Etter hvert som stiklingen vokser, blir røttene lengre.

Etter hvert som means something like as, as time goes on, or gradually as.

In this sentence, it shows that the two things happen progressively at the same time:

• Etter hvert som stiklingen vokser = As the cutting grows
• blir røttene lengre = the roots become longer

So etter hvert som is a good choice when one change happens little by little while another process is also developing.

Stiklingen is the definite singular form of stikling.

In Norwegian, definiteness is usually shown by adding an ending to the noun:

• en stikling = a cutting
• stiklingen = the cutting

Here, the sentence is talking about the specific cutting being discussed, so stiklingen is used.

Røttene is the definite plural form of rot (root).

The forms are:

• en rot = a root
• røtter = roots
• røttene = the roots

So røttene means the roots, not just roots in general. Norwegian often uses the definite form where English might also use the, but Norwegian expresses that definiteness with the ending -ene.

Because blir means becomes / gets, while er means is / are.

Compare:

• Røttene er lange = The roots are long
• Røttene blir lengre = The roots are becoming longer / getting longer

This sentence describes a change, so blir is the natural choice.

Lengre is the comparative form of lang (long).

The pattern is:

• lang = long
• lengre = longer
• lengst = longest

So:

• røttene blir lengre = the roots become longer

This is like English long → longer.

This is a very common question.

In modern Norwegian, lengre and lenger can both appear as comparative forms related to lang. Very roughly:

• lengre is often used more clearly as longer
• lenger is very common in expressions about time, distance, or no longer

Examples:

• en lengre vei = a longer road
• Jeg kan ikke vente lenger = I can’t wait any longer
• Han bor lenger unna = He lives farther away

In your sentence, lengre fits well because it describes the physical length of the roots.

This is because of Norwegian V2 word order.

The sentence begins with a subordinate clause:

• Etter hvert som stiklingen vokser

After that comes the main clause. In Norwegian main clauses, the finite verb normally has to be in the second position. Since the sentence already starts with that fronted clause, the verb comes before the subject:

• Etter hvert som stiklingen vokser, blir røttene lengre.

If you wrote the main clause by itself, the normal order would be:

• Røttene blir lengre.

But after the fronted clause, Norwegian switches to:

• ..., blir røttene lengre.

This is very typical Norwegian word order.

Because Norwegian often uses the present tense to describe:

• general truths
• ongoing processes
• things that happen regularly or naturally

Here, the sentence describes a process:

• stiklingen vokser = the cutting grows / is growing
• røttene blir lengre = the roots become / are becoming longer

English sometimes prefers is growing or are getting longer, but Norwegian very naturally uses the simple present here.

Not with exactly the same meaning.

• Når stiklingen vokser, blir røttene lengre sounds more like when the cutting grows, the roots get longer
• Etter hvert som stiklingen vokser, blir røttene lengre emphasizes a gradual development over time

So etter hvert som is better if you want the idea of as it grows, step by step, the roots get longer too.

Yes, it is standard to put a comma after the initial subordinate clause.

So:

• Etter hvert som stiklingen vokser, blir røttene lengre.

The comma marks the end of the first clause and makes the structure easier to read.

Yes. That is a very close, literal translation:

• røttene = the roots
• blir = become / get
• lengre = longer

In natural English, you might also say:

• the roots get longer
• the roots grow longer

All of those match the Norwegian sentence well.

A useful way to see it is:

Etter hvert som + clause, main clause

So here:

• Etter hvert som stiklingen vokser = subordinate clause
• blir røttene lengre = main clause

Word-for-word structure:

• Etter hvert som = as / as time goes on
• stiklingen = the cutting
• vokser = grows
• blir = becomes / gets
• røttene = the roots
• lengre = longer

That makes it easier to build similar sentences of your own.