En el rellano hay una planta pequeña.

In Spain, rellano usually means a landing: the flat space at the top, bottom, or between flights of stairs.

So En el rellano means on the landing or in the hallway landing area, depending on the building.

In some contexts, especially in apartment buildings in Spain, rellano can also refer to the shared space just outside the front doors of the flats on a floor.

Hay means there is / there are and is used to say that something exists somewhere.

So:

• En el rellano hay una planta pequeña. = There is a small plant on the landing.

You use está when you are talking about the location of something specific or already known:

• La planta está en el rellano. = The plant is on the landing.

A useful contrast:

• Hay una planta... → introduces the plant
• La planta está... → talks about where the plant is

Because planta is a feminine noun in Spanish.

So both the article and the adjective have to agree with it:

• una planta
• planta pequeña

Agreement is very important in Spanish:

• masculine singular: un libro pequeño
• feminine singular: una planta pequeña

Even though some nouns ending in -a can occasionally be masculine, planta is a regular feminine noun.

In Spanish, adjectives often come after the noun, especially when they describe a basic, literal quality.

So:

• una planta pequeña = a small plant

That is the most neutral, standard order.

You can also say:

• una pequeña planta

But that can sound a bit more literary, expressive, or subjective depending on context. In many beginner situations, the safest pattern is:

• noun + adjective
• planta pequeña, casa grande, libro interesante

Yes, you can.

Both are grammatical, but they are not always felt in exactly the same way:

• una planta pequeña → a plant that is small, straightforward description
• una pequeña planta → often slightly more descriptive, expressive, or stylistic

In everyday speech, una planta pequeña is very natural.

Because in Spanish, only two common contractions happen with el:

• a + el = al
• de + el = del

But:

• en + el = en el
  not a contraction

So En el rellano is correct.

No. Hay is the same for both singular and plural.

So you say:

• Hay una planta pequeña. = There is a small plant.
• Hay dos plantas pequeñas. = There are two small plants.

This is different from English, where there is and there are change.

Because estar does not normally work like English there is.

Spanish usually uses:

• hay + noun to say something exists
• estar to locate something specific

So these are correct:

• En el rellano hay una planta pequeña.
• La planta pequeña está en el rellano.

But está una planta pequeña is not the normal way to express there is a small plant.

Yes, somewhat.

En el rellano hay una planta pequeña is very natural because it starts with the place and then says what is there.

You could also say:

• Hay una planta pequeña en el rellano.

That means the same thing.

Both are correct. The version with En el rellano first gives a bit more focus to the location.

In most of Spain, rellano is pronounced approximately like:

• reh-YA-no

The ll is usually pronounced like y in modern Spanish.

So:

• re-ll-a-no → reh-YA-no

Depending on the region, the exact sound may vary slightly, but for most learners, using a y sound is perfectly fine.

Because una planta introduces the plant as something not previously identified.

• una planta = a plant
• la planta = the plant

If the listener does not already know which plant you mean, una is the normal choice.

Compare:

• En el rellano hay una planta pequeña. = There is a small plant on the landing.
• La planta pequeña está en el rellano. = The small plant is on the landing.

The second version sounds like both people already know which plant is being talked about.