Пока брат копал землю у теплицы, я сажала клубнику возле старой яблони.

Here пока means while.

In this sentence, it connects two actions that were happening at the same time:

• Пока брат копал землю у теплицы...
• ...я сажала клубнику возле старой яблони.

So the idea is while my brother was digging, I was planting.

Russian пока can also mean until in other sentences, but here the context clearly shows simultaneous actions, so while is the right interpretation.

Both verbs are imperfective because the sentence describes two ongoing actions in progress at the same time.

• копал = was digging
• сажала = was planting

The focus is not on the result, but on the process.

If Russian used perfective verbs here, it would sound more like completed actions, which would change the meaning. For example:

• посадила would suggest planted completely / finished planting
• выкопал would suggest finished digging

So imperfective is the natural choice for background actions happening simultaneously.

Because Russian past tense agrees with gender.

For singular past tense verbs:

• masculine: сажал
• feminine: сажала
• neuter: сажало

So я сажала tells you the speaker is female.

If the speaker were male, it would be я сажал клубнику.

Клубнику is the accusative singular form of клубника.

It is accusative because сажать takes a direct object: you plant something.

• nominative: клубника
• accusative: клубнику

As for the singular: Russian often uses the singular when talking about a crop, a type of plant, or something understood as a category or mass.

So сажать клубнику very naturally means to plant strawberries / strawberry plants in a gardening sense.

English often prefers the plural here, but Russian singular is completely normal.

Землю is the accusative singular of земля.

It is used because копать also takes a direct object:

• копать что? → землю

Literally, this is to dig the earth/soil/ground.

In English, we often just say digging or digging the ground, but in Russian копать землю is a very common expression.

Because both are after prepositions that require the genitive case.

• у
  • genitive
• возле
  • genitive

So:

• теплица → у теплицы
• яблоня → возле яблони

The adjective also has to match the noun in case, gender, and number:

• старая яблоня
• возле старой яблони

So старой is genitive singular feminine, matching яблони.

Yes, both mean something like by / near / next to, but they are not always identical.

• у often gives the sense of right by, at, or beside
• возле means near or next to

In this sentence, both work well and the difference is small. The speaker may simply be using two different prepositions for natural style instead of repeating the same one twice.

So:

• у теплицы = by the greenhouse
• возле старой яблони = near the old apple tree

Yes, Russian word order is flexible.

This sentence starts with the пока clause because it sets the scene first:

• Пока брат копал землю у теплицы...

Then it gives the main clause:

• ...я сажала клубнику возле старой яблони.

You could rearrange it, for example:

• Я сажала клубнику возле старой яблони, пока брат копал землю у теплицы.

That would still be grammatical. The difference is mainly in emphasis and flow, not basic meaning.

Russian often leaves out possessive words like my, his, or her when the meaning is already obvious from context.

So брат can mean:

• my brother
• the brother
• sometimes just brother

depending on the situation.

Also, Russian has no articles, so there is no direct equivalent of a or the either.

That means context does a lot of work in Russian.

Sometimes yes, but the nuance changes.

• пока strongly suggests while, with overlap in time
• когда means when, and can be more neutral

So:

• Пока брат копал землю..., я сажала клубнику...
  = the two actions were going on at the same time

If you say:

• Когда брат копал землю..., я сажала клубнику...

it may still be understood, but пока is the more natural choice if you want to emphasize that both actions were happening simultaneously.

Because it must agree with яблони.

The base form is:

• старая яблоня = an old apple tree

After возле, the noun goes into the genitive:

• яблоня → яблони

The adjective has to change too:

• старая → старой

So:

• возле старой яблони

This is a standard adjective-noun agreement pattern in Russian.