Вот бы этот бутон раскрылся к выходным.

Вот бы is a very common way to express a strong wish, often with an emotional tone.

In this sentence, it means something like:

• If only ...
• I wish ...
• Wouldn’t it be nice if ...

So Вот бы этот бутон раскрылся к выходным expresses hope or longing, not a plain statement of fact.

A rough feeling in English is:

• If only this bud opened by the weekend.
• I wish this bud would open by the weekend.

The word вот by itself often means here is / there is, but in вот бы it works as part of this wish-expression and should be understood as a set phrase.

This is one of the most important things to notice.

In Russian, after бы, a verb often appears in the past tense form, but the meaning is not necessarily past. It can express:

• a wish
• a hypothetical situation
• something unreal or desired

So раскрылся is formally the masculine singular past tense form, but with бы it means something like:

• would open
• opened in the sense of if only it opened

This is similar to English using past forms in unreal expressions:

• I wish it opened sooner
• If only it were true

So the form looks past, but the meaning is modal/hypothetical, not actually past time.

Because the speaker is not making a neutral prediction. They are expressing a wish.

Compare:

• Этот бутон раскроется к выходным.
  = This bud will open by the weekend.
  This is a statement/prediction.

• Вот бы этот бутон раскрылся к выходным.
  = If only this bud would open by the weekend.
  This is a wish.

So:

• раскроется = simple future
• раскрылся ... бы = wished-for / hypothetical result

In Russian, бы changes the whole mood of the sentence.

The verb раскрыться is perfective, and that makes sense because the speaker is talking about a completed result:

• not just the process of opening
• but the bud’s reaching the state of being open

With к выходным, the idea is by that time, I hope it will already have opened.

So perfective fits naturally because the speaker is focused on the endpoint.

Compare the aspectual idea:

• раскрываться = to be opening / to open repeatedly / process
• раскрыться = to open completely, to come open

Here the desired outcome is the completed event, so раскрылся is the right choice.

The -ся makes the verb reflexive/intransitive here.

Compare:

• раскрыть что-то = to open something
• раскрыться = to open up / to open on its own

A bud opens by itself, so Russian normally uses the reflexive form:

• бутон раскрылся = the bud opened

You would not usually say кто-то раскрыл бутон unless you mean someone physically opened it.

So -ся here helps show that the subject undergoes the action itself rather than acting on an object.

Because бутон is a masculine singular noun.

In the past tense, Russian verbs agree with the subject in:

• gender
• number

So:

• masculine singular: раскрылся
• feminine singular: раскрылась
• neuter singular: раскрылось
• plural: раскрылись

Since бутон is masculine, the verb must be раскрылся.

Because этот must agree with бутон in gender, number, and case.

Бутон is:

• masculine
• singular
• nominative here

So the demonstrative must also be masculine singular nominative:

• этот бутон = this bud

For comparison:

• эта роза = this rose
• это окно = this window
• эти цветы = these flowers

К выходным means by the weekend or toward the weekend.

In time expressions, к + dative often means:

• by a certain time
• for a certain point in time
• toward a certain time

So:

• к утру = by morning
• к вечеру = by evening
• к понедельнику = by Monday
• к выходным = by the weekend

In this sentence, the meaning is that the speaker hopes the bud will have opened by the time the weekend arrives.

Because the preposition к requires the dative case.

The basic dictionary form is:

• выходные = weekend / days off

When used after к, it becomes dative plural:

• к выходным

So the pattern is:

• nominative plural: выходные
• dative plural: выходным

Even though English says the weekend as if it were singular, Russian often uses the plural form выходные.

Because выходные literally means days off.

Russian conceptualizes the weekend as a pair/set of non-working days, so the plural is normal:

• на выходных = on the weekend
• к выходным = by the weekend
• после выходных = after the weekend

This is just one of those places where Russian and English package the idea differently.

The word order is natural, but it is not absolutely fixed.

Вот бы этот бутон раскрылся к выходным sounds smooth and neutral for expressing a wish about this bud specifically.

Russian word order can shift for emphasis. For example:

• Вот бы к выходным этот бутон раскрылся
  puts more focus on by the weekend
• Этот бутон вот бы раскрылся к выходным
  is possible, but less natural in ordinary speech

So the given order is a very normal way to present:

1. the wish marker
2. the subject
3. the desired event
4. the deadline/time expression

Not usually by itself, if you mean the same thing.

Если бы normally introduces a condition:

• Если бы этот бутон раскрылся к выходным, мы бы успели...
  = If this bud opened by the weekend, we would...

By contrast, Вот бы can stand alone as an emotional wish:

• Вот бы этот бутон раскрылся к выходным.

So if you want If only / I wish, then вот бы is the natural choice here.

It sounds natural and conversational, but not sloppy.

Вот бы is very common in everyday speech when expressing hopes or wishes. It is not especially formal, but it is perfectly standard Russian.

So this sentence would fit well in normal spoken language, for example when someone is looking at a plant and hoping it blooms in time.