"Ugh," my sister exclaimed one evening as we were making dinner. It was supposed to be an easy poached chicken with a ginger-scallion sauce, eaten with cold cucumber wedges, and we had just discovered that what we had bought at the store was not cucumber, but zucchini. It was an easy mistake to make — they were the precise same shade of green. But where the zucchini's skin was mostly smooth, the cucumber's was lumpy. We were not happy.