Potteplanten trenger plantelyset, ikke minst fordi vinteren er mørk.

Because potteplanten is the definite singular form of potteplante (potted plant / houseplant).

• en potteplante = a potted plant
• potteplanten = the potted plant

In Norwegian, definiteness is often added as a suffix to the noun instead of using a separate word like the.

It is a compound noun, which is very common in Norwegian.

It is made from:

• potte = pot
• plante = plant

So potteplante literally means pot-plant, i.e. potted plant / houseplant.

Then the definite ending -n / -en is added:

• potteplante = potted plant
• potteplanten = the potted plant

Trenger is the present tense of å trenge, which means to need.

So:

• Potteplanten trenger plantelyset = The potted plant needs the grow light

A learner may notice that Norwegian does not use do-support like English does. You simply say:

• Planten trenger lys = The plant needs light
• Trenger planten lys? = Does the plant need light?

Because Norwegian usually writes compound nouns as one word.

Here:

• plante = plant
• lys = light

Together:

• plantelys = plant light / grow light

And the sentence uses the definite singular form:

• et plantelys = a grow light
• plantelyset = the grow light

The ending is -et because lys is a neuter noun:

• et lys
• lyset

Since plantelys is built on lys, it keeps that neuter pattern.

Ikke minst is an expression meaning something like:

• especially
• not least
• particularly

In this sentence, it emphasizes the reason that follows:

• Potteplanten trenger plantelyset, ikke minst fordi vinteren er mørk.
• The potted plant needs the grow light, especially because winter is dark.

So the speaker may have several reasons in mind, and this is an important one.

Because fordi means because and introduces a subordinate clause.

In Norwegian subordinate clauses, the word order is normally:

subject + verb

So:

• fordi vinteren er mørk = because the winter is dark / because winter is dark

Compare:

• Main clause: Vinteren er mørk.
• Subordinate clause: fordi vinteren er mørk

This is normal Norwegian clause structure.

Vinteren is the definite singular form of vinter:

• en vinter = a winter
• vinteren = the winter

In Norwegian, the definite form is often used for something general, familiar, or understood from context. Here vinteren can refer to the winter season in general, especially the winter in the place being talked about.

So even though English often says winter with no article, Norwegian may naturally say vinteren.

Because mørk is a predicate adjective after er.

In Norwegian, when an adjective comes after a verb like være (to be), it usually agrees like this:

• singular common gender: mørk
• singular neuter: mørkt
• plural / definite attributive contexts: often mørke

Here the subject is vinteren, which is singular and common gender, so:

• vinteren er mørk = correct

Compare:

• en mørk vinter = a dark winter
• vinteren er mørk = the winter is dark
• et mørkt rom = a dark room
• rommet er mørkt = the room is dark

In ordinary Norwegian punctuation, a comma before a subordinate clause like one introduced by fordi is often used, especially in clear written style.

Here the comma helps separate:

• the main statement: Potteplanten trenger plantelyset
• the added explanation: ikke minst fordi vinteren er mørk

So the comma is natural and helpful. You should expect to see this kind of punctuation in written Norwegian.

Yes, if the context makes it clear which plant you mean.

• Planten = the plant
• Potteplanten = the potted plant / houseplant

Using potteplanten is more specific. It tells us this is a plant growing in a pot, not just any plant.

So both are possible, but they are not equally specific.

The dictionary forms are:

• potteplante = potted plant / houseplant
• å trenge = to need
• plantelys = grow light / plant light
• ikke minst = especially / not least
• fordi = because
• vinter = winter
• mørk = dark

The sentence itself uses inflected forms:

• potteplanten = definite singular
• trenger = present tense
• plantelyset = definite singular
• vinteren = definite singular
• mørk = singular predicate adjective