ookiku naru ni tsurete, uekae to sentei ga hitsuyou ni naru.

As it gets bigger, repotting and pruning become necessary.

Breakdown of ookiku naru ni tsurete, uekae to sentei ga hitsuyou ni naru.

• 大おおきい: big
• と: noun-connector particle
• が: subject particle
• なる: to become

Questions & Answers about ookiku naru ni tsurete, uekae to sentei ga hitsuyou ni naru.

Why is it 大きくなる and not 大きいなる?

Because 大きい is an い-adjective, and when an い-adjective is used before なる to mean become ..., it changes to its -く form.

• 大きい = big
• 大きくなる = to become big / to grow bigger

This is a very common pattern:

• 暑い → 暑くなる = become hot
• 早い → 早くなる = become early / become fast
• 大きい → 大きくなる = become big

So 大きいなる is not correct Japanese.

What does 〜につれて mean here?

〜につれて means as ..., in proportion as ..., or along with ....

In this sentence:

• 大きくなるにつれて = as it gets bigger
• as it grows, ...

This pattern is used when one change happens gradually, and another change happens along with it.

A simple way to think of it:

• X につれて Y = as X changes, Y also changes

Examples:

• 年を取るにつれて、記憶力が落ちる。
  As one gets older, memory declines.
• 気温が上がるにつれて、虫が増える。
  As the temperature rises, insects increase.

So here, as the plant or tree gets bigger, repotting and pruning become necessary.