What is the importance of the poem written in The Night of the Iguana?

Nonno's poem is significant on several levels. First, the elderly poet has finally completed a new work. He dies, apparently content after doing so.

Second, Nonno has few lines in the play and largely functions as Hannah's charge. Caring for her grandfather as they travel gives her life some purpose. In another sense, however, he holds her back. Nonno seems to hear what the others say, so he is somewhat aware of Hannah's and Shannon's conversations.

In the latter regard, the poem's content is also significant. It is about observing in contrast to doing, hope versus despair, and about second chances. Everyone in the play is at the end of their rope in some regard. Shannon is a wreck of a man, Hannah has few options, and Nonno is at the end of his life. The poem's meaning largely parallels that of the play. Nonno is Hannah's rope, and his death frees her. Shannon is his own worst enemy, who needs a new lease on life; he literally gets tied up. While Hannah' compassion saves him, he in turns shows compassion to the iguana, which represents his second chance- the "second place to dwell... in the frightened heart."

The play ends with Jonathan Coffin, Hannah's elderly grandfather or "nonno", completing one last poem before he dies. The last two stanzas are: 

And still the ripe fruit and the branch
Observe the sky begin to blanch
Without a cry, without a prayer,
With no betrayal of despair.

Oh, Courage, could you not as well
Select a second  place to dwell,
Not only in that golden tree
But in the frightened heart of me?

At ninety-two years old, the poem is a breakthrough for Coffin, who has not been able to write for some time. In a way, it sums up his life, which has been haunted by fear.

What is the significance of the iguana in The Night of the Iguana?

Tennessee Williams includes the iguana as a live animal and makes it a symbol that stands for the human condition, especially in reference to specific characters who are limited or restrained in various ways.

The animal is a harmless creature that people have tied up to consume in the future. While all the characters must deal with particular limitations, Larry Shannon is especially held back by emotional problems, including loss of faith and the long-term effects of alcoholism. For much of the play, he seems to be at the mercy of those forces, much like the iguana is helpless to overcome or escape from its restraints. At one point, Maxine even ties him up to prevent him from destructive behavior. It seems he has not much farther to fall, and he strikes up an unlikely friendship with Hannah Jelkes, who is a companion to her grandfather, Jonathan “Nonno” Coffin.

The positions of Hannah and Nonno also show severe restraints. Nonno, once a famous poet, is now at the end of his career and—as shown later in the play—at the end of his life. Hannah has virtually no life of her own, as she dedicates herself to caring for and traveling with Nonno. Conversations with Hannah, who is presented much as a secular nun, inspire Shannon to reevaluate his options.

Ultimately, he unties the iguana and, in freeing the animal, also frees himself. Rather than trying to evade his personal demons, he achieves release by confronting them. Once he has announced his act of freeing the animal, it is revealed that Nonno has died. That event releases him from the frustrations caused by his declining powers but frees Hannah to pursue an independent life.

What does "iguana" symbolize in the title The Night of the Iguana?

The precise meaning of the iguana in Williams's play has never been established to everyone's satisfaction. So what follows is largely speculative but nonetheless based on certain lines of critical inquiry into the play and its symbols.

On one reading, the iguana represents freedom or, rather, the lack of it. The iguana is tied up for most of the play, ready to be eaten by some boys after it has become sufficiently plump and juicy. In that sense, it has no freedom at all. However, right at the end of the play, the iguana is given its freedom after it is cut loose by the defrocked priest Shannon.

That Shannon should be the one to free the iguana is instructive. Like the iguana, he himself has been robbed of freedom in that he has found himself tied down by society's morals and restrictions, not to mention those of the Episcopal Church to which he wishes to return.

In cutting loose the iguana at the end of the play, Shannon is symbolically freeing himself from the many demons that have tormented him for so long. He can now move on with his life, establishing a professional relationship with Maxine in the management of her hotel.