I would like to use the passive form in describing the fact that a flower has been watered.
Is この花は水をやられた correct? What difference does この花は水がやられた make or would that be incorrect?
A brief explanation of the use of が in passive phrases would also be appreciated.
We would say neither:
「この花は水をやられた。」
nor
「この花は水がやられた。」
for two reasons. These "sentences" sound far more unnatural and awkward to native speakers than you could probably imagine.
Reason 1:
While the "grammatical" passive-voice form of 「やる」 is certainly 「やられる」, the latter generally has a fairly negative connotation. "To have something undesirable done (to you)" is the usual meaning/nuance of 「やられる」.
Reason 2:
Inanimate subject -- 「この花」. It is not nearly as common in Japanese as it is in English. Japanese-learners tend to use the inanimate subject in Japanese because they tend to translate directly from their native languages.
Thus, while "This flower was watered." is a perfectly natural English sentence, its literal counterpart 「この花は水をやられた。」 is not a sentence native Japanese-speakers would ever form under normal circumstances. It is that off. It sounds as if it were a big mistake to water that particular plant.
So, how would we say "This flower was watered."? I would use the unmentioned "I" and say:
「この花には（もう）水がやってある。」 or
「この花には（もう）水をやりました。」
Notice both are in active-voice. The passive-voice simply would not work here unless you wanted a stiff, wordy and unnatural sentence like:
「この花はすでに水を与{あた}えられています。」
You would sound like a robot (or Google Translate) if you said that.
A brief explanation of the use of が in passive phrases would also be appreciated.
This is what I take you to be talking about.
「Aは + Bが + [passive-voice verb]」
means:
"As for A, B has been ~~." ← B is part of A.
You can say things like:
「私は肝臓{かんぞう}がやられている。」 = "As for me, my liver is damaged."
↑ That is how you use 「やられる」.
「Aさんの家は、台風{たいふう}で屋根{やね}が吹{ふ}き飛{と}ばされてしまった。」 = "As for A's house, its roof has been blown off by the typhoon."
You should say この花には水がやってある or この花は水がやってある.
But この花は水をやられた and この花は水がやられた may be grammatically correct.
この花は水がやられた may sound like another flower may be poured a kind of liquid apart from water to.
私は腕を掴まれた。
私は腕が掴まれた。
Both mean “My arm was caught.” But second one sounds like Another one’s leg or hand may have been caught.
