A erva daninha não murchou sequer.

Because erva daninha is a specific noun phrase, and Portuguese often uses the definite article where English might not.

• a = the
• erva daninha = weed / literally harmful plant

So A erva daninha means The weed.

In Portuguese, using the article is very natural here. Leaving it out would usually sound less complete unless you were speaking very generally or using the phrase in a special context.

Erva daninha is the usual expression for weed.

Literally:

• erva = herb / grass / plant
• daninha = harmful, damaging, noxious

So the literal sense is something like harmful plant, but in normal English the best translation is simply weed.

Because it agrees with erva, which is a feminine noun.

• erva is feminine
• adjectives normally agree in gender and number with the noun

So:

• erva daninha = feminine singular
• ervas daninhas = feminine plural

If the noun were masculine, the adjective would usually change too:

• animal daninho = harmful animal

Murchou is the pretérito perfeito simples in Portuguese, which usually corresponds to the simple past in English.

It comes from the verb murchar = to wilt, to wither, sometimes to droop.

Conjugation:

• eu murchei
• tu murchaste
• ele/ela/você murchou
• nós murchámos
• vós murchastes
• eles/elas/vocês murcharam

So não murchou means did not wilt / hasn’t wilted, depending on context in English.

Because Portuguese does not need an extra auxiliary like English did to form the negative in the past.

English:

• The weed did not wilt

Portuguese:

• A erva daninha não murchou

The tense is already shown by the form murchou, so Portuguese just adds não before the verb.

Here sequer means even, especially in a negative context.

So:

• não murchou sequer = didn’t even wilt

It adds emphasis: not only did the weed survive, it did not even show the smallest sign of wilting.

In many contexts, sequer appears with a negative idea:

• não respondeu sequer = he didn’t even reply
• nem sequer tentou = he didn’t even try

In Portuguese, sequer can come after the verb phrase for emphasis, and that sounds natural here.

So:

• A erva daninha não murchou sequer.

This structure highlights the complete lack of wilting.

You may also see:

• A erva daninha nem sequer murchou.

That version is also very common and perhaps even more immediately recognisable to learners because nem sequer often clearly means not even.

Both are natural, but the sentence with final sequer has a slightly compact, emphatic feel.

Both can express not even, but nem sequer is often more explicit.

• não murchou sequer
• nem sequer murchou

Both mean roughly the same thing here.

Very roughly:

• sequer alone can sound a bit more compact or stylistically neat
• nem sequer is very common and very clear in everyday use

In negative sentences, learners will often meet nem sequer first.

No, that word order is not natural.

The normal options are:

• A erva daninha não murchou sequer.
• A erva daninha nem sequer murchou.

Portuguese has fairly natural patterns for negative emphasis, and sequer usually does not go before não like that.

Yes, murchar is a very natural verb for plants and flowers.

It means:

• to wilt
• to wither
• to droop

It describes losing freshness, firmness, or moisture.

Examples:

• As flores murcharam. = The flowers wilted.
• A planta está a murchar. = The plant is wilting.

So in your sentence, the idea is that the weed stayed so strong that it didn’t even wilt.

It is singular because it refers to one weed:

• A erva daninha não murchou sequer.

If you wanted the plural:

• As ervas daninhas não murcharam sequer.

Changes:

• a → as
• erva → ervas
• daninha → daninhas
• murchou → murcharam

It works in both, but the style may feel slightly more formal or literary depending on context.

In European Portuguese, it sounds perfectly natural.

In Brazilian Portuguese, people would also understand it, though in everyday speech many speakers might prefer:

• A erva daninha nem murchou.
• A erva daninha nem sequer murchou.

So the sentence is valid in both varieties, but the frequency and feel of sequer may vary a bit.

The sentence is strongly emphatic.

It does not just say the weed survived. It says the weed was so unaffected that it didn’t even wilt.

That makes it useful in contexts such as:

• describing resilience
• expressing surprise
• contrasting with other plants that suffered

So the emotional tone is something like:

• Even after everything, the weed showed no sign of weakness at all.