Palmeras means 'palm trees'. While seemingly simple, this word is central to the song's core metaphor and creates a vivid, evocative image.
Alejandro Sanz uses "palmeras" to represent an attempt to transform his world to match his lover's, singing, "Pero por más palmeras que plantemo' en el jardín / Esto jamás será La Habana / Yo siempre seré Madrid." It beautifully symbolizes the futility of trying to change one's fundamental identity or origin to fit another's, making it a memorable and poignant choice.
Alejandro Sanz builds this whole song around one stubborn image: no matter how many palm trees you plant in a Madrid garden, it never turns into Havana. He says it outright — "Pero por más palmeras que plantemo' en el jardín" ("But however many palm trees we plant in the garden"), "esto jamás será La Habana" ("this will never be Havana"), "yo siempre seré Madrid" ("I will always be Madrid"). It's a breakup song where the geography does the talking: she's gone, and no amount of trying can make his own city into hers.
The verses stack up small, specific hurts instead of general sadness. He asks "¿Cómo es posible que me pises?" ("How is it possible that you step on me?") right after admitting she's the one who taught him to dance, and later "¿Por qué no me hablaste de los grises?" ("Why didn't you tell me about the gray days?") after she taught him to paint. Havana keeps showing up through Varadero, a real Cuban beach town he says she left behind in his soul, and Madrid answers back through the Cibeles fountain, which "me preguntó por ti" ("asked me about you") — even the city seems to miss her. By the last chorus he isn't fighting the comparison anymore. He's just repeating it, quieter each time.