Does fresh produce eliminate? In other words, does your lettuce continue to breathe, process oxygen, and produce waste products? I have often noticed a bitter, for lack of a better word, organic chemical taste on lettuce, apples, and other produce. The appearance and relative strength of this taste appears to correspond with the length of storage time, etc. I’ve always assumed that this is the result of (relatively–can’t be good for you) harmless waste produced by the living plant and that the only solution (which always works) is to rinse the produce thoroughly. This debate was touched off by a visit to my Mum’s house–bitter lettuce in a salad, which I proceeded to wash, was asked why, gave explanation as per above, was given lecture on the One True Virtue of Iceberg Lettuce, that it doesn’t have to be washed as it doesn’t contain any sand. Am I hallucinating here?
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–Steven “Now I Know Why I Never Ate Salads as a Kid” Paiano
Some metabolic processes continue in dead vegetables, such as respiration, conversion of starch to sugar (in potatoes), etc. However, these processes are pretty much a yawn. Let’s stick with elimination. Do living vegetables or, to put it more broadly, living plants excrete? Not necessarily in the sense that animals do. But like all other organisms they process certain inputs and produce certain outputs, some of which we may characterize as waste. Figuring out where the waste went puzzled some early naturalists. In the late 18th century, the pioneering naturalist Erasmus Darwin (grandfather of Charles) wrote, “Others have believed [the leaves to be] excretory organs of excrementitious juices, but as the vapor exhaled from vegetables has no taste, this idea is [not] probable.” But there may be something to the notion that leaves perform an excretory function, as we shall see.
