Is the word plantas the same in Brazilian and European Portuguese?

Yes

The only difference between "plantas" in Brazilian Portuguese and Continental Portuguese is pronunciation.

In Brazilian Portuguese, vowels are generally more open and articulated clearly, giving the word a more melodic and "syllable-timed" sound. The unstressed vowels are pronounced distinctly.

In Continental Portuguese, there is a strong tendency to reduce or "swallow" unstressed vowels. This results in a more "clipped" or "compressed" pronunciation, where the first "a" in "plantas" may sound much more closed or even nearly disappear to a Brazilian ear.

Brazilian Portuguese Examples:

1. Eu adoro cuidar das minhas plantas. (I love taking care of my plants.)
2. As plantas estão morrendo por causa do calor. (The plants are dying because of the heat.)
3. Você já regou as plantas hoje? (Have you watered the plants today?)
4. Eu comprei várias plantas novas para a sala. (I bought several new plants for the living room.)
5. As plantas precisam de muita luz solar. (The plants need a lot of sunlight.)

Continental Portuguese Examples:

1. Eu adoro cuidar das minhas plantas. (I love taking care of my plants.)
2. As plantas estão a morrer por causa do calor. (The plants are dying because of the heat.)
3. Já regaste as plantas hoje? (Have you watered the plants today?)
4. Comprei várias plantas novas para a sala. (I bought several new plants for the living room.)
5. As plantas precisam de muita luz solar. (The plants need a lot of sunlight.)