Background: Walter "Walt" Whitman (; May 31, 1819 - March 26, 1892) was an American poet, essayist, and journalist. A humanist, he was a part of the transition between transcendentalism and realism, incorporating both views in his works. Whitman is among the most influential poets in the American canon, often called the father of free verse.
Context: Whitman claimed that after years of competing for "the usual rewards", he determined to become a poet. He first experimented with a variety of popular literary genres which appealed to the cultural tastes of the period. As early as 1850, he began writing what would become Leaves of Grass, a collection of poetry which he would continue editing and revising until his death. Whitman intended to write a distinctly American epic and used free verse with a cadence based on the Bible. At the end of June 1855, Whitman surprised his brothers with the already-printed first edition of Leaves of Grass. George "didn't think it worth reading".  Whitman paid for the publication of the first edition of Leaves of Grass himself and had it printed at a local print shop during their breaks from commercial jobs. A total of 795 copies were printed. No name is given as author; instead, facing the title page was an engraved portrait done by Samuel Hollyer, but 500 lines into the body of the text he calls himself "Walt Whitman, an American, one of the roughs, a kosmos, disorderly, fleshly, and sensual, no sentimentalist, no stander above men or women or apart from them, no more modest than immodest". The inaugural volume of poetry was preceded by a prose preface of 827 lines. The succeeding untitled twelve poems totaled 2315 lines--1336 lines belonging to the first untitled poem, later called "Song of Myself". The book received its strongest praise from Ralph Waldo Emerson, who wrote a flattering five-page letter to Whitman and spoke highly of the book to friends. The first edition of Leaves of Grass was widely distributed and stirred up significant interest, in part due to Emerson's approval, but was occasionally criticized for the seemingly "obscene" nature of the poetry. Geologist John Peter Lesley wrote to Emerson, calling the book "trashy, profane & obscene" and the author "a pretentious ass". On July 11, 1855, a few days after Leaves of Grass was published, Whitman's father died at the age of 65.  In the months following the first edition of Leaves of Grass, critical responses began focusing more on the potentially offensive sexual themes. Though the second edition was already printed and bound, the publisher almost did not release it. In the end, the edition went to retail, with 20 additional poems, in August 1856. Leaves of Grass was revised and re-released in 1860 again in 1867, and several more times throughout the remainder of Whitman's life. Several well-known writers admired the work enough to visit Whitman, including Amos Bronson Alcott and Henry David Thoreau.  During the first publications of Leaves of Grass, Whitman had financial difficulties and was forced to work as a journalist again, specifically with Brooklyn's Daily Times starting in May 1857. As an editor, he oversaw the paper's contents, contributed book reviews, and wrote editorials. He left the job in 1859, though it is unclear whether he was fired or chose to leave. Whitman, who typically kept detailed notebooks and journals, left very little information about himself in the late 1850s.
Question: How long or how many poetry are there in leaves of grass?

Answer:
Leaves of Grass was revised and re-released in 1860 again in 1867, and several more times throughout the remainder of Whitman's life.