Díky dešťové vodě můžeme zalévat sazenice.

Here díky is a preposition meaning thanks to or due to.

A useful nuance:

• díky often suggests a helpful or positive cause
• that fits well here, because rainwater is something useful

So Czech uses díky naturally in this sentence.

Because díky requires the dative case.

The basic form is:

• dešťová voda = rainwater

But after díky, both words must change into dative singular:

• dešťová → dešťové
• voda → vodě

So:

• díky dešťové vodě

Díky takes the dative.

Some examples:

• díky kamarádovi
• díky pomoci
• díky dešťové vodě

So if you see díky, it is a good idea to expect a dative form after it.

Because dešťovou vodou is instrumental, not dative.

That form would be correct in a different sentence, for example:

• Zaléváme sazenice dešťovou vodou.
  • We water the seedlings with rainwater.

But in your sentence, the structure is:

• díky + dative

So it must be:

• díky dešťové vodě

Můžeme is the 1st person plural present tense of moci.

So it means:

• we can
• we are able to

It is followed by an infinitive:

• můžeme zalévat

This is the normal Czech pattern for modal verbs:

• můžu dělat
• můžeš jít
• můžeme zalévat

This is about aspect.

• zalévat = imperfective
• zalít = perfective

Here zalévat is natural because the sentence talks about a general ability or repeated action: rainwater lets us water seedlings in general.

Compare:

• můžeme zalévat sazenice = we can water seedlings / we are able to water seedlings
• můžeme zalít sazenice = we can water the seedlings once / complete that action

So zalévat fits the broader, habitual meaning better.

Here it is plural: seedlings.

Why this can be confusing:

• sazenice can also be the singular nominative form
• but in this sentence it is the accusative plural form

After zalévat, we expect a direct object, and here that object is plural:

• zalévat sazenice = to water seedlings

If it were singular, you would normally get:

• zalévat sazenici = to water a seedling

Because Czech has no articles.

English needs words like:

• a
• an
• the

Czech usually does not use anything equivalent. The exact meaning is understood from context.

So sazenice could mean:

• seedlings
• the seedlings
• some seedlings

depending on the situation.

Yes. Czech word order is relatively flexible.

This version:

• Díky dešťové vodě můžeme zalévat sazenice.

puts emphasis first on the reason or source of possibility: thanks to rainwater.

Other possible orders include:

• Můžeme díky dešťové vodě zalévat sazenice.
• Sazenice můžeme zalévat díky dešťové vodě.

These are still grammatical, but the focus shifts slightly. Czech often moves words around to show emphasis rather than changing the basic meaning.

A few helpful points:

• Czech stress is usually on the first syllable
• ů and é are long vowels
• ž sounds like the sound in measure

Rough pronunciation:

• dešťové ≈ DEŠ-ťo-vé
• můžeme ≈ MŮ-že-me

The tricky part is šť in dešťové:

• š is like sh
• ť is a soft t sound

You do not need to make it perfect immediately; just aim for a soft cluster after deš-.

Because these adjectives mean different things.

• dešťový = related to rain, made from rain, rain-
• deštivý = rainy

So:

• dešťová voda = rainwater
• deštivé počasí = rainy weather

That is why dešťové vodě is the correct form here.

Yes, but it would not mean exactly the same thing.

• díky dešti = thanks to the rain
• díky dešťové vodě = thanks to rainwater

The original sentence specifically focuses on the water collected from rain, not just the fact that it rained.

So both are possible Czech, but they express slightly different ideas.