Las flores pueden florecer en primavera con tal de que las reguemos cada mañana.

In Spanish, general nouns often use the definite article where English does not.

So las flores can mean either:

• the flowers (specific flowers), or
• flowers in a general sense, depending on context.

Here, because the sentence later says las reguemos (that we water them), it sounds like we are probably talking about a particular set of flowers, not flowers in general.

Pueden florecer means can bloom or are able to bloom. It expresses possibility or ability.

• Las flores florecen en primavera = Flowers bloom in spring / The flowers bloom in spring
• Las flores pueden florecer en primavera = The flowers can bloom in spring

With pueden, the sentence suggests that blooming depends on a condition, which is then given in the second half: con tal de que las reguemos cada mañana.

That is because they are related words:

• flor = flower
• flores = flowers
• florecer = to bloom / to flower

So the sentence uses two related words:

• las flores = the flowers
• florecer = to bloom

This kind of repetition is completely normal in Spanish.

After en, Spanish often uses the season without the article:

• en primavera = in spring
• en verano = in summer
• en otoño = in autumn
• en invierno = in winter

You may sometimes hear en la primavera, but en primavera is very common and natural.

Con tal de que means provided that, as long as, or on condition that.

It introduces a condition that must be met.

So:

• Las flores pueden florecer en primavera con tal de que las reguemos cada mañana.
• The flowers can bloom in spring provided that we water them every morning.

It is a fixed expression, so it is best learned as a whole chunk: con tal de que.

Because con tal de que is one of the expressions that normally trigger the subjunctive in Spanish.

It introduces a condition that is not simply being stated as a fact, but as something required or dependent on something else.

That is why you get:

• con tal de que las reguemos

and not:

• con tal de que las regamos

The subjunctive here signals uncertainty, condition, or non-factuality.

Reguemos is the present subjunctive, nosotros form, of regar (to water).

The verb forms are:

• yo riegue
• tú riegues
• él/ella riegue
• nosotros/nosotras reguemos
• vosotros/vosotras reguéis
• ellos/ellas rieguen

Here, reguemos means we water in a subjunctive context:

• provided that we water them

This is a spelling change to preserve pronunciation.

The verb is regar. In forms where the ending begins with e, Spanish adds u so that the g keeps its hard sound.

Compare:

• regar → regamos
• regar → reguemos

Without the u, regemos would sound wrong, because ge in Spanish is pronounced like a strong h-sound. The u keeps the sound like g in go.

So:

• regar = reh-GAR
• reguemos = reh-GEH-mos, with the normal hard g

Las is the direct object pronoun meaning them, referring back to las flores.

So:

• regar las flores = to water the flowers
• regarlas = to water them
• que las reguemos = that we water them

Spanish often replaces a repeated noun with an object pronoun, just as English does.

Because reguemos is a conjugated verb, and object pronouns normally go before conjugated verbs.

So:

• que las reguemos = correct

You do not say:

• que reguemoslas = incorrect

Pronouns can go after the verb with:

• infinitives: regarlas
• gerunds: regándolas
• affirmative commands: regadlas / riégalas

But with a normal conjugated form like reguemos, the pronoun goes before it.

By itself, reguemos can sometimes look like a let’s... form, because the nosotros subjunctive is also used for first-person plural commands.

For example:

• Reguemos las flores. = Let’s water the flowers.

But in this sentence, it is clearly not a command because it comes after con tal de que, which requires the subjunctive:

• con tal de que las reguemos = provided that we water them

So here it is not let’s water them; it is a subjunctive clause.

Both are possible, but they are slightly different in feel.

• cada mañana = every morning
• todas las mañanas = every morning / all mornings

In many contexts they are almost interchangeable. Cada mañana often sounds a little more like a regular repeated routine.

So:

• las reguemos cada mañana = we water them every morning

is very natural.

Yes, depending on context, poder can express:

• ability: can
• possibility: may / might
• permission: can / may

In this sentence, pueden florecer is mainly about possibility or ability:

• The flowers can bloom in spring
• The flowers may bloom in spring

In natural English, can bloom is probably the best match here.

A rough pronunciation would be:

las FLO-res PWE-den flo-re-THER en pri-ma-BE-ra kon tal de ke las re-GHE-mos KA-da ma-NYA-na

A few key Spain-Spanish points:

• z in florecer is pronounced like th in thin
• c before e/i is also pronounced like th in most of Spain
• ll and y are usually pronounced similarly
• ñ in mañana sounds like ny in canyon

So florecer in Spain is approximately flo-re-THER, while in much of Latin America it would sound more like flo-re-SER.

Yes, it is grammatical and natural. It has a slightly careful, textbook-style structure because of con tal de que, but it is perfectly good Spanish.

A native speaker might also say things like:

• Las flores pueden florecer en primavera si las regamos cada mañana.
• Las flores florecerán en primavera si las regamos cada mañana.

But the original sentence is absolutely correct and useful, especially for learning how conditional expressions trigger the subjunctive.