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

Yes

The word "plantei" is identical in meaning, grammar, and spelling in both Brazilian and European Portuguese. It is the first-person singular form of the verb plantar in the pretérito perfeito do indicativo (past tense). The only difference is pronunciation:

• In Brazilian Portuguese, the vowels are generally more open and clearly articulated.
• In Continental Portuguese, the vowels are more "reduced" or closed, meaning the unstressed "e" may sound much shorter or nearly silent to an untrained ear.

Brazilian Portuguese Examples

1. Eu plantei algumas flores no jardim hoje de manhã. (I planted some flowers in the garden this morning.)
2. Plantei uma semente de tomate no vaso. (I planted a tomato seed in the pot.)
3. Ontem eu plantei uma árvore frutífera no quintal. (Yesterday I planted a fruit tree in the backyard.)
4. Eu plantei o que aprendi no curso de jardinagem. (I planted [implemented] what I learned in the gardening course.)
5. Eu plantei as sementes e estou esperando elas crescerem. (I planted the seeds and I am waiting for them to grow.)

European Portuguese Examples

1. Plantei umas flores no jardim hoje de manhã. (I planted some flowers in the garden this morning.)
2. Plantei uma semente de tomate no vaso. (I planted a tomato seed in the pot.)
3. Ontem plantei uma árvore de fruto no quintal. (Yesterday I planted a fruit tree in the backyard.)
4. Plantei o que aprendi no curso de jardinagem. (I planted [implemented] what I learned in the gardening course.)
5. Plantei as sementes e estou à espera que cresçam. (I planted the seeds and I am waiting for them to grow.)