Thoroughbred owners and trainers who wish to make their late-blooming three-year-olds eligible to compete in the 2012 Triple Crown series of U.S. classic races have until Saturday, March 24, to add their horses to the roster of late nominations to the Kentucky Derbyat Churchill Downs, the Preakness Stakes at Pimlico, and the Belmont Stakes at Belmont Park.

A payment of $6,000 must accompany each nomination made during the late phase of Triple Crown nominations, which will close on Saturday at 11:59 p.m. (EDT). This year’s early nomination period, during which each nomination was accompanied by a $600 fee, closed on January 21 with 397 horses made eligible.

The 2012 Triple Crown series begins at Churchill Downs in Louisville on Saturday, May 5 with the 138th running of the $2-million Kentucky Derby. The second jewel of the Triple Crown is the 137th running of the $1-million Preakness Stakes, which will be run on Saturday, May 19, at Pimlico Race Course in Baltimore. The U.S. classics conclude with the 144th running of the Belmont Stakes on Saturday, June 9 at New York’s Belmont Park.

The total of 397 nominees in the early nomination phase was a 9.3% increase from 364 horses nominated for the series during the same period in 2011. The 2012 early total was the largest since 2009, when the early period yielded 412 nominees.

Last year’s last nomination period added 13 three-year-olds to 2011 Triple Crown nominations and raised the overall total to 377. Among last year’s late nominations was George and Lori Hall’s Ruler On Ice, who would go on to win the Belmont Stakes.

All nominations made by traditional mail during the late nomination phase must be postmarked on or before March 24. Triple Crown nominations can also be made online at www.TheTripleCrown.com, or via telephone with a designated representative from one of the three Triple Crown host tracks. Online and telephone nominations must be made prior to the 11:59 p.m. deadline on Saturday.