Кактус почти не вянет даже тогда, когда почва сухая уже два дня.

In Russian, почти не + verb is the normal way to say almost doesn’t... or hardly...

So:

• почти не вянет = almost does not wilt / hardly wilts

If you said не почти вянет, it would sound wrong in normal Russian.

This is a very common pattern:

• я почти не ем сахар = I hardly eat sugar
• он почти не спит = He hardly sleeps

So it is best to learn почти не as a unit.

Russian often uses the present tense to describe a general fact or regular behavior.

Here, Кактус почти не вянет... means something like:

• a cactus almost never wilts in that situation
• a cactus does not wilt much under those conditions

It is not about one single moment only. It is a general statement.

Also, вянет is imperfective, which fits well because the sentence describes an ongoing process or tendency, not a single completed result.

Because the sentence talks about a process/state, not a completed event.

• вянуть = to wilt, to be wilting
• perfective forms would usually focus on reaching the result, like to wilt completely

Here the idea is:

• the cactus does not really go into that wilting process much

So imperfective is the natural choice for a general truth or repeated situation.

It means even when.

Literally, it is built as:

• даже = even
• тогда = then
• когда = when

So word-for-word it is something like even then, when...

In natural English, you usually just say even when.

Both are possible.

• даже когда почва сухая уже два дня = even when the soil has been dry for two days
• даже тогда, когда почва сухая уже два дня = even when the soil has been dry for two days

The version with тогда, когда is a correlative structure. It sounds a bit more explicit and sometimes a bit more formal or emphatic.

So:

• даже когда = shorter, simpler
• даже тогда, когда = slightly more structured/emphatic

Both are correct.

In Russian, the verb to be is normally omitted in the present tense.

So:

• почва сухая literally looks like soil dry
• but it means the soil is dry

This is completely normal in Russian.

Compare:

• он дома = he is at home
• вода холодная = the water is cold
• почва сухая = the soil is dry

If you were talking about the past or future, Russian would use forms of быть:

• почва была сухая = the soil was dry
• почва будет сухая = the soil will be dry

Because сухая agrees with почва.

• почва is feminine singular
• so the adjective must also be feminine singular: сухая

Also, here сухая is a predicate adjective after an omitted is, so it stays in the nominative:

• почва сухая = the soil is dry

Forms like сухой or сухую would be used in other grammatical roles:

• с сухой почвой = with dry soil
• сухую почву = dry soil (object)

Here it means for two days already or has been ... for two days.

So:

• почва сухая уже два дня = the soil has been dry for two days already

Russian often expresses duration with just a time expression, without a preposition like for.

Examples:

• я жду тебя два часа = I’ve been waiting for you for two hours
• он живёт здесь три года = he has lived here for three years

The word уже adds the idea of already.

After the numerals 2, 3, 4, Russian usually uses the noun in the genitive singular.

So:

• два дня = two days
• три часа = three hours
• четыре года = four years

That is why it is два дня, not два дней.

The form дней is genitive plural and would be used in other situations, for example:

• пять дней = five days
• много дней = many days

Почва is in the nominative case.

That is because it is the subject of the sentence:

• Кактус = subject of the main clause
• почва = subject of the subordinate clause

In the subordinate clause:

• почва сухая уже два дня = the soil has been dry for two days

So почва is the thing being described as dry, which makes nominative the correct case.

Russian has no articles.

So кактус can mean:

• a cactus
• the cactus
• cactus, as a general kind

And почва can mean:

• soil
• the soil
• the ground

English has to choose an article, but Russian usually leaves that to context.

In this sentence, English might naturally say either:

• A cactus hardly wilts...
• The cactus hardly wilts...
• Cactus hardly wilts... (less natural in English, but possible in a general statement)

The Russian sentence itself does not mark that distinction.

It can be understood generically: Russian often uses the singular to talk about a whole class of things.

So Кактус почти не вянет... can mean something like:

• a cactus does not wilt much...
• cacti do not wilt much...

The exact English translation depends on context. Russian singular is often used for general truths like this.

Yes. Russian word order is flexible, although each version may sound slightly different in emphasis.

For example, this would also be understandable:

• Кактус почти не вянет, даже когда почва уже два дня сухая.

This version may sound a little more natural to some speakers because уже два дня is placed closer to сухая.

The original sentence is still correct. Russian often moves words around for rhythm, focus, or style more freely than English.