Sans bon terreau, les tomates du potager grandissent moins vite.

After sans, French very often leaves out the article when speaking in a general way.

So sans bon terreau means something like without good soil / without any good growing medium in a broad sense.

Compare:

• sans bon terreau = without good soil in general
• sans un bon terreau = without a specific good soil
• sans du bon terreau = much less natural here

This article drop is very common after sans:

• sans eau
• sans argent
• sans aide

So sans bon terreau is the natural general phrasing.

Because terreau is a masculine noun.

In French, adjectives must agree with the noun they describe:

• masculine singular: bon terreau
• feminine singular: bonne terre
• masculine plural: bons terreaux
• feminine plural: bonnes terres

Since terreau is masculine singular, the adjective is bon.

Terreau is not just ordinary earth or soil in the broadest sense. It usually refers to a rich growing medium, compost-like soil, or potting soil used for plants.

That is why bon terreau suggests soil that is suitable for helping plants grow well.

A learner might compare:

• terre = earth, ground, soil
• sol = soil, ground, surface
• terreau = rich planting soil, compost-rich growing medium, potting soil

So terreau is a more gardening-specific word.

French often uses the definite article to talk about things in a general sense.

So les tomates can mean tomatoes as a class, or the tomatoes in a context where the group is already identified.

In English, we often drop the article in general statements:

• Tomatoes grow quickly
• Cats like milk

But French usually keeps it:

• Les tomates...
• Les chats...

Here, les tomates du potager refers to the tomatoes from that vegetable garden, so the definite article is completely natural.

Du here is the contraction of de + le.

• le potager = the vegetable garden
• de le potager becomes du potager

So les tomates du potager means the tomatoes of/from the vegetable garden.

This du is not the partitive article here. It is simply the contraction of de + le showing possession or origin.

Compare:

• le livre du professeur = the teacher’s book
• les tomates du potager = the tomatoes from the vegetable garden

Because the full noun is le potager. In this sentence, potager is being used as a noun meaning vegetable garden.

French gender is something you usually have to learn with each noun:

• le potager = masculine
• la tomate = feminine
• le terreau = masculine

That is why we get du potager and not de la potager.

Because the subject is les tomates, which is third person plural.

The verb is grandir in the present tense:

• je grandis
• tu grandis
• il/elle grandit
• nous grandissons
• vous grandissez
• ils/elles grandissent

Since les tomates = they, the correct form is grandissent.

The present tense in French is often used for general truths, habits, and regular facts.

So this sentence is not necessarily describing what is happening at this exact second. It can express a general rule:

Without good soil, the tomatoes in the vegetable garden grow less quickly.

This is very normal in both French and English:

• Les plantes ont besoin d’eau.
• Les tomates grandissent moins vite sans bon terreau.

It states a general fact about how tomatoes grow.

French often puts a condition or context at the beginning of the sentence for emphasis or clarity.

So Sans bon terreau sets the scene first: Without good soil, ...

Then the main clause follows: les tomates du potager grandissent moins vite

This is similar to English:

• Without enough water, plants suffer.
• In winter, the days are shorter.

The comma helps separate the introductory phrase from the main statement.

Both are possible, but moins vite is very common and natural in everyday French.

• moins vite = less quickly / not as fast
• plus lentement = more slowly

They are close in meaning, but moins vite often sounds simpler and more conversational.

So:

• Les tomates grandissent moins vite = very natural
• Les tomates grandissent plus lentement = also correct, slightly more formal or stylistically heavier

French often prefers vite in ordinary speech.

Yes, depending on the nuance.

• grandir focuses on becoming bigger, growing in size
• pousser often focuses on growing as a plant, sprouting, developing

So:

• Les tomates grandissent moins vite = the tomatoes grow bigger more slowly
• Les tomates poussent moins vite = the tomatoes grow more slowly as plants

Both can work, but grandissent emphasizes size increase a bit more.