Learn Hardcore Polish: Na parapecie w kuchni stoi zielona roślina w czerwonej doniczce. - On the windowsill in the kitchen there is a green plant in a red flowerpot.

na + locative = location (where something is)
- na parapecie – on the windowsill (static location)
na + accusative = movement (where something goes)
- kładę roślinę na parapet – I put the plant onto the windowsill (movement onto)

In your sentence, the plant is simply standing there (no movement), so parapet goes into the locative case, which for this noun is parapecie.

Why do we say w kuchni instead of w kuchnia?

Again, this is the locative case after the preposition w with a static location.

Nominative (dictionary form): kuchnia
Locative (after w for “in” somewhere): w kuchni

Rules for a typical feminine noun ending in -a:

Nominative singular: -a → kuchnia
Locative singular: usually -y or -i → w kuchni

Because the plant is in the kitchen (static location, not movement into it), w kuchni is required.

Why is it zielona roślina but w czerwonej doniczce? Why do the adjectives have different endings?

They are in different cases.

zielona roślina
- This is the subject of the sentence.
- Case: nominative (who/what is standing?) → zielona roślina
- Noun: roślina – feminine singular
- Adjective in nominative feminine singular: zielona
w czerwonej doniczce
- This describes where the plant is (in what kind of pot).
- Preposition w for location demands the locative case.
- Noun: nominative doniczka → locative doniczce
- Adjective: nominative czerwona → locative feminine singular czerwonej

So:

Nominative feminine sg: zielona roślina, czerwona doniczka
Locative feminine sg: w czerwonej doniczce

What are the genders of parapet, kuchnia, roślina, and doniczka, and how can I tell?

parapet – masculine
- Ends in a consonant → usually masculine.
kuchnia – feminine
- Ends in -a → usually feminine.
roślina – feminine
- Also ends in -a.
doniczka – feminine
- Ends in -a and uses the typical feminine pattern (doniczka → doniczce in locative).

A quick rule of thumb:

Most nouns ending in a consonant = masculine
Most ending in -a = feminine
Most ending in -o, -e, -ę = neuter (with some exceptions)

Why do we use stoi instead of jest?

Polish often uses “posture verbs” for where objects are:

stoi – stands (vertical position, or objects that “stand”)
leży – lies (horizontal position)
wisi – hangs

Using stoi tells you:

The plant is upright, like an object that stands on a surface.
It sounds more natural and specific than jest in this context.

You could say W kuchni na parapecie jest zielona roślina, and it’s grammatically correct, but stoi sounds more visual and typical for items placed on surfaces.

Why is there no word for “a” or “the” before zielona roślina?

Polish has no articles (no equivalents of English “a/an” or “the”).

So zielona roślina can mean:

a green plant
the green plant

Which one is meant depends only on context, not on any extra word. The sentence structure itself doesn’t mark definiteness.

Can I change the word order, for example to Zielona roślina stoi na parapecie w kuchni? Does it change the meaning?

Yes, you can change the word order; Polish word order is relatively flexible.

Possible natural variants include:

Na parapecie w kuchni stoi zielona roślina w czerwonej doniczce. (original)
Zielona roślina w czerwonej doniczce stoi na parapecie w kuchni.
W kuchni na parapecie stoi zielona roślina w czerwonej doniczce.

The basic meaning stays the same. Differences:

Putting zielona roślina near the start slightly emphasizes what is there.
Starting with Na parapecie w kuchni emphasizes the location first.

All of these are natural and understandable.

What exactly is the grammatical structure of the sentence?

You can divide it like this:

Na parapecie w kuchni – a location phrase (two nested prepositional phrases)
- Na parapecie – on the windowsill
- w kuchni – in the kitchen (attached to parapecie: the windowsill in the kitchen)
stoi – verb, 3rd person singular, present, from stać (to stand)
zielona roślina w czerwonej doniczce – subject noun phrase
- zielona roślina – green plant (head noun + adjective)
- w czerwonej doniczce – prepositional phrase modifying roślina (plant in a red pot)

So structurally:

[Location] Na parapecie w kuchni + [Verb] stoi + [Subject] zielona roślina (w czerwonej doniczce)

Why do we have both na and w here? What’s the difference?

They express different spatial relations:

na = on (contact with a surface, usually from above)
- na parapecie – on the windowsill
w = in / inside
- w kuchni – in the kitchen
- w czerwonej doniczce – in the red pot

So the idea is:

The plant stands on the windowsill,
that windowsill is in the kitchen,
and the plant itself is in a red pot.

What’s the difference between na parapet and na parapecie, or do kuchni and w kuchni?

It’s about movement vs. location and case:

Static location (where something is)
- na + locative → na parapecie (on the windowsill)
- w + locative → w kuchni (in the kitchen)
Movement towards a place (where something goes)
- na + accusative → na parapet
  - Kładę roślinę na parapet. – I’m putting the plant onto the windowsill.
- do + genitive → do kuchni (to the kitchen)
  - Idę do kuchni. – I’m going to the kitchen.

So in your sentence we describe where the plant is (no movement), hence na parapecie, w kuchni, w czerwonej doniczce – all with static-location patterns.