Когда я смотрю на новый бутон, мне кажется, что орхидея скоро перестанет вянуть совсем.

Because смотреть usually takes the preposition на when it means to look at something.

• смотреть на что? = to look at something
• Я смотрю на бутон. = I’m looking at the bud.

Without на, смотреть usually means something more like to watch:

• смотреть фильм = to watch a film
• смотреть телевизор = to watch TV

So here смотрю на новый бутон is the normal way to say I look at the new bud.

In this sentence, бутон is the object of смотрю на, so it is indeed in the accusative:

• на что? → на новый бутон

But for masculine inanimate nouns, the accusative singular looks exactly like the nominative singular.

So:

• nominative: новый бутон
• accusative: новый бутон

That is why nothing changes in form. If it were an animate masculine noun, you would see a different ending pattern.

It can be understood as when in a general situation: when I look at the new bud.

Russian когда can work in both ways depending on context:

• a specific moment: When I arrived...
• a repeated/general situation: When I look at...

Here it sounds natural as a general observation, not necessarily one single event. The speaker is describing what happens in their mind whenever they look at the bud.

Because смотреть is imperfective, and that is what Russian normally uses for:

• ongoing actions
• repeated actions
• general present-time situations

So Когда я смотрю... means something like:

• When I look...
• When I am looking...

The perfective посмотреть does not normally have a true present tense. Its present-looking forms usually refer to the future:

• я посмотрю = I will have a look / I’ll look

That would not fit here.

Мне кажется means it seems to me. It expresses an impression, not a firm conclusion.

So there is a nuance:

• я думаю = I think
• мне кажется = it seems to me / I have the impression

In this sentence, the speaker is reacting to a sign—the new bud—and cautiously feels that the orchid may recover. So мне кажется is very natural.

It sounds a bit softer and less definite than я думаю.

Мне is dative case of я.

The structure is literally:

• мне кажется = to me, it seems

This is a very common Russian pattern:

• мне кажется = it seems to me
• ему кажется = it seems to him
• нам кажется = it seems to us

So Russian does not say I seem here. It uses an impersonal construction: it seems to me.

Because что introduces the content of what seems true.

• мне кажется, что... = it seems to me that...

So the sentence breaks down like this:

• Когда я смотрю на новый бутон = when I look at the new bud
• мне кажется = it seems to me
• что орхидея скоро перестанет вянуть совсем = that the orchid will soon stop wilting altogether

In everyday speech, Russians sometimes omit что, but in a full written sentence it is very normal to include it.

Перестать means to stop. It is followed by an infinitive:

• перестать + infinitive = to stop doing something

So:

• перестанет вянуть = will stop wilting

This is a very common construction:

• перестал работать = stopped working
• перестанет болеть = will stop hurting
• перестань говорить = stop talking

Here перестанет is future tense, because the speaker believes this change will happen soon.

Because after перестать, Russian normally uses an imperfective infinitive to describe the ongoing activity that stops.

• вянуть = to wilt, to be wilting
• перестать вянуть = to stop wilting

This focuses on the process.

A perfective verb like завянуть means something more like to wilt completely / to wither as a completed event. That would not fit well after перестать, because you are not stopping a completed event; you are stopping an ongoing process.

So перестанет вянуть is the natural choice.

Here совсем adds the idea of completely or altogether.

So:

• перестанет вянуть = will stop wilting
• перестанет вянуть совсем = will stop wilting altogether / completely stop wilting

It strengthens the statement.

Depending on context, совсем can mean different things, such as:

• completely
• entirely
• at all

In this sentence, altogether / completely is the best match.

Russian word order is flexible, and adverbs like совсем are often placed where they give the strongest emphasis.

Putting совсем at the end makes it sound emphatic:

• орхидея скоро перестанет вянуть совсем

It highlights the hopeful idea that the wilting may stop completely.

Other placements are possible in some contexts, but the final position here sounds natural and expressive.

Скоро means soon, and it modifies the future verb phrase:

• скоро перестанет вянуть = will soon stop wilting

So the idea is not just that the orchid will recover, but that the speaker thinks this may happen in the near future.

Because орхидея is the subject of the clause introduced by что:

• что орхидея скоро перестанет вянуть совсем

The orchid is the thing that will stop wilting, so it is the subject, and subjects are normally in the nominative case.

There are two commas for two different subordinate clauses.

1. Когда я смотрю на новый бутон, ...

   • The когда clause is subordinate, so it is separated by a comma.

2. мне кажется, что ...

   • The что clause is also subordinate, so it is separated by a comma.

So the punctuation reflects the structure:

• Когда... , мне кажется, что...

This is very standard Russian punctuation.

Yes, it is understandable and basically natural. It sounds like thoughtful, slightly careful speech.

A native speaker might also say something like:

• Когда я смотрю на новый бутон, мне кажется, что орхидея скоро совсем перестанет вянуть.
• Глядя на новый бутон, мне кажется, что орхидея скоро перестанет вянуть.

The original sentence is fine, though совсем before перестанет or before вянуть might sound a little more neutral to some speakers. At the end, it feels a bit more emphatic.