W miarę jak sadzonka się ukorzenia, rośnie nowy pęd.

W miarę jak means something like as, as... progresses, or in proportion as.

It introduces a gradual relationship between two processes:

• W miarę jak sadzonka się ukorzenia... = As the cutting/seedling takes root...
• ...rośnie nowy pęd. = ...a new shoot grows.

So this phrase is useful when one thing happens progressively alongside another.

Examples:

• W miarę jak robi się ciemno, robi się chłodniej.
  As it gets dark, it gets cooler.
• W miarę jak dziecko rośnie, zmieniają się jego potrzeby.
  As the child grows, its needs change.

The verb here is ukorzeniać się / ukorzenić się, which means to take root or to become rooted.

The się is part of the verb. In many Polish verbs, się does not always mean a literal reflexive itself. Sometimes it helps form a verb that describes a process happening to the subject.

So:

• ukorzeniać can mean to root something
• ukorzeniać się means to take root

Compare:

• Ogrodnik ukorzenia sadzonkę.
  The gardener is rooting the cutting.
• Sadzonka się ukorzenia.
  The cutting is taking root.

So in this sentence, się is not optional.

Both can be related to rooting, but they are not always used in exactly the same way.

• ukorzeniać się / ukorzenić się = to take root
• zakorzeniać się / zakorzenić się = to become rooted, often with a sense of becoming established

In gardening contexts, ukorzeniać się is very natural for a cutting or young plant beginning to develop roots.

In broader or figurative use, zakorzenić się is often common too:

• Ten zwyczaj zakorzenił się w społeczeństwie.
  This custom became rooted in society.

In your sentence, ukorzenia się focuses nicely on the biological process of developing roots.

Sadzonka usually means a seedling, young plant, or often a cutting intended for planting.

The exact English translation depends on context:

• in gardening, it can be a seedling
• if it is a piece of a plant being rooted, cutting may be the best translation

Since the sentence talks about taking root and then producing a new shoot, cutting or young plant may fit especially well.

Grammatically, sadzonka is:

• feminine singular
• nominative here, because it is the subject of się ukorzenia

Because the subject of the second clause is nowy pęd (a new shoot), which is singular.

So:

• rośnie nowy pęd = a new shoot grows
• singular subject → singular verb

If it were plural, you would say:

• rosną nowe pędy = new shoots grow

Even though sadzonka appears earlier in the sentence, it is the subject only of the first clause:

• sadzonka się ukorzenia
• nowy pęd rośnie

Both are possible.

• Rośnie nowy pęd.
• Nowy pęd rośnie.

Polish word order is more flexible than English, because grammatical endings show the roles of words more clearly.

In this sentence, rośnie nowy pęd sounds natural and slightly more descriptive or narrative, almost like there is a new shoot growing.

Compare the feel:

• Rośnie nowy pęd.
  Focuses a bit more on the process/result: a new shoot is growing.
• Nowy pęd rośnie.
  Focuses more directly on the new shoot as the topic.

So the original word order is normal and stylistically natural.

It is in the nominative singular.

Why? Because nowy pęd is the subject of rośnie.

You can tell from the adjective and noun forms:

• nowy = nominative masculine singular
• pęd = nominative masculine singular

If it were an object in another case, the form would likely change. For example:

• Widzę nowy pęd.
  Here nowy pęd is accusative, but for this masculine inanimate noun, the form happens to look the same as nominative.

In your sentence, though, its role is clearly that of the subject: a new shoot grows.

The comma separates two clauses:

• W miarę jak sadzonka się ukorzenia
• rośnie nowy pęd

The first clause is subordinate and introduced by w miarę jak, so a comma is required before the main clause.

This is very common in Polish when a sentence begins with a subordinating expression like:

• gdy
• kiedy
• ponieważ
• jeśli
• w miarę jak

So the punctuation here is standard and expected.

Because Polish uses the present tense to describe ongoing, general, or repeated processes, just like English often does.

Here both actions are happening as processes:

• sadzonka się ukorzenia = the cutting is taking root
• rośnie nowy pęd = a new shoot is growing

These are imperfective present forms, which are perfect for describing something in progress.

This is one of the normal uses of the Polish present tense:

• Dziecko rośnie. = The child is growing.
• Roślina kwitnie. = The plant is flowering.

Here it is imperfective.

The full imperfective infinitive is ukorzeniać się.
Its present-tense form is ukorzenia się.

That makes sense because the sentence describes an ongoing process, not a completed result.

Compare:

• ukorzeniać się = imperfective, to be taking root / to take root as a process
• ukorzenić się = perfective, to take root successfully / become rooted as a completed event

Examples:

• Sadzonka się ukorzenia.
  The cutting is taking root.
• Sadzonka się ukorzeniła.
  The cutting took root / has rooted.

You could, but the meaning would shift slightly.

• w miarę jak emphasizes a gradual parallel development
  = as, as... progressively
• gdy / kiedy usually mean when or while

So:

• W miarę jak sadzonka się ukorzenia, rośnie nowy pęd.
  This highlights that the new shoot grows progressively as rooting develops.

If you said:

• Gdy sadzonka się ukorzenia, rośnie nowy pęd.

that sounds more like when/while the cutting is taking root, a new shoot grows, which is understandable, but it does not emphasize the gradual relationship as clearly.

So w miarę jak is the best choice here.

It can work as either, depending on context, but by itself it sounds very natural as a general biological or gardening statement.

Polish present tense often expresses general truths or typical processes:

• Woda wrze w temperaturze 100 stopni.
• Rośliny potrzebują światła.

In your sentence, the present tense and the structure make it sound like an explanation of how plants develop:

As the cutting takes root, a new shoot grows.

If you wanted to describe one specific past event, Polish would normally use past-tense forms instead.

Pęd in a plant context means a shoot or stem growth, especially a new growing part of the plant.

It is a common botanical/gardening word.

Related plant words:

• korzeń = root
• łodyga = stem
• liść = leaf
• pąk = bud
• pęd = shoot

So nowy pęd is a new shoot.

In other contexts, pęd can have other meanings, but in this sentence the plant meaning is clearly intended.