uekibati no mizuukezara, zyouro, kirihuki wo zyunbisita.

Normally, it would be written without spaces:

植木鉢の水受け皿、じょうろ、霧吹きを準備した。

The spaces in your version are just there to make it easier for learners to see the parts.

It is most naturally understood as one item: the saucer / drip tray for a flowerpot.

So the full list has three things:

• 植木鉢の水受け皿
• じょうろ
• 霧吹き

If you wanted to say flowerpot and saucer as two separate items, you would normally say something like 植木鉢と水受け皿.

Here, の links two nouns.

植木鉢の水受け皿 means something like:

• the water-catching saucer for a flowerpot
• the flowerpot’s saucer

This の does not have to mean strict ownership. It often shows a broad relationship such as:

• possession
• category
• purpose
• connection

So here it is better understood as the saucer associated with / used for a flowerpot.

Because を marks the whole list as the object of 準備した.

Japanese often puts the particle after the entire list, not after each item:

A、B、Cを準備した。

This is very normal.

You could repeat を after each item in some cases, but that would usually sound more marked or emphatic.

Using 、 makes this sound like a simple written list: very natural in notes, descriptions, inventories, or straightforward narration.

So:

植木鉢の水受け皿、じょうろ、霧吹きを準備した。

feels a bit like listing items one by one.

If you used と, it would sound more like a tightly grouped list:

植木鉢の水受け皿とじょうろと霧吹きを準備した。

That is also grammatical, but the comma-list style is often smoother in writing, especially when the items are just being enumerated.

準備した is the plain past form of 準備する.

• 準備する = to prepare
• 準備した = prepared / got ready

So this sentence is talking about something that was done in the past.

If you wanted the polite form, it would be:

準備しました

It means they prepared / got them ready, not that they manufactured them.

In this sentence, 準備した suggests something like:

• gathered them
• set them out
• made them ready for use

So the idea is that the person got the saucer, watering can, and spray bottle ready.

The subject is omitted.

That is extremely common in Japanese. If the context already makes it clear, Japanese often leaves out words like:

• I
• we
• someone

So depending on context, this could mean:

• I prepared them.
• We prepared them.
• Someone prepared them.

Japanese very often relies on context instead of stating the subject directly.

This is a normal feature of Japanese writing.

• 植木鉢 is commonly written in kanji.
• 水受け皿 is also commonly written with kanji and kana mixed.
• じょうろ is very often written in hiragana.
• 霧吹き is commonly written with kanji plus kana.

Some everyday words are often written in hiragana because that is the most familiar or readable way. So じょうろ in hiragana is very natural.

Here are the readings:

• 植木鉢 → うえきばち
• の → の
• 水受け皿 → みずうけざら
• じょうろ → じょうろ
• 霧吹き → きりふき
• を → を (pronounced お in modern Japanese)
• 準備した → じゅんびした

So the whole sentence is read:

うえきばち の みずうけざら、じょうろ、きりふきを じゅんびした。

It is a compound noun:

• 水 = water
• 受け = receiving / catching
• 皿 = plate / dish

So 水受け皿 is literally a water-catching dish, which in natural English is something like:

• saucer
• drip tray
• water tray

In this sentence, it means the dish placed under a flowerpot to catch excess water.