Heather was the first to get the reference, which is to the Prologue of Chaucer's Canterbury Tales. Here are the first four lines of it:
Whan that Aprill, with his shoures soote
The droghte of March hath perced to the roote
And bathed every veyne in swich licour,
Of which vertu engendred is the flour;
Now, for the answer. The root percing drought is in the month of March. March is of course followed by April. Aprile is the name of the great wine on Michael's list, a Super Tuscan-styled Napa gem. As of last week, it was set off on his list all by its lonesome. Choose this orphan on your next visit. A perfect compliment to the House Special.