In an 1893 case heard by the U.S. Supreme Court, John Nix brought suit against the State of New York, claiming that he shouldn't have to pay vegetable tariffs on imported tomatoes since tomatoes are a fruit, not a vegetable. The court eventually concluded that because tomatoes are used as a vegetable then they counted as such for tax purposes. Although they don't go as far as the Supreme Court, debates continue today about what counts as a fruit and a vegetable.
When considering which seeds count as fruits and which as vegetables when planting your garden, it is essential to first understand what constitutes a seed. Seeds develop after sexual reproduction combines the genetic material of two parent plants. In addition to the plant embryo, seeds contain a protective covering and a nutritive substance to support the developing seedling, according to biology professor John W. Kimball. Many food crops, such as potatoes and garlic, are planted from bulbs or tubers, not seeds.
Modern thought often places fruits and vegetables at odds with each other. A food can belong to one but not both. Botanically speaking, a fruit develops from the wall of a plant's ovary and encases the seeds, so back in 1893, John Nix was right: Botanists consider tomatoes a fruit, not a vegetable. By this definition, many common garden seeds, including tomatoes, pepper and cucumbers are not vegetable seeds at all, but fruit seeds.
Professor Marvin Pritts of Cornell University defines a vegetable as "anything that is not reproductive," which includes stems, leaves and roots. From a botanical perspective, again, this definition makes sense, as vegetative reproduction and growth are terms that refer to plant development that does not result from sexual reproduction. From this perspective, seeds that grow crops where you consume parts not involved in reproduction--lettuce leaves, celery stems or carrot roots--count as vegetable seeds.
To throw another loop into the classification of seeds, the U.S. Department of Energy's Ask a Scientist program adds a further distinction between vegetables and herbs. They define herbs as the leaves of plants, so using this definition, basil seeds and lettuce seeds would be herb seeds.
However, as Dr. Pritts points out, people other than botanists answer the question differently. As revealed in the Nix v. Hedden case, cooks define fruits and vegetables based on their use in foods, so when you plant tomatoes or eggplants, you are still planting vegetable seeds. Pritts also suggests that some gardeners consider annual plants as vegetables and perennials as fruits. By this reasoning, tomatoes, corn and squash are all grown from vegetable seeds, while strawberries, blueberries and apple trees are grown from fruit seeds.