In hortō rosae et lilia flōrent, et avia dīcit hortum hodiē pulchriōrem esse quam herī.

Because in hortō means in the garden, and after in with the meaning of location, Latin normally uses the ablative.

• hortus = garden as the dictionary form, nominative singular
• hortō = ablative singular
• in hortō = in the garden

If in meant movement into the garden, Latin would usually use the accusative instead: in hortum.

They are the things doing the action of flōrent (bloom), so they are in the nominative case, which is the normal case for subjects.

• rosae = roses (nominative plural)
• lilia = lilies (nominative plural)

So the sentence begins with:

• In hortō rosae et lilia flōrent = In the garden, roses and lilies are blooming

Because they belong to different declensions and have different plural endings.

• rosa, rosae is a first-declension noun
  
  • nominative plural: rosae
• lilium, liliī is a second-declension neuter noun
  
  • nominative plural: lilia

A very important pattern is that neuter plural nominative often ends in -a.

So:

• rosae = roses
• lilia = lilies

Even though lilia ends in -a, it is plural, not singular.

Because its subject is plural: rosae et lilia = roses and lilies.

• flōret = blooms / is blooming for one thing
• flōrent = bloom / are blooming for more than one thing

Since there are two subjects joined by et (and), Latin uses the plural verb.

Avia is the subject of dīcit.

• avia = grandmother
• dīcit = says

So:

• avia dīcit = grandmother says

Then what follows is what grandmother says.

Because Latin often uses indirect statement after verbs of saying, thinking, knowing, hearing, and so on. In this construction, the subject of the reported statement goes into the accusative, and the verb goes into the infinitive.

So instead of saying something like:

• the garden is more beautiful

Latin says, after dīcit:

• hortum ... esse = literally the garden to be ...

That is why:

• hortus would be nominative
• hortum is accusative, because it is the subject of the infinitive esse inside indirect statement

For the same reason: this is the standard Latin accusative-and-infinitive construction for indirect statement.

After dīcit, Latin does not usually say:

• avia dīcit hortus est...

Instead it says:

• avia dīcit hortum ... esse...

So:

• est = is
• esse = to be

But in this construction, esse is best understood not as a simple English to be, but as part of a reported statement:

• avia dīcit hortum hodiē pulchriōrem esse quam herī
• grandmother says that the garden is more beautiful today than yesterday

Because it is a comparative adjective agreeing with hortum.

The base adjective is:

• pulcher = beautiful

Its comparative is:

• pulchrior = more beautiful

In the sentence, it must match hortum, which is:

• masculine
• singular
• accusative

So the form becomes:

• pulchriōrem = masculine/feminine accusative singular of the comparative

In other words:

• hortum pulchriōrem = the garden more beautiful

More naturally in English: the garden to be more beautiful

Because comparative adjectives in Latin are declined like third-declension adjectives, not like ordinary -us, -a, -um adjectives.

For example:

• positive: pulcher, pulchra, pulchrum = beautiful
• comparative: pulchrior (masc./fem.), pulchrius (neut.) = more beautiful

So forms like pulchriōrem may look unfamiliar at first, but they are normal for comparatives.

Herī is an adverb, meaning yesterday. It does not change case because adverbs do not decline like nouns.

Here quam introduces the comparison:

• hodiē pulchriōrem ... quam herī = more beautiful today than yesterday

In full logic, the comparison really means something like:

• more beautiful today than it was yesterday

Latin often leaves out words that are easily understood. So quam herī is a compact way of saying than yesterday.

Yes, you can think of it that way. Latin often omits repeated or obvious words.

The fuller idea is:

• hortum hodiē pulchriōrem esse quam herī erat
• the garden to be more beautiful today than it was yesterday

But Latin does not need to repeat all that. Once the meaning is clear, quam herī is enough.

This kind of ellipsis is very common.

Latin word order is more flexible than English word order. Hodiē is an adverb meaning today, and it modifies the statement about the garden being more beautiful.

So:

• hortum hodiē pulchriōrem esse
• literally, the garden today to be more beautiful

In smoother English:

• that the garden is more beautiful today

Latin often places adverbs near the word or idea they emphasize, but the sentence would still be understandable if the order changed.

Because the sentence has two separate places where and is needed.

First:

• rosae et lilia = roses and lilies

Second:

• ... flōrent, et avia dīcit ... = ... are blooming, and grandmother says ...

So the first et joins two nouns, and the second et joins two larger parts of the sentence.

To an English speaker, it may feel a little flexible, but it is perfectly normal Latin.

Latin often puts a prepositional phrase like in hortō near the beginning to set the scene:

• In hortō = In the garden

Then it gives the subject:

• rosae et lilia

Then the verb:

• flōrent

English could also do something similar:

• In the garden, roses and lilies are blooming.

So the order is natural and clear in Latin.

Yes. Latin present tense can often be translated in more than one way depending on context.

• dīcit can mean says
• or is saying

Likewise:

• flōrent can mean bloom
• or are blooming

In a simple sentence like this, English usually prefers:

• In the garden roses and lilies are blooming, and grandmother says that the garden is more beautiful today than yesterday.

But the exact English tense choice depends on style.