Flores collecti in aqua ponuntur.

Collecti agrees with flores.

• flores = flowers
• It is nominative plural masculine
• So the participle describing it must also be nominative plural masculine

That is why we get collecti, not collectus or collectae.

Latin adjectives and participles have to match the noun they describe in gender, number, and case.

Collecti is a perfect passive participle of colligo (to gather, collect).

It literally means something like:

• having been gathered
• gathered
• collected

So flores collecti means gathered flowers or more literally flowers having been gathered.

In this sentence, the participle works almost like an adjective describing the flowers.

Because ponuntur is a present passive verb.

It comes from pono, ponere = to place, put.

The ending -untur tells you it is:

• 3rd person plural
• present tense
• passive voice

So ponuntur means:

• they are placed
• they are put

Since flores is plural, the verb is plural too.

Because in Latin, the verb ending already includes that idea.

In English, we say the flowers are placed with two words. In Latin, ponuntur by itself already means they are placed.

You can break it down roughly like this:

• pon- = place / put
• -untur = they are being done passively

So Latin often packs more information into one word than English does.

Because it follows in meaning in in the sense of location.

With in, Latin uses:

• ablative for location: in the water
• accusative for motion into: into the water

Here the flowers are being placed in water, so Latin uses in aqua.

So:

• in aqua = in water
• in aquam would mean into the water

It can mean either, depending on context.

Latin has no word for the or a/an, so aqua can be understood as:

• water
• the water
• some water

The exact English wording depends on the situation and the translation style.

Latin word order is more flexible than English word order because the endings show how the words function.

This sentence is arranged quite naturally:

• Flores collecti = the subject with its description
• in aqua = where the action happens
• ponuntur = the verb at the end

Putting the verb at the end is very common in Latin, though not required.

So the order is natural Latin, even though English would usually say: The collected flowers are placed in water.

Yes.

Depending on how literal or smooth you want the English to be, flores collecti could be:

• collected flowers
• gathered flowers
• flowers that have been gathered
• flowers having been gathered (more literal)

In normal English, gathered flowers or the flowers, once gathered may sound more natural than a very literal participle translation.

It is passive overall.

The key sign is ponuntur = are placed.

That means the subject, flores collecti, is not doing the action. Instead, the flowers are receiving the action.

So:

• active would be something like someone places the flowers in water
• passive is the flowers are placed in water

Yes, either is possible.

Because ponuntur is present tense, it can mean:

• are placed right now
• are usually placed
• get placed

So the sentence might describe:

• an action happening at the moment
• a regular practice
• a general instruction or procedure

You decide from context.