My head is full of whispers
which tomorrow will be silent.
Listen. The glass is breaking.
The trees are stumbling forward
into the night. Winds rush to meet them.
The moon is broken like a mirror,
its pieces flash now in the crown
of the tallest oak.
Adrienne Rich has compared the existence of women with the existence of trees in nature in the poem. When a woman feels trapped, she longs to get out of the constant chatter. When one is experiencing pain, there is a constant restlessness in the head. Peace is also accompanied by silence and calmness. People always look for serenity in life. But it isn't easy to obtain this state when one is in captivation.
Rich says that her head is full of whispers. These whispers could be that of her ancestors, who were also women in captivation. They could be voices asking her to avenge and establish a life of her own. She is restless, just like the trees. They could be voices of doubt and disbelief as to whether they can ever liberate themselves. But she says that she could finally be relieved by the next day of all the voices and chatter in her head. Tomorrow will be silent as the trees will all have managed to get out of their enclosed spaces by then. It is with conviction that Rich quotes this. She also engages with the readers and asks them to stop, pause and listen. She asks them to listen to the  change as they are arriving after a long time.
Rich also says that the glass is finally breaking. This means that the trees are finally growing bigger than their oppressors. This is very similar to women breaking the glass ceiling that stops them from growing big. Also, since they have been oppressed so far, they are not making a steady rise and movement, rather it is a slow one with them stumbling. But as soon as they get out, the wind rushes to meet them, making the leaves rustle. The moon appears as though it is broken as the tall trees cover it. It appears as if the moon is in pieces and is sitting at the top of the tall oak trees.
Moon appears spread on the trees
Meaning of difficult words:
WhispersSpeaking in a hushed tone
StumblingNot walking properly and falling
FlashTo appear only for a minute
CrownThe top layer of something
OakA tall sturdy tree
ChatterConstant speaking
CaptivationTo be held as a prisoner
ConvictionTo speak with confidence
SerenityCalm and peace
Glass ceilingDenotes the barrier that women cannot achieve higher positions
National Council of Educational Research and Training (2006). Beehive. The Trees - Adrienne Rich (pp. 99-101). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.