Learn Hardcore Indonesian: Besok saya menanam tomat lagi, karena tanaman itu tumbuh cepat di cuaca cerah. - Tomorrow I will plant tomatoes again, because that plant grows fast in clear weather.

Indonesian verbs don’t change for tense. Time words do the work. Besok (tomorrow) already sets it in the future. You can add akan for intention or a slightly more formal tone: both Besok saya menanam tomat lagi and Besok saya akan menanam tomat lagi are correct.

Where should I put lagi, and can it also mean “currently”?

Here lagi means “again,” and the natural placement is after the verb phrase: menanam tomat lagi. If you say lagi menanam tomat, in everyday Indonesian that usually means “is currently planting tomatoes” (progressive). To avoid ambiguity when you mean “again,” keep lagi after the object: Saya menanam tomat lagi. Synonyms: kembali (more formal), lagi-lagi (repeatedly, often with a slightly negative tone).

Is tomat singular or plural here? How do I say “tomatoes”?

Indonesian nouns don’t inflect for number, so tomat can mean “tomato” or “tomatoes.” Make it explicit if needed:

some tomatoes: beberapa tomat
many tomatoes: banyak tomat
two tomatoes (the fruits): dua buah tomat
two tomato plants: dua tanaman tomat Reduplication (tomat-tomat) marks plural in formal writing but is rarely needed in speech.

What exactly does tanaman itu refer to? Is it the tomatoes?

tanaman itu means “that plant”/“the plant,” pointing to something specific already known. If you mean tomato plant(s), say it explicitly:

karena tanaman tomat itu tumbuh cepat …
or more generally: karena tanaman tomat tumbuh cepat … In casual talk you might hear tomat cepat tumbuh, but tanaman tomat is clearer.

Is di cuaca cerah idiomatic? What are more natural options?

It’s understandable, but Indonesians more often frame weather as a time/condition:

saat cuaca cerah / ketika cuaca cerah = when the weather is sunny
kalau cuacanya cerah = if/when it’s sunny (informal)
pada saat cuaca cerah = formal So a very natural version is: …, karena tanaman itu tumbuh cepat saat cuaca cerah.

Do I need the comma before karena?

When the main clause comes first, a comma before karena … is optional and often omitted. If the karena-clause comes first, you should use a comma: Karena …, besok saya …. Keeping the comma for readability is fine either way.

Difference between karena and sebab? And what about soalnya, jadi, makanya?

karena and sebab both mean “because.” karena is the default; sebab is a bit more formal/written.
soalnya is colloquial “because”: …, soalnya tanaman itu …
“So/therefore”: use jadi or makanya: Tanaman itu tumbuh cepat …, jadi/makanya besok saya menanam tomat lagi.
Formal writing sometimes uses karena … maka …, but many style guides treat the pairing as redundant.

Can I reverse the clause order?

Yes. Putting the reason first emphasizes the cause: Karena tanaman itu tumbuh cepat saat cuaca cerah, besok saya (akan) menanam tomat lagi.

Is there a nuance difference between tumbuh cepat and cepat tumbuh?

Both are correct.

tumbuh cepat = “grow quickly” (adverbial use of cepat)
cepat tumbuh = “fast-growing” or a fronted emphasis on “fast” More formal emphasis: tumbuh dengan cepat.

Should I use tumbuh or bertumbuh?

Use tumbuh in standard Indonesian. bertumbuh exists but sounds nonstandard/archaic to many Indonesians. You will, however, see the noun pertumbuhan (growth) and the set phrase tumbuh kembang (growth and development).

Which first-person pronoun fits best: saya, aku, or gue?

saya: neutral/formal; safe with strangers, at work, in writing
aku: informal/intimate; friends/family, songs
gue/gua: very informal Jakarta slang Match your audience: Besok aku nanam tomat lagi … / Besok gue nanam tomat lagi … in casual speech.

Why menanam, not tanam, menanamkan, or menanami?

menanam = to plant (something). This is the normal active verb.
tanam (bare root) appears in imperatives or certain patterns: Ayo tanam tomat! In colloquial speech people often drop the prefix from menanam and say nanam.
menanami = to plant an area with something: menanami lahan itu dengan tomat.
menanamkan = to instill (figurative): menanamkan disiplin. Not for literal planting.

Where can I place the time word besok?

Common options:

At the start: Besok saya (akan) menanam … (emphasis on time)
At the end: Saya (akan) menanam tomat lagi besok. No preposition needed; pada besok is not idiomatic.

What’s the difference between tanaman and tumbuhan?

tanaman = a plant that is planted/cultivated; fits gardening/farming. tumbuhan = plants in general (the flora). Here tanaman is the right choice.

How would a very natural casual version sound?

Examples:

Besok aku nanam tomat lagi, soalnya tanamannya cepet tumbuh kalau cuacanya cerah.
Jakarta style: Besok gue nanam tomat lagi, soalnya tanemannya cepet tumbuh kalo cuacanya cerah. Note the casual forms: aku/gue, nanam (from menanam), cepet, kalo.

Any quick pronunciation tips?

c = “ch”: cerah → “che-rah” (r is tapped/trilled).
The e in cepat/karena is the schwa-like “uh” sound.
Final t in cepat/tomat is a crisp unreleased [t].
All a’s are “ah”: tanaman → “ta-na-man.”