Learn Hardcore Greek: Δίπλα στην πηγή υπάρχουν φυτά που είναι πάντα πράσινα και όμορφα. - Next to the spring there are plants that are always green and beautiful.

Πηγή is feminine, so it takes the feminine article την in the accusative after σε. In speech you will almost never hear σε την πηγή; it’s always contracted to στην πηγή.

Why is πηγή in the accusative case after σε instead of some other case?

In Modern Greek, the preposition σε (in, at, to) is followed by the accusative case.

η πηγή (nominative – subject form)
την πηγή (accusative – after σε)

So:

η πηγή είναι εκεί = the spring is there
πάω στην πηγή = I go to the spring
δίπλα στην πηγή = next to the spring

The choice of accusative is simply a fixed rule of the language: σε + accusative, never nominative or genitive.

Why does the sentence start with Δίπλα στην πηγή instead of starting with Υπάρχουν φυτά?

Greek word order is fairly flexible. Starting with Δίπλα στην πηγή puts emphasis on the place first:

Δίπλα στην πηγή υπάρχουν φυτά…
→ At / Next to the spring, there are plants…

You could also say:

Υπάρχουν φυτά δίπλα στην πηγή που είναι πάντα πράσινα και όμορφα.

Both are grammatically correct. The original order just foregrounds the location, which is very natural in Greek narrative or descriptive sentences.

What is the difference between υπάρχουν and είναι here? Could I say Στην πηγή είναι φυτά?

Υπάρχουν comes from υπάρχω (to exist). In this kind of sentence, υπάρχουν corresponds to English there are:

Υπάρχουν φυτά… = There are plants…

You can say:

Δίπλα στην πηγή είναι φυτά…

but it sounds less natural and a bit odd in standard modern Greek; είναι is more like are in the sense of are located / are these things, not the neutral existential there are. When you introduce the existence of something in a place, υπάρχουν is the default:

Στο δωμάτιο υπάρχουν τρία παράθυρα. = There are three windows in the room.

So in your sentence, υπάρχουν is the best, most idiomatic choice.

Why is there no article before φυτά? Why not υπάρχουν τα φυτά?

Φυτά here is an indefinite plural: plants in general, not specific plants already known.

In Greek, when you talk about some / any / unspecified plural things in an existential sentence, you usually omit the article:

Υπάρχουν φυτά… = There are (some) plants…
Υπάρχουν σπίτια εκεί. = There are houses there.

If you said:

Υπάρχουν τα φυτά…

it would sound like you are talking about particular, known plants (for example, plants that were mentioned just before), and even then it’s a bit unnatural; you would normally just say:

Τα φυτά δίπλα στην πηγή είναι πάντα πράσινα και όμορφα.
= The plants next to the spring are always green and beautiful.

So: no article → general, indefinite; article → specific, known.

What exactly is που doing in φυτά που είναι πάντα πράσινα και όμορφα?

Here που is a relative pronoun, similar to that / which in English:

φυτά που είναι πάντα πράσινα και όμορφα
= plants that are always green and beautiful

Key points:

που is invariable (it doesn’t change form for gender, number, or case).
It is used all the time in everyday Greek for who / that / which in relative clauses.
Don’t confuse it with πού (with an accent), which is the question word where?

More formal Greek can also use ο οποίος / η οποία / το οποίο, but που is by far the most common choice in speech.

Why are the adjectives πράσινα and όμορφα in the neuter plural form?

They agree with φυτά, which is neuter plural:

το φυτό → τα φυτά (neuter plural)
so adjectives must also be neuter plural nominative:
- πράσινο → πράσινα (neuter plural)
- όμορφο → όμορφα (neuter plural)

Agreement rules:

Gender: neuter
Number: plural
Case: nominative (because φυτά is the subject of είναι)

So you get:
φυτά (neuter plural) → πράσινα και όμορφα (neuter plural)

What is the role of πάντα, and where can it go in the sentence?

Πάντα means always and here it modifies the adjectives πράσινα και όμορφα:

είναι πάντα πράσινα και όμορφα
= they are always green and beautiful

Typical positions for πάντα:

Before the adjective phrase: είναι πάντα πράσινα
Before the verb (more emphatic, often spoken): πάντα είναι πράσινα (sounds a bit heavier, more contrastive)

In this sentence, είναι πάντα πράσινα και όμορφα is the most neutral and natural word order.

Is there a difference between δίπλα σε and κοντά σε? Could I say Κοντά στην πηγή υπάρχουν φυτά…?

Yes, you can say:

Κοντά στην πηγή υπάρχουν φυτά που είναι πάντα πράσινα και όμορφα.

The difference:

δίπλα σε = right next to / immediately beside
κοντά σε = near / close to, but not necessarily touching or immediately adjacent

So δίπλα στην πηγή is a bit more precise: the plants are basically beside the spring, not just somewhere nearby.

Why is it στην πηγή and not στη πηγή? What is the rule with that final -ν?

The full form is στην = σε + την.

In Modern Greek, the final -ν of την / στην is:

kept before vowels and certain consonants like π, τ, κ, ξ, ψ, μπ, ντ, γκ, τσ, τζ
often dropped in other cases (τη γυναίκα, στη θάλασσα)

Because πηγή starts with π, you keep the -ν:

στην πηγή (standard spelling)
Not στη πηγή in careful writing.

So the sentence uses the standard orthographic rule.

Could I move things around and say Υπάρχουν πάντα πράσινα και όμορφα φυτά δίπλα στην πηγή? Does it change the meaning?

Yes, you can say:

Υπάρχουν πάντα πράσινα και όμορφα φυτά δίπλα στην πηγή.

That means roughly the same thing: There are always green and beautiful plants next to the spring.

Differences:

Original: φυτά που είναι πάντα πράσινα και όμορφα
→ focuses on a description of those plants.
Alternative: πάντα πράσινα και όμορφα φυτά
→ treats always green and beautiful as a fixed quality of those plants, more compactly.

Both are correct and natural. The relative clause version (που είναι…) is slightly more explanatory or descriptive in style.