Ako bude dovoljno vode, ruža će brzo narasti.

Croatian has two important present-type forms of biti:

• je = the normal present form, used for present-time statements
• bude = a special budem-type form, often used when a clause refers to the future, especially after words like ako meaning if

So:

• Ako je dovoljno vode = If there is enough water right now
• Ako bude dovoljno vode = If there is enough water at some future time

In this sentence, the condition is about the future, so bude is the natural choice.

In standard Croatian, after ako for a real future condition, you normally use bude, not će biti.

So the usual pattern is:

• Ako bude ... , ... će ...

This is similar to English in one important way: English also avoids will in many if-clauses.

• English: If there is enough water, the rose will grow quickly
• Croatian: Ako bude dovoljno vode, ruža će brzo narasti

So the future marking appears mainly in the main clause, while the if-clause uses bude.

Because dovoljno meaning enough normally requires the genitive.

So:

• dovoljno vode = enough water
• not dovoljno voda

This is very common in Croatian with quantity words and similar expressions, for example:

• puno vode = a lot of water
• malo vode = a little water
• dosta vode = enough / quite a lot of water

So vode is genitive singular of voda.

Ruža is in the nominative singular because it is the subject of the sentence.

It is the thing doing the growing:

• ruža = the rose

If you ask what will grow quickly?, the answer is ruža. That is why nominative is used.

This is the normal way to form future I in Croatian:

• će
  • infinitive

So:

• narasti = infinitive, to grow
• će narasti = will grow

With a full verb, Croatian often uses this pattern in main clauses talking about the future.

In this sentence:

• ruža će brzo narasti = the rose will grow quickly

This is a question of aspect and also meaning nuance.

• rasti = to grow, focusing on the ongoing process
• narasti = to grow to a larger size / to grow up to a certain point, focusing more on the result

In this sentence, narasti fits well because the idea is that, if the condition is met, the rose will successfully grow bigger.

Very roughly:

• Ruža raste. = The rose is growing.
• Ruža će narasti. = The rose will grow / will grow big.

So narasti sounds more goal-oriented or result-oriented.

Because će is a clitic. In Croatian, clitics usually come in the second position of the clause.

So in:

• Ruža će brzo narasti

the first main element is ruža, and the clitic će comes right after it.

This is very normal Croatian word order.

English speakers often expect something like will the rose grow, with the future marker before the main verb phrase, but Croatian clitics follow their own placement rules.

Yes, Croatian word order is fairly flexible, although some versions sound more neutral than others.

The most neutral version here is:

• Ruža će brzo narasti.

But you may also hear or see:

• Ruža će narasti brzo.
• Brzo će narasti ruža.
• Ako bude dovoljno vode, brzo će narasti ruža.

These versions can sound more marked, more literary, or more focused on a particular word.

So the original sentence is a very natural, standard order:

• condition first
• then subject
• then clitic će
• then adverb brzo
• then infinitive narasti

No. It means enough water, without stating an exact quantity.

That is the same basic idea as in English:

• enough water

It simply means the amount of water is sufficient for the rose to grow quickly.

So the phrase is indefinite and general, not exact or measured.