"The greatest service which can be rendered any country is to add a useful plant to its culture."
- Thomas Jefferson
Thomas Jefferson gave us the Declaration of Independence but he was also passionate about developing a strong and innovative agriculture in the new nation. He searched high and low for new food plants that would flourish in American gardens and on American farms. On a trip to Lombardy, Italy, he even filled his pockets with rice—risking arrest for smuggling—so he could carry it home and try it out in South Carolina. It did not thrive. Jefferson believed agriculture was the "surest road to affluence and best preservative of morals."
Thomas Jefferson was a dedicated gardener and farmer, and his interest in agriculture is evident in much of his writing. His home, "Monticello," included vegetable gardens, flower gardens, orchards, vineyards, grain fields, and ornamental landscapes.
Tended by elderly slaves under Jefferson's supervision, the garden served as both a source of food for Jefferson's family and a laboratory where Jefferson experimented with 330 varieties of more than 70 species of vegetables from around the world. Plants in the garden included squash and broccoli imported from Italy; beans and corn collected by the Lewis and Clark expedition, figs from France, and peppers from Mexico. The English pea was his favorite vegetable.
He had a Garden Book in which he kept detailed notes on his turnips, lettuce, artichokes, tomatoes, eggplants and squash. He recorded when each variety was sown, when it was mulched and how, when the first leaves or fruits appeared, when the they came to the table and which varieties were tastiest. His Garden Book provided a model of the scientific method at work, written at a time when American horticulture was in its infancy. He applied his analytical mind to gardening, writing that "I am curious to select one or two of the best species or variety of every garden vegetable, and to reject all others."
Some of the varieties that Jefferson cultivated at Monticello have been passed down as heirloom vegetables, and people still plant them in their backyard gardens. Overall, he had about 5,000 acres of farmland, planted mostly in wheat and other grains.
Introduced Plants: More Harm than Good?
Thomas Jefferson was passionate about introducing "useful plants" to the new nation. His garden contained plants collected from around the world. Some came from friends at home and overseas and some he collected himself while he was traveling in Europe. He planted some of the seeds he collected in his own gardens, but he also passed seeds along to friends and neighbors, family members, and to some of the leading plantsmen of the early 19th Century. Many of the vegetables grown at Monticello were rare for their time—asparagus bean, sea kale, rutabaga, lima beans, okra, potato pumpkins, winter melons, cayenne pepper, black salsify, sesame, eggplant. Even tomatoes were considered exotic during Jefferson's time. He served them in his home and encouraged people to try them, even though some considered them dangerous.
Jefferson is admired for introducing new plants, but today we know that some introduced plants can have a negative effect on an ecosystem. Introduced species can become pests, bullies, and weeds. This was not so much a concern in Jefferson's time because gardens back then were mostly free from insect pests, disease and weeds introduced from other parts of the globe. Early Americans had weeds in their gardens, but they were not as much a threat to ecological and horticulture harmony as invasive plants are today.
Introduced species are species that have been introduced into areas outside their natural ranges. Throughout history, 50,000 nonnative species have been introduced into North America. Many of these species, such as wheat, rice and peaches, were introduced as sources of food. Introduced species —plant and animal— provide more than 98 percent of the food we eat today.
In Jefferson's time the most troublesome weeds were native. Today it is plants introduced from other parts of the world that cause the most problems. Only 15 percent of our worst weeds are North American natives. The majority originated in Europe or Asia. Humans have always carried species from one region to another and between continents, but the development of rapid means of transportation has greatly increased the frequency of such introductions.
For an introduced species to be considered invasive, the negative effects must outweigh any benefits. Introduced species that become invasive are a threat to biodiversity. Almost half the species in the US that are at risk of extinction are negatively impacted by invasive species. Invasive species threaten biodiversity in several ways.
They out-compete native species for food and natural resources.
They may hybridize with local species so that within a few generations, few if any genetically pure native individuals remain.
They may exploit a resource that native species cannot use, which allows them to take hold in the new environment.