Es probable que la semilla local germine.

Because es probable que expresses probability/uncertainty, and that normally triggers the subjunctive in Spanish.

• germina = indicative, used for facts or things presented as real
• germine = subjunctive, used here because the speaker is not stating a fact, only a possibility

So:

• La semilla local germina = The local seed germinates / is germinating / does germinate
• Es probable que la semilla local germine = It is likely that the local seed will germinate / may germinate

Germine is the present subjunctive form of germinar.

For -ar verbs, the present subjunctive endings are:

• yo: germine
• tú: germines
• él/ella/usted: germine
• nosotros: germinemos
• vosotros: germinéis
• ellos/ellas/ustedes: germinen

In your sentence, la semilla local is singular, so Spanish uses the él/ella/usted form: germine.

Normally, yes. Expressions like es probable que, es posible que, es dudoso que, and puede que usually take the subjunctive because they express doubt, possibility, or uncertainty.

Examples:

• Es posible que venga.
• Es probable que llueva.
• Es dudoso que lo sepan.

A useful rule of thumb is:

• certainty/fact → usually indicative
• doubt/possibility/judgment → often subjunctive

Because que introduces the subordinate clause: la semilla local germine.

In English, this is like that, although English often leaves that out:

• It is likely that the local seed will germinate.

In Spanish, you normally need que here:

• Es probable que la semilla local germine.

Without que, the sentence would be ungrammatical.

Yes. Semilla is a feminine noun, so it takes:

• the article la
• any agreeing adjectives in their feminine form, if they have separate masculine/feminine forms

So:

• la semilla
• una semilla

Here, local does not visibly change for gender, but it still agrees grammatically with semilla.

Because many Spanish adjectives do not have separate masculine and feminine singular forms.

Local is one of those adjectives:

• el producto local
• la semilla local

The adjective stays local in both masculine and feminine singular.

It only changes in the plural:

• los productos locales
• las semillas locales

In this sentence, it most naturally refers to the future from the speaker’s point of view.

So although the form is present subjunctive, the meaning is basically:

• It is likely that the local seed will germinate

This is very common in Spanish. The present subjunctive is often used after expressions like es probable que to talk about something that has not happened yet.

Yes, you could, and it is natural. But the structure is slightly different.

• Es probable que la semilla local germine = It is likely that the local seed will germinate
• Probablemente la semilla local germinará = The local seed will probably germinate

Both are correct, but:

• es probable que + subjunctive sounds a bit more like a formal statement of probability
• probablemente + future/indicative is often more direct

You may also hear:

• Probablemente la semilla local germine

After probablemente, both indicative and subjunctive can appear, depending on how much uncertainty the speaker wants to express.

Because ser is used for general assessments, descriptions, and statements like it is probable, it is important, it is necessary, etc.

So Spanish says:

• Es probable
• Es posible
• Es importante
• Es necesario

Using estar here would sound wrong.

A helpful way to think of it is that es probable gives a general judgment about the situation, not a temporary physical state.

Yes, but the original order is the most neutral and standard:

• Es probable que la semilla local germine.

You could also hear:

• Es probable que germine la semilla local.

That version is grammatically correct, but it shifts the rhythm and focus slightly. The original sentence is usually the safest choice for learners.

Here local means from the local area or native to that place/context.

So la semilla local could mean:

• a seed from the local region
• a locally sourced seed
• a native/local variety, depending on context

In other words, local is describing the seed as belonging to or coming from the area being discussed.

Yes, it is completely natural in Spanish from Spain.

It sounds neutral and correct, especially in contexts like:

• agriculture
• gardening
• ecology
• botany
• seed varieties or crop studies

In everyday conversation, a Spaniard might also say something slightly simpler depending on context, but this sentence itself is perfectly normal.