Marie prend soin de la plante.

Because the subject is Marie, which is third-person singular (she).

The verb prendre in the present tense goes like this:

• je prends = I take
• tu prends = you take
• il/elle/on prend = he/she/one takes

So with Marie, you use elle forms, which gives Marie prend.

Prendre soin de is a fixed expression meaning to take care of.

Even though prendre by itself usually means to take, you should learn prendre soin de as one unit:

• prendre soin de quelqu’un = to take care of someone
• prendre soin de quelque chose = to take care of something

So in this sentence, don’t translate word by word too literally. The whole phrase is what matters.

Because the expression is prendre soin de. The de is required by the phrase.

So you say:

• Marie prend soin de la plante.
• Il prend soin de son chien.
• Nous prenons soin des enfants.

You cannot just remove the de. It is part of the structure.

Because after prendre soin de, French requires de before the noun.

Since plante is feminine singular, the normal article is la. After the required de, you get:

• de + la plante = de la plante

Compare:

• le livre → du livre
• la plante → de la plante
• les plantes → des plantes

So de la plante is just de + la plante.

Because in French, every noun has a grammatical gender. Plante is a feminine noun, so it uses feminine articles and adjectives.

That is why you say:

• la plante = the plant

If you referred to it with a pronoun, you would use elle in French grammar, even though in English we usually say it for objects.

Yes, it is natural and correct.

Another common way is with s’occuper de:

• Marie s’occupe de la plante.

Both can mean Marie takes care of the plant, but prendre soin de can sometimes sound a bit more attentive or caring, as if Marie is carefully looking after it.

Yes. It works for both.

Examples:

• Elle prend soin de sa grand-mère. = She takes care of her grandmother.
• Il prend soin de sa voiture. = He takes care of his car.
• Nous prenons soin des plantes. = We take care of the plants.

So it is a very useful expression for both people and objects.

A simple approximation is:

ma-REE prahn swan duh la plant

A few pronunciation notes:

• Marie sounds like ma-REE
• prend has a nasal vowel; the d is usually not strongly pronounced
• soin also has a nasal sound, roughly like swan but more nasal
• de is often a light duh
• plante sounds close to plant, but with the French vowel quality

Depending on speed and accent, de may sound very light in natural speech.

It is the present tense: Marie prend soin de la plante.

In English, this can often translate as either:

• Marie takes care of the plant
• Marie is taking care of the plant

French present tense often covers both a general present and an ongoing present, depending on context.

Yes, depending on the noun that follows.

Because the expression requires de, it combines with the article:

• de + le = du
• de + la = de la
• de + les = des

Examples:

• Marie prend soin du jardin. = Marie takes care of the garden.
• Marie prend soin de la plante. = Marie takes care of the plant.
• Marie prend soin des plantes. = Marie takes care of the plants.

So the form changes according to the gender and number of the noun.

Usually la plante means the plant in the sense of a living plant.

However, in some contexts, plante can have other meanings, and in informal language it can even be slang in certain expressions. But in a basic sentence like Marie prend soin de la plante, the natural meaning is definitely a houseplant or another living plant.

No, the word order is quite standard:

Subject + verb + expression + noun

• Marie = subject
• prend = verb
• soin de la plante = what she is taking care of

So the sentence structure is very normal for French. The main thing to learn is that soin and de belong together in the expression prendre soin de.