K přesazování potřebujeme nový substrát.

Here k means something like for or for the purpose of.

So:

• K přesazování = for transplanting / for repotting

In Czech, k normally takes the dative case. In this sentence, it introduces the activity that something is needed for.

A very natural English translation is:

• For repotting, we need new substrate.
• or more naturally: We need new potting mix for repotting.

Czech often uses k + dative in this kind of practical, instructional style.

Přesazování is a verbal noun. It means transplanting / repotting as an activity or process.

Compare:

• přesazovat = to transplant / to repot (verb)
• přesazování = transplanting / repotting (noun)

So the sentence is built around a noun phrase:

• K přesazování = for repotting

This is very common in Czech, especially in instructions, guides, and explanations.

After k, Czech requires the dative case.

The word přesazování is a neuter verbal noun, and in this pattern its form is the same in both:

• nominative: přesazování
• dative: k přesazování

So even though the ending does not change, it is still dative because it follows k.

This can feel strange to English speakers, because English does not show case this way, but in Czech the preposition controls the case.

In gardening context, přesazování can mean both, depending on what is being moved:

• moving a plant into another pot = repotting
• moving a plant to a different place/soil = transplanting

Because the sentence also mentions substrát, this often suggests gardening or houseplants, so repotting is probably the most natural interpretation in many situations.

Potřebujeme is the 1st person plural present tense of potřebovat (to need).

So:

• potřebuji = I need
• potřebuješ = you need
• potřebujeme = we need

That means:

• K přesazování potřebujeme nový substrát.
• For repotting, we need new substrate/potting mix.

Czech often uses we in instructional or explanatory contexts, similar to English we need in recipes, manuals, or tutorials.

Because nový substrát is the direct object of potřebujeme (we need), so it is in the accusative case.

The noun substrát is:

• masculine inanimate
• singular

For many masculine inanimate nouns, the accusative singular looks the same as the nominative singular.

So:

• nominative: nový substrát
• accusative: nový substrát

That is why the form does not visibly change here.

It is related, but in everyday Czech gardening language substrát often means potting mix, growing medium, or a prepared soil mix for plants.

So although the direct cognate is substrate, a more natural English translation in this context is often:

• potting soil
• potting mix
• growing medium

If this is about houseplants, new potting mix is probably the most natural everyday translation.

Because Czech has no articles.

English says:

• a new substrate
• the new substrate

Czech simply says:

• nový substrát

Context tells you whether it means a, the, or sometimes just a general noun.

In this sentence, English usually needs a:

• We need a new substrate / new potting mix for repotting.

Yes. Czech word order is more flexible than English.

For example, these are both natural:

• K přesazování potřebujeme nový substrát.
• Potřebujeme nový substrát k přesazování.

Both mean basically the same thing. The difference is mainly focus or style.

• K přesazování... puts early emphasis on the activity: as for repotting / for repotting
• Potřebujeme nový substrát... starts with the main statement: we need new potting mix

The original sentence sounds quite natural in explanatory or instructional language.

The sentence follows a very normal Czech pattern:

• [purpose/topic] + [verb] + [object]

So:

• K přesazování = for repotting
• potřebujeme = we need
• nový substrát = new potting mix

Czech often puts contextual information first, especially in instructional sentences. English can do this too, but Czech does it more freely.

Yes. It is connected to the verb pair:

• přesadit = perfective, to repot/transplant once, to complete the action
• přesazovat = imperfective, to be repotting/transplanting, to do it repeatedly or as a process

The noun přesazování is based on the imperfective idea of the activity as a process:

• přesazování = repotting / transplanting

That makes sense here, because the sentence is talking about what is needed for the activity, not about one completed action.

Yes, very much.

Czech instructions and how-to texts often use:

• we forms like potřebujeme = we need
• purpose phrases like k přesazování = for repotting

This gives the sentence a practical, helpful tone, similar to English instructions like:

• For repotting, we need fresh potting mix.
• To repot the plant, we need new potting soil.

So the sentence sounds very natural in a gardening guide or tutorial.