Semeei salsa no canteiro.

Semeei is the 1st person singular form of semear in the pretérito perfeito simples — the tense usually used for a completed action in the past.

So it means I sowed / I planted (specifically by sowing seeds).

• eu semeei = I sowed
• The action is presented as finished.

Portuguese often leaves out the subject pronoun when the verb ending already makes the subject clear.

Here, semeei already tells you the subject is eu because the ending -ei marks I in this tense.

So both of these are possible:

• Semeei salsa no canteiro.
• Eu semeei salsa no canteiro.

The version without eu is very natural and common.

Because the verb is semear, and when it is conjugated in this form, the stem and the ending come together as -eei.

• infinitive: semear
• past, eu form: semeei

So the spelling is regular, not a typo.

This also happens with some other verbs ending in -ear, for example:

• passear → passeei
• nomear → nomeei

This is a very useful distinction.

• semear = to sow seeds
• plantar = to plant, often more generally, or to put a plant/seedling into the ground

So Semeei salsa suggests that the speaker sowed parsley seeds.

If you were putting a young plant into the soil, plantei salsa could be more appropriate.

In everyday speech, though, people may sometimes use plantar more loosely.

Yes. In Portuguese, salsa means parsley.

This can surprise English speakers because salsa in English usually makes people think of the sauce or the dance. But in Portuguese, salsa is the herb.

A helpful related word:

• coentros = coriander / cilantro

Because Portuguese often uses a bare noun in this kind of context, especially when talking about what someone sowed, planted, bought, grew, etc.

So Semeei salsa sounds natural and means something like:

• I sowed parsley
• I sowed some parsley

Using a salsa is possible in some contexts, but it would usually sound more specific or definite, as if you were talking about a particular parsley plant, batch, or known parsley.

No is a contraction of:

• em = in / on / at
• o = the

So:

• em + o = no

That means no canteiro = in the garden bed / in the flower bed

This happens very often in Portuguese:

• na = em + a
• nos = em + os
• nas = em + as

Because in Portuguese, em + article normally contracts.

So em o canteiro is not the normal form. The correct form is:

• no canteiro

This kind of contraction is standard and expected, not optional in normal usage.

A canteiro is a prepared strip or patch of soil for growing plants. Depending on context, it can be:

• a flower bed
• a garden bed
• a vegetable bed

In this sentence, it most likely means a part of the garden or vegetable patch where herbs are grown.

So no canteiro gives the idea of sowing the parsley in the bed of soil, not just somewhere generally in the garden.

Yes, it is very natural.

The order is:

• verb: Semeei
• direct object: salsa
• place: no canteiro

That is a very common and neutral structure in Portuguese.

You could change the order for emphasis, but Semeei salsa no canteiro is the straightforward, standard way to say it.