Αποκλείεται να σαπίσουν οι ρίζες.

Here Αποκλείεται means It’s impossible, There’s no way, or Out of the question.

In everyday Greek, it is very often used as an impersonal expression:

• Αποκλείεται. = No way. / Impossible.
• Αποκλείεται να... = It’s impossible that... / There’s no way ...

So in Αποκλείεται να σαπίσουν οι ρίζες, the speaker is saying that the roots rotting is considered impossible.

Yes, formally it is a middle/passive form of the verb αποκλείω.

• αποκλείω = exclude, rule out
• αποκλείεται literally has the sense of is ruled out

That is why the whole expression works like:

• Αποκλείεται να σαπίσουν οι ρίζες.
• Literally: It is ruled out that the roots rot
• Natural English: It’s impossible for the roots to rot

So even though it looks like a passive verb form, in this sentence it functions as a very common fixed impersonal expression.

Because Greek normally uses να to introduce a subordinate clause after expressions of possibility, impossibility, desire, fear, necessity, and so on.

So:

• Αποκλείεται να σαπίσουν... = It’s impossible that they rot / for them to rot

You cannot normally leave να out here in standard Greek.

Compare:

• Θέλω να φύγω = I want to leave
• Μπορεί να βρέξει = It may rain
• Αποκλείεται να σαπίσουν οι ρίζες = It’s impossible for the roots to rot

So να is the normal linker before the verb in this kind of clause.

Σαπίσουν is the 3rd person plural aorist subjunctive form of σαπίζω.

Here is the breakdown:

• σαπίζω = I rot / I make rot
• σαπίσουν = they rot in a να-clause, viewed as a single whole event

Why 3rd person plural?

Because the subject is οι ρίζες = the roots, which is plural.

So:

• οι ρίζες σαπίσουν would correspond to the roots rot
• but after να, Greek uses the subjunctive structure: να σαπίσουν

Not exactly. It is not a future tense form by itself.

It is a subjunctive form, used here after να.

English often translates it with a future idea because the sentence is about whether something may happen later, but grammatically Greek is doing something different.

Compare:

• Θα σαπίσουν οι ρίζες. = The roots will rot.
  This is future.

• Αποκλείεται να σαπίσουν οι ρίζες. = It’s impossible for the roots to rot.
  This is not future tense; it is a να + subjunctive clause.

So a learner should not think of σαπίσουν itself as meaning will rot. The idea of possibility/impossibility comes from Αποκλείεται, not from the verb form alone.

This is a question of aspect, which is very important in Greek.

• να σαπίσουν = aorist subjunctive
  This presents the rotting as a whole event: to rot, to end up rotting

• να σαπίζουν = present/imperfective subjunctive
  This would suggest an ongoing or repeated process: to be rotting, to rot repeatedly

In this sentence, Greek chooses σαπίσουν because the speaker is talking about the event as a whole: whether the roots will rot or not.

So:

• Αποκλείεται να σαπίσουν οι ρίζες. = There’s no way the roots will rot
• Αποκλείεται να σαπίζουν οι ρίζες. would sound more like There’s no way the roots are rotting / would be rotting, which is a different nuance.

Yes, Greek word order is more flexible than English.

In this sentence, οι ρίζες comes after σαπίσουν, which is perfectly natural:

• Αποκλείεται να σαπίσουν οι ρίζες.

This word order is common, especially after an impersonal expression like Αποκλείεται.

You can also move the subject for emphasis:

• Οι ρίζες αποκλείεται να σαπίσουν.
  This puts more emphasis on the roots.

So the original order is natural, but not the only possible one.

Greek uses the definite article much more often than English.

• οι ρίζες = the roots

In context, this usually means specific roots already understood from the situation, such as the roots of a plant being discussed.

Without the article, ρίζες would sound more indefinite or less anchored in context. Greek often prefers the article when talking about known or identifiable things.

So even if English might sometimes say just roots, Greek often naturally says οι ρίζες.

Οι ρίζες is nominative feminine plural.

• singular: η ρίζα = the root
• plural: οι ρίζες = the roots

It is nominative because it is the subject of σαπίσουν.

So in this sentence:

• σαπίσουν = rot
• οι ρίζες = the roots
• together: the roots rot

Because Αποκλείεται is being used impersonally.

The plural subject οι ρίζες belongs to the verb σαπίσουν, not to Αποκλείεται.

So the structure is really:

• Αποκλείεται = It is impossible
• να σαπίσουν οι ρίζες = for the roots to rot

The main verb stays in 3rd person singular because it works like English it is impossible, where it is also impersonal.

Yes, very often.

Greek speakers commonly say just:

• Αποκλείεται!

This means:

• No way!
• Impossible!
• Absolutely not!

Then, if they want, they can add a να clause to say what is impossible:

• Αποκλείεται να σαπίσουν οι ρίζες.

So the sentence you have is built from a very common everyday expression.