Step 1 : Introduction to the question "What did George Washington grow in his greenhouse at Mount Vernon?"
...The earliest recorded mention of using greenhouses to grow plants dates to the ancient Romans. Emperor Tiberius wanted a cucumber on his plate every day, so he had special houses constructed to grow them year-round. The practice of growing crops in greenhouses spread to Holland and then to England. From there, it made its way to the New World. George Washington had greenhouses constructed at Mount Vernon so he could grow pineapples, one of his favorite foods. Source: GardenGuides.com