Með garðáhöldunum setjum við áburð kringum graskerin, steinseljuna og graslaukinn.

Because með normally takes the dative case in Icelandic.

So:

• garðáhöld = garden tools
• garðáhöldunum = the garden tools in the dative plural

The ending -unum is the typical dative plural definite ending here.

In this sentence, með garðáhöldunum means with the garden tools or more naturally using the garden tools.

It breaks down like this:

• garð- = garden
• áhöld = tools, implements
• -unum = the dative plural definite ending, roughly the

So the whole word means with the garden tools.

A useful comparison:

• garðáhöld = garden tools
• garðáhöldin = the garden tools
• garðáhöldum = with garden tools
• garðáhöldunum = with the garden tools

This is because Icelandic follows a verb-second pattern in main clauses.

If something other than the subject comes first, the finite verb usually comes next, and the subject comes after it.

So:

• Við setjum áburð... = We put/apply fertilizer...
• Með garðáhöldunum setjum við áburð... = With the garden tools, we put/apply fertilizer...

The first part, Með garðáhöldunum, has been moved to the front for focus or style, so setjum has to stay in second position.

Setjum is the 1st person plural present form of setja.

So it means:

• we put
• we place
• in this context, more naturally we apply

In Icelandic, the present tense can often cover both English simple present and present progressive, depending on context. So setjum við áburð can be understood as we put/apply fertilizer or we are putting/applying fertilizer.

Because áburð is the accusative singular form of áburður.

The noun áburður is masculine:

• nominative: áburður
• accusative: áburð

Since it is the direct object of setjum, it appears in the accusative:

• setja áburð = to put/apply fertilizer

Also, there is no definite article here because fertilizer is being used as a mass noun, not as the fertilizer.

Kringum is a preposition meaning around. It takes the accusative case.

That is why the nouns after it are in accusative forms:

• graskerin
• steinseljuna
• graslaukinn

So:

• kringum graskerin = around the pumpkins
• kringum steinseljuna = around the parsley
• kringum graslaukinn = around the chives / the chive plant

You may also see í kringum in Icelandic, which can also mean around, but here the simple preposition kringum is used.

Because they are different nouns with different genders and numbers, and Icelandic endings change accordingly.

Here is what each one is:

• graskerin = the pumpkins
  
  • from grasker
  • neuter plural definite
• steinseljuna = the parsley
  
  • from steinselja
  • feminine singular definite accusative
• graslaukinn = the chives / the chive plant
  
  • from graslaukur
  • masculine singular definite accusative

So the different endings are not random—they show gender, number, case, and definiteness.

That reflects how the speaker is choosing to talk about those plants.

• graskerin is clearly plural: multiple pumpkins.
• steinseljuna is singular definite: the parsley.
• graslaukinn is also singular definite.

In Icelandic, plant and herb names are often used in the singular where English may sometimes prefer a mass noun or even a plural-looking translation. So graslaukur can refer to chives as a plant/crop, not necessarily just one isolated blade.

In other words, the grammar follows Icelandic noun usage, not necessarily the most literal English pattern.

These are all forms of the suffixed definite article in Icelandic—the equivalent of the.

Icelandic usually attaches the to the end of the noun instead of using a separate word.

In this sentence:

• graskerin = grasker
  • definite ending = the pumpkins
• steinseljuna = steinselju-
  • definite ending = the parsley
• graslaukinn = graslauk-
  • definite ending = the chives / the chive plant

The exact form of the ending changes depending on:

• gender
• number
• case

Yes. While setja often literally means put or place, it is also very natural in practical contexts like gardening for putting/applying something somewhere.

So setjum áburð kringum ... means something like:

• we put fertilizer around ...
• we apply fertilizer around ...

In English, apply fertilizer may sound more natural, but Icelandic often uses a more literal verb like setja in this kind of sentence.

Yes. A perfectly normal version would be:

• Við setjum áburð kringum graskerin, steinseljuna og graslaukinn.

That simply means We put/apply fertilizer around the pumpkins, the parsley, and the chives.

Starting with Með garðáhöldunum adds emphasis to the means or method:

• With the garden tools, we apply fertilizer...

So the fronted phrase gives a slightly different focus, but the basic meaning stays the same.

A helpful way to map it is:

• Með garðáhöldunum = with the garden tools / using the garden tools
• setjum við = we put / we apply
• áburð = fertilizer
• kringum graskerin, steinseljuna og graslaukinn = around the pumpkins, the parsley, and the chives

So the sentence structure is roughly:

Using the garden tools, we apply fertilizer around the pumpkins, the parsley, and the chives.

That is a good example of several very common Icelandic features at once:

• a preposition taking case
• verb-second word order
• accusative direct object
• a preposition taking accusative
• suffixed definite articles on nouns