Wenn wir das Beet im Mai düngen, blühen die Rosen oft bis in den Herbst.

Because wenn introduces a subordinate clause. In German, the conjugated verb in a subordinate clause normally goes to the end.

• Wenn wir das Beet im Mai düngen
• literally: If/when we the flowerbed in May fertilize

That is standard German word order after conjunctions like wenn, weil, dass, and obwohl.

German main clauses follow the V2 rule: the finite verb must be in the second position.

Here, the entire wenn-clause comes first, and it counts as position 1:

1. Wenn wir das Beet im Mai düngen
2. blühen
3. die Rosen oft bis in den Herbst

So the verb blühen has to come immediately after the opening clause.

Here wenn expresses a general condition, so it can feel like if, when, or even whenever, depending on context.

In this sentence, the idea is something like:

• If we fertilize the flowerbed in May, the roses often bloom into autumn
• or When we fertilize the flowerbed in May, the roses often bloom into autumn

It is not talking about one specific past event. It is more of a general pattern.

Because Beet is a neuter noun: das Beet.

Also, in this sentence it is the direct object of düngen, so it is in the accusative case. For neuter nouns, the article das stays the same in nominative and accusative:

• nominative: das Beet
• accusative: das Beet

So das Beet is correct.

Beet usually means a flowerbed, garden bed, or planted bed in a garden.

So das Beet düngen means to fertilize the flowerbed/garden bed.

It does not mean a whole garden; it refers to a specific planted area.

im is a contraction of in dem.

• in dem Mai would be wrong here
• im Mai is the standard form

German often uses in + dative with months:

• im Mai = in May
• im Sommer = in summer

So this is just the normal way to say in May.

German often uses the present tense to talk about the future, especially when the time is already clear from context.

Here, im Mai and the overall meaning make the future/general sense obvious:

• Wenn wir ... düngen, blühen ...
• literally present tense, but naturally understood as a future or general result

English does something similar in sentences like If we fertilize them in May, they bloom longer.

Because die Rosen is plural, so the verb must also be plural.

• singular: die Rose blüht
• plural: die Rosen blühen

That is why the sentence uses blühen.

oft means often. It tells you that this result happens frequently, not always.

It is placed in the main clause after the subject:

• blühen die Rosen oft bis in den Herbst

This is a very natural position for an adverb like oft. It comes after the verb and subject here, before the final time expression.

bis in den Herbst means into the autumn/fall, emphasizing that the blooming continues and reaches into that season.

It suggests extension well into autumn, not just up to its beginning.

• bis in den Herbst = into autumn
• bis zum Herbst = until autumn / up to autumn

So bis in den Herbst gives a stronger sense of continuation.

Because in can take either the dative or the accusative.

Here it is part of the expression bis in den Herbst, which has a sense of movement or extension into a period of time, so German uses the accusative:

• in den Herbst

This is similar to spatial expressions where in + accusative means movement into something.

Yes. In German, a subordinate clause introduced by wenn must be separated from the main clause by a comma.

So this is required:

• Wenn wir das Beet im Mai düngen, blühen die Rosen oft bis in den Herbst.

The comma is not optional.

Yes, but the meaning changes slightly.

• wenn is neutral and common for general conditions
• falls means in case or if it happens that, and can sound a bit more tentative

In this sentence, wenn is the most natural choice because it describes a regular gardening cause-and-effect relationship.

Yes: German often places time expressions before the verb at the end of a subordinate clause.

So this order is very natural:

• wir das Beet im Mai düngen

You could also hear different word orders in other contexts, but this one sounds smooth and standard:

• subject: wir
• object: das Beet
• time: im Mai
• verb: düngen

Yes. That is also correct German:

• Die Rosen blühen oft bis in den Herbst, wenn wir das Beet im Mai düngen.

The meaning stays basically the same. The main difference is emphasis:

• starting with Wenn ... emphasizes the condition
• starting with Die Rosen ... emphasizes the result