Fræin spíra ekki þegar moldin er of köld.

In Icelandic, the is usually attached to the noun as a suffix rather than written as a separate word.

• fræin = fræ
  • definite ending = the seeds
• moldin = mold
  • definite ending = the soil

So instead of a separate article like English the, Icelandic often builds definiteness into the noun itself.

Because Icelandic definite endings depend on gender, number, and case, and sometimes different forms happen to look the same.

Here:

• fræin = definite plural of a neuter noun
• moldin = definite singular of a feminine noun

So the endings look alike, but they are not the same grammatical form.

A useful comparison:

• fræið = the seed
• fræin = the seeds

Because the subject is fræin (the seeds), which is plural.

The verb að spíra conjugates like this in the present tense:

• ég spíra
• þú spírar
• hann/hún/það spírar
• við spírum
• þið spírið
• þeir/þær/þau spíra

So with a 3rd person plural subject like fræin, the correct form is spíra.

Compare:

• Fræið spírar. = The seed sprouts.
• Fræin spíra. = The seeds sprout.

In a normal Icelandic main clause, ekki usually comes after the finite verb.

So:

• Fræin spíra ekki.

This is different from English, where we often use do not.

English:

• The seeds do not sprout

Icelandic:

• literally more like The seeds sprout not

That word order is completely normal in Icelandic.

Because the subject of that clause is moldin, which is singular.

So the verb að vera (to be) must also be singular:

• moldin er = the soil is

If the subject were plural, you would use eru instead.

This is a good reminder that each clause has its own subject and verb:

• main clause: Fræin spíra ekki
• subordinate clause: þegar moldin er of köld

Because Icelandic adjectives must agree with the noun they describe in gender, number, and case.

The noun moldin is:

• feminine
• singular
• nominative

So the adjective kaldur (cold) changes to the feminine singular nominative form:

• kaldur = masculine
• köld = feminine
• kalt = neuter

That is why the sentence has:

• moldin er of köld

No. of means too, not very.

So:

• of köld = too cold
• mjög köld = very cold

That distinction matters:

• very cold just describes the temperature
• too cold means cold enough to cause a problem

In this sentence, of shows that the coldness prevents the seeds from sprouting.

Here þegar means when.

It introduces a subordinate clause:

• þegar moldin er of köld = when the soil is too cold

Inside that clause, Icelandic usually has normal subject + verb order:

• moldin er
• not er moldin

So þegar is acting as a conjunction that connects the two parts of the sentence.

Yes. You can say:

• Þegar moldin er of köld, spíra fræin ekki.

That is also correct.

But notice what happens in the main clause: Icelandic is a V2 language in main clauses, so when the sentence starts with the subordinate clause, the finite verb comes before the subject in the main clause:

• Þegar moldin er of köld, spíra fræin ekki.

Not:

• Þegar moldin er of köld, fræin spíra ekki.

So fronting the when-clause changes the word order in the main clause.

In this sentence:

• fræin is nominative plural because it is the subject of spíra
• moldin is nominative singular because it is the subject of er
• köld is also nominative, because it is a predicate adjective after vera (to be) and agrees with moldin

So even though Icelandic has a rich case system, this sentence stays fairly simple: the main noun forms here are nominative.