La jardinera tiene sustrato para macetas.

It can mean either one, depending on context.

• jardinera = female gardener
• jardinera = planter / flower box / planting container

So this is one of those Spanish words that can be ambiguous by itself. The surrounding context usually makes it clear. Since the sentence also mentions sustrato para macetas, the intended meaning is very likely the gardening/container sense, not a person.

Because jardinera is feminine singular, so it takes the feminine singular article la.

Spanish articles must match the noun in gender and number:

• la jardinera = feminine singular
• las jardineras = feminine plural

If jardinera means planter, it is simply a feminine noun. If it means female gardener, it is feminine because it refers to a woman.

Tiene is the él/ella/usted form of tener, which means to have.

Since la jardinera is grammatically singular, Spanish uses the singular verb form:

• la jardinera tiene
• not la jardinera tienen

In this sentence, tiene can mean has in the sense of contains or has available.

Because sustrato is being treated as an uncountable material noun here, like soil, water, or sand in English.

So Spanish often says:

• tiene sustrato = it has potting medium / it has some substrate

rather than:

• tiene un sustrato

Using un sustrato would more often suggest a particular substrate or one type of substrate, not just some amount of the material.

In gardening, sustrato means the growing medium used for plants, especially in pots and containers. It is often more specific or technical than tierra.

So:

• tierra = soil, dirt, earth
• sustrato = substrate, growing medium, potting mix

In Latin American gardening vocabulary, sustrato is a very natural word, especially in stores, instructions, and plant care contexts. In casual speech, some people may also say tierra para macetas.

Because para expresses purpose or intended use.

• sustrato para macetas = substrate for pots
• de macetas would suggest something like from pots or of pots, which is not the intended idea here

So para is the normal choice when something is designed or used for a certain purpose, just like:

• agua para plantas
• abono para flores
• tierra para macetas

It is plural because the phrase is talking about pots in general, not one specific pot.

• para macetas = for pots / for flowerpots in general

Spanish often leaves out the article in this kind of general-purpose phrase, especially after para:

• ropa para niños
• vasos para agua
• comida para perros
• sustrato para macetas

If you said para las macetas, that would usually refer to specific pots already known in the conversation.

Yes, in many everyday situations it could.

For example:

• La jardinera tiene tierra para macetas.

That sounds more everyday and less technical. But sustrato is often a better word when talking about potting mix, planting medium, or a prepared material for container plants. So the choice depends on how precise the speaker wants to be.

This is the normal, neutral word order:

• La jardinera tiene sustrato para macetas.

That follows the common Spanish pattern:

subject + verb + object

You can change word order in Spanish, but doing so usually adds emphasis or sounds less neutral. For a basic statement, the original order is the most natural.