На поляне трава была мокрой, и под берёзой стояла скамейка.

Because на is followed by the prepositional case when it means in/on/at a location.

• поляна = meadow, clearing
• на поляне = in the clearing / on the meadow

Here the sentence is talking about where the grass was, not motion toward the clearing, so Russian uses the prepositional.

Compare:

• на поляне = in the clearing
• на поляну = onto the clearing / to the clearing

Because под takes the instrumental case when it means under/beneath in a static location.

• берёза = birch tree
• под берёзой = under the birch tree

This is a very common pattern:

• под столом = under the table
• под окном = under the window
• под берёзой = under the birch tree

If there were motion to a position under something, Russian could use a different case:

• поставить под берёзу = to place something under the birch tree

But here the bench is already there, so instrumental is used.

Because after была (“was”), Russian often uses the adjective in the instrumental case.

• трава была мокрой = the grass was wet

This is a very common pattern with быть in the past or future:

• Он был усталым = He was tired
• Она была счастливой = She was happy
• Трава была мокрой = The grass was wet

You may also hear трава была мокрая. That is possible too, but мокрой is very standard and natural here.

So the short answer is:

• мокрой is instrumental feminine singular
• it is used because it is the predicate adjective after была

Because the subject is трава, which is feminine singular.

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

• он был = he was
• она была = she was
• оно было = it was
• они были = they were

Since трава is feminine, the verb must be была.

Because скамейка is also feminine singular, and past-tense verbs agree with their subject.

• скамейка = bench
• стояла = stood / was standing

So:

• под берёзой стояла скамейка = under the birch tree there was a bench / a bench stood under the birch tree

Just like with была, the ending -а shows feminine singular past tense.

Russian often uses verbs like стоять (“to stand”), лежать (“to lie”), and висеть (“to hang”) where English might simply say there is/was.

So скамейка стояла literally means the bench stood, but in natural English it often means:

• there was a bench
• a bench stood there
• a bench was standing there

Russian likes to describe the physical position of objects more explicitly than English does.

Russian word order is flexible, and it often changes the focus or scene-setting rather than the basic meaning.

Starting with На поляне puts the location first:

• На поляне трава была мокрой = In the clearing, the grass was wet

This feels natural if the speaker is first describing the setting.

If you said:

• Трава на поляне была мокрой

that would also be correct, but the emphasis would be a little different. It sounds more like the grass in the clearing was wet, perhaps in contrast with grass somewhere else.

So the original order is very normal for descriptive narration.

Again, this is about information structure.

• под берёзой стояла скамейка

This order first gives the location (under the birch tree) and then introduces what was there (a bench). That is very natural in Russian when presenting a scene.

It is a bit like English:

• Under the birch tree stood a bench.

Russian often places the newly introduced thing later in the clause.

Russian has no articles like a/an/the.

So:

• трава can mean grass or the grass
• скамейка can mean a bench or the bench

You understand it from context.

In this sentence, English would usually say:

• the grass was wet
• a bench stood under the birch tree

Why? Because grass is often understood as general/background material, while bench is being introduced as something newly noticed in the scene.

But Russian itself does not mark that with articles.

Трава is in the nominative case, because it is the subject of the clause.

• трава была мокрой = the grass was wet

The subject of a sentence is usually nominative in Russian.

So in the first clause:

• трава = nominative
• была = past tense verb agreeing with трава
• мокрой = instrumental predicate adjective

Скамейка is also in the nominative case, because it is the subject of the second clause.

• под берёзой стояла скамейка

Even though it comes at the end, it is still the thing doing the “standing,” so it is the subject and stays nominative.

This is important: in Russian, the subject does not have to come first.

И means and. It joins two clauses:

1. На поляне трава была мокрой
2. под берёзой стояла скамейка

So the sentence is simply describing two things in the same scene:

• the grass was wet
• there was a bench under the birch tree

Yes. ё is always pronounced yo and is normally stressed.

So:

• берёза sounds roughly like bih-RYO-zuh
• берёзой sounds roughly like bih-RYO-zoy

In many Russian texts, ё is often written as е, but the correct pronunciation is still ё if the word is берёза.

So even if you saw под березой in a text, you would still pronounce it берёзой.

Yes, that is one helpful way to think about it.

With быть, the instrumental often presents a quality as a state or condition of the subject:

• трава была мокрой = the grass was in a wet state

That is why it sounds very natural in a descriptive sentence like this.

However, do not treat this as a strict “temporary vs permanent” rule in every case. Russian is more flexible than that. The safest learner rule is:

• after был / была / было / были, predicate nouns and many predicate adjectives are often in the instrumental

That rule will help you understand sentences like this one correctly.

You can do a rough literal breakdown, but natural English will usually sound different.

Word by word:

• На поляне = in the clearing
• трава = grass
• была = was
• мокрой = wet
• и = and
• под берёзой = under the birch tree
• стояла = stood
• скамейка = bench

A very literal translation would be:

• In the clearing the grass was wet, and under the birch tree stood a bench.

That is understandable English, but a more natural English version might be:

• The grass in the clearing was wet, and there was a bench under the birch tree.

So yes, you can break it down literally for study, but good English may rearrange things.