural forms. So, the plural of asparagus is not asparagi, unless you are speaking Latin. You are probably not speaking Latin.
Asparagus was used as an English word as early as the eleventh century but subsequently disappeared. It reemerged in the mid-1500’s in forms such as sperage, sparage and sperach. Botonists and other scholars, however, went right on using asparagus in books and it was reintroduced for the vegetable, only to be turned into sparrow-grass, a made-up word that simply sounded better to English speakers. Asparagus, of course, has nothing to do with sparrows. By the mid-1800’s, asparagus had been accepted again by common folk. Folk-styled forms of the word still survived, however, such as the rural aspergrass and even aspirin-grass.
English Plural of Asparagus
Most sources seeking to explain the plural of asparagus greatly overthink the answer. As the word is a Latin word borrowed straight into English, it is not necessarily subject to Latin rules. Those claiming that asparagi is the plural of asparagus are incorrect, as mentioned above. However, this does not mean the plural of asparagus is asparaguses.
In English, not all words are pluralized the same. Asparagus is, in essence, already a plural word. Asparagus is not pluralized like words that are considered count nouns. These are objects that are normally counted. Therefore, the plural of apple is apples, and the plural of carrot is carrots. Asparagus spears come in groups, however, and tends to be sold in bunches. This makes asparagus more like a mass noun. Mass nouns are normally things which are an undifferentiated whole and difficult or impossible to count. These are words like wood and trash.
Before we move on, keep in mind that words that are normally count nouns can become mass nouns, or can be used as both in different contexts. For example, when more than one carrot is grated or chopped for use in a recipe, you may find them referred to as grated carrot or chopped carrot, although in the U.S. we still tend to say grated carrots more often than grated carrot.
Asparagus spears can obviously be counted, but we do not tend to count them and instead tend to refer to them in groups. Therefore, we say ‘a bunch of asparagus’ not a bunch of asparagus’s or some other form. So, when we say asparagus, we are referring to a group item, and we already mean “more than one spear of asparagus.” The word asparagus means the same as ‘some asparagus’ or ‘some spears of asparagus.’
If you tell someone you are going to have asparagus for dinner, they are, of course, going to assume you are having more than one spear!
In U.S. English the same rule that applies to asparagus applies generally to leafy or stalk vegetables. British English agrees with American English in some but not all instances.
For example, in U.S. English the plural of lettuce is lettuce when referring generally to the vegetable. We might say “some lettuce” or just “lettuce” meaning “leaves of lettuce.” To refer to multiple units of an entire “plant” we say “heads of lettuce.” The same is true of leafy vegetables and stalk vegetables in general, such as spinach, kale, broccoli, cabbage, celery, rhubarb, etc. In British English, lettuces and cabbages are used as plurals, although broccolis is not. For more discussion of this often confusing subject see the excellent answers on stack exchange.