Βάλε κομπόστ και λίπασμα στο υπόστρωμα του φυτού εσωτερικού χώρου.

Βάλε is the singular imperative of βάζω (to put / to place / to add).

So it is used when speaking to one person:

• Βάλε = put / add
• Βάλτε = put / add when speaking to more than one person or in a polite/formal way

It is specifically the aorist imperative, which usually gives the sense of one complete action: add it / put it in.

στο is the normal contraction of σε + το.

• σε = in / into / to / on depending on context
• το = the for a neuter singular noun

So:

• σε το υπόστρωμα becomes στο υπόστρωμα

This is completely standard Greek.

Here υπόστρωμα means the growing medium or potting substrate of the plant — basically the material the plant is growing in.

Depending on context, it can be translated as:

• substrate
• potting mix
• growing medium
• sometimes loosely soil

In gardening language, υπόστρωμα is often a bit more technical than just ordinary soil.

Because they are being used in a general, indefinite sense:

• κομπόστ = compost
• λίπασμα = fertilizer

Greek often leaves out the article with substances or materials when you mean them generally, just like English often does.

So this means:

• add compost and fertilizer not
• add the compost and the fertilizer

If you meant specific known compost and fertilizer, Greek could use articles:

• το κομπόστ και το λίπασμα

του φυτού is in the genitive singular.

• το φυτό = the plant (nominative/accusative)
• του φυτού = of the plant

The genitive is used here to show a relationship like of:

• το υπόστρωμα του φυτού = the plant’s substrate / the substrate of the plant

So the phrase tells you whose substrate we are talking about.

This is a very common Greek way to say indoor plant.

Literally:

• φυτό = plant
• εσωτερικού χώρου = of interior space / indoor

So:

• φυτό εσωτερικού χώρου = indoor plant

In your sentence, this appears inside the genitive phrase:

• του φυτού εσωτερικού χώρου = of the indoor plant

The part εσωτερικού χώρου describes the kind of plant:

• not an outdoor plant
• but an indoor plant

Because it is a fixed descriptive structure built around χώρος (space), which appears in the genitive:

• εσωτερικού = interior / indoor in genitive form
• χώρου = space in genitive singular

Together:

• εσωτερικού χώρου = of indoor space / indoor

Greek often uses this type of noun phrase where English would prefer an adjective:

• φυτό εσωτερικού χώρου = indoor plant
• literally, plant of indoor space

So the genitive here is part of the expression itself.

Because του introduces the whole noun phrase.

Greek does not need another article before εσωτερικού χώρου here. That part is attached to φυτού and helps define what kind of plant it is.

So the structure is:

• του φυτού = of the plant
• εσωτερικού χώρου = modifying plant, meaning indoor

Together:

• του φυτού εσωτερικού χώρου = of the indoor plant

No, Greek word order is fairly flexible.

The given sentence:

• Βάλε κομπόστ και λίπασμα στο υπόστρωμα του φυτού εσωτερικού χώρου.

is perfectly natural.

But Greek could also rearrange parts for emphasis, for example:

• Βάλε στο υπόστρωμα του φυτού εσωτερικού χώρου κομπόστ και λίπασμα.

Both mean essentially the same thing. The difference is mainly about focus and style, not basic meaning.

They are related, but not the same:

• κομπόστ = compost, organic decomposed material added to improve the growing medium
• λίπασμα = fertilizer, a substance added mainly to provide nutrients

So κομπόστ improves the structure and organic content of the substrate, while λίπασμα is more specifically about feeding the plant.

That is why the sentence mentions both: they are not exact synonyms.

You would change Βάλε to Βάλτε:

• Βάλτε κομπόστ και λίπασμα στο υπόστρωμα του φυτού εσωτερικού χώρου.

Everything else stays the same.

So:

• Βάλε = singular informal
• Βάλτε = plural or polite singular