This is not a poem, but here's a sweet passage from the Little Prince:

"You are beautiful, but you are empty," he went on. "One could not die
for you. To be sure, an ordinary passerby would think that my rose
looked just like you--the rose that belongs to me. But in herself
alone she is more important than all the hundreds of you other roses:
because it is she that I have watered; because it is she that I have
put under the glass globe; because it is for her that I have killed
the caterpillars (except the two or three we saved to become
butterflies); because it is she that I have listened to, when she
grumbled, or boasted, or even sometimes when she said nothing. Because
she is my rose."