Tulip Courtesy of Benjamin Swett hide caption

itoggle caption Courtesy of Benjamin Swett

American farms like this iceberg lettuce field owned by Duda Farm Fresh Foods outside Salinas, Calif., are facing a dwindling supply of farmworkers from rural Mexico. Kirk Siegler hide caption

itoggle caption Kirk Siegler

President Obama during his news conference Tuesday at the White House. Larry Downing /Reuters /Landov hide caption

itoggle caption Larry Downing /Reuters /Landov