The Grass Crown or Blockade Crown (Latin: corona graminea or corona obsidionalis) was the highest and rarest of all military decorations in the Roman Republic and early Roman empire. It was presented only to a general, commander, or officer whose actions saved the legion or the entire army. One example of actions leading to awarding of a grass crown would be a general who broke the blockade around a beleaguered Roman army. The crown was made from plant materials taken from the battlefield, including grasses, flowers, and various cereals such as wheat; it was presented to the general by the army he had saved.
But as for the crown of grass, it was never conferred except at a crisis of extreme desperation, never voted except by the acclamation of the whole army, and never to any one but to him who had been its preserver. Other crowns were awarded by the generals to the soldiers, this alone by the soldiers, and to the general. This crown is known also as the "obsidional" crown, from the circumstance of a beleaguered army being delivered, and so preserved from fearful disaster. If we are to regard as a glorious and a hallowed reward the civic crown, presented for preserving the life of a single citizen, and him, perhaps, of the very humblest rank, what, pray, ought to be thought of a whole army being saved, and indebted for its preservation to the valour of a single individual?
Pliny also lists the persons who by their deeds won the grass crown: