Za pažljivo zalijevanje koristite raspršivač; kasnije dodajte gnojivo i orežite biljke.

Here za means for in the sense of purpose:

Za pažljivo zalijevanje = For careful watering

In this use, za takes the accusative case.

So:

• za
  • pažljivo zalijevanje

Both words happen to look the same as their dictionary forms because:

• zalijevanje is a neuter singular noun
• neuter singular nominative and accusative are the same
• pažljivo agrees with it, and its neuter singular nominative/accusative form is also the same

So even though the case is accusative, you do not see a visible ending change here.

In this sentence, pažljivo is an adjective, not an adverb.

It modifies zalijevanje:

• pažljivo zalijevanje = careful watering

This can be confusing because pažljivo is also the usual adverb form meaning carefully.

Compare:

• Za pažljivo zalijevanje koristite raspršivač.
  Here pažljivo describes the noun zalijevanje.

• Pažljivo zalijevajte biljke.
  Here pažljivo describes the verb zalijevajte.

So the form is the same, but the grammar role is different.

Zalijevanje is a verbal noun. It means watering.

It comes from the verb:

• zalijevati / zaliti = to water

Croatian very often uses verbal nouns like this in instructions and formal writing.

So:

• zalijevanje = watering
• orezivanje = pruning
• gnojenje = fertilizing

This is similar to English watering as a noun, as in for careful watering.

Koristite can be either:

• you use / you are using (present tense, plural or formal singular)
• use! (imperative, plural or formal singular)

In this sentence, because it is giving instructions, it is understood as a command/instruction:

• koristite raspršivač = use a sprayer / use the sprayer

This form is used for:

• more than one person
• one person addressed formally/politely

If you were speaking to one person informally, you would say:

• koristi

Raspršivač means something like:

• sprayer
• spray bottle
• mister
• sometimes sprinkling device

The exact English translation depends on context.

In a plant-care sentence like this, it most likely means a spray bottle or plant mister used for gentle watering.

It comes from the idea of dispersing/spraying liquid into fine droplets.

A learner may also see other related words in similar contexts, such as:

• prskalica = sprayer / spray bottle
• raspršiti = to spray / disperse

Because Croatian does not have articles.

So:

• raspršivač can mean a sprayer or the sprayer
• gnojivo can mean fertilizer or the fertilizer
• biljke can mean plants or the plants

Croatian usually leaves definiteness to:

• context
• word order
• the situation
• sometimes demonstratives like taj, ovaj, onaj

So English articles are simply not translated word-for-word.

Kasnije means later or later on.

In this sentence:

• kasnije dodajte gnojivo = later, add fertilizer

Yes, its position is somewhat flexible. You could also say:

• Kasnije dodajte gnojivo i orežite biljke.

That version is probably the most neutral in everyday writing.

The original placement is also fine. Croatian word order is more flexible than English, especially with adverbs like kasnije.

They are imperative forms, used to give instructions:

• dodajte = add
• orežite = prune / trim

This is very common in recipes, manuals, and gardening instructions.

These forms are:

• 2nd person plural imperative
• also used as formal singular imperative

So the sentence is speaking either to:

• a group of people, or
• one person politely

Because dodajete and režete are normally present tense, not commands.

Compare:

• dodajete = you add / you are adding
• režete = you cut / you are cutting

But in instructions you usually want:

• dodajte = add!
• orežite = prune!

Also, orežite is better than režite here because:

• rezati = to cut in general
• orezati = to prune, trim back, cut as part of plant care

So orežite biljke sounds much more natural in a gardening context than režite biljke.

It is in the accusative singular, because it is the direct object of dodajte.

However, gnojivo is a neuter singular noun, and for many neuter nouns:

• nominative singular = accusative singular

So:

• dictionary form: gnojivo
• accusative form: gnojivo

No visible change appears, even though the grammatical case has changed.

Biljke is in the accusative plural, because it is the direct object of orežite:

• orežite biljke = prune the plants

The noun biljka is feminine. Its forms are:

• nominative singular: biljka
• accusative singular: biljku
• nominative plural: biljke
• accusative plural: biljke

So here biljke looks the same as the nominative plural, but in the sentence it is accusative plural.

This is normal for many feminine nouns in Croatian.

These verbs are related, but not identical:

• rezati = to cut in a general sense
• orezati = to prune, especially plants, branches, shrubs
• podrezati = to trim, cut back, sometimes slightly or neatly

So in gardening:

• orežite biljke is the most natural general instruction for prune the plants
• režite biljke sounds too general, almost just cut the plants
• podrežite biljke suggests trim them back

So the choice of orežite is specific and appropriate.

The semicolon separates two closely connected instruction stages:

1. Za pažljivo zalijevanje koristite raspršivač
2. kasnije dodajte gnojivo i orežite biljke

A semicolon is useful when:

• the two parts are strongly related
• each part is a complete instruction idea
• the writer wants a clearer pause than a comma gives

A full stop would also be possible:

• Za pažljivo zalijevanje koristite raspršivač. Kasnije dodajte gnojivo i orežite biljke.

That would sound completely natural too.

So this is mainly a punctuation/style choice, not a major grammar issue.