Some history and some speculation...

The saga of Jefferson and his favorite herb, tarragon, is a typically exasperating story of failure and futility. Jefferson likely encountered tarragon, or estragon, while in Paris as minister to France. After returning home in 1793 he wrote his French neighbor Peter Derieux that it "is little known in America." Perhaps because of tarragon's noticeable absence from the French cuisine at the President's House, Jefferson in 1805 asked J.P. Reibelt, a Swiss book dealer in New Orleans, to procure him seed. The genuine tarragon used for cooking and vinegar rarely produces seed but is easily propagated from root divisions. Jefferson never realized this, and his fervent search for the seeds is a key reason tarragon may never have been established in the garden. By 1813, after various plantings of roots, plants, and seeds, Jefferson reported tarragon in both square XVII and in the submural beds below the garden wall. These were seed-propagated plants from steamy New Orleans and were more likely what is today called Russian tarragon, an inferior sort that mimics but fails to match the sweet, liquorice-like flavor of the genuine article.
Peter J. Hatch. A Rich Spot of Earth: Thomas Jefferson's Revolutionary Garden at Monticello

And so for day 2104