How can transitive and passive be combined in 茎を編んで作られる?


In the following sentence, taken from an article about tatami the transitive
and passive verbs (編む＆作る）seem to be combined into one phrase to express what I
have said translation but it does not seem to fit any logical grammatical
sequence:

> 畳表というのは、畳の表面、つまり人の足が触れる部分で、ここは、イグサという植物の茎を編んで作られています。
>
> Tatami-omote is the surface of the tatami mat, in other words the part that
> comes into contact with people's feet. It is made from rushes woven
> together.

I assume the Japanese (if not my translation) is correct but can somebody
explain the logic of what is being described grammatically?

My best guess is that the passive verb （作られている） is somehow acting on the
transitive (編んで） in the same way that ある acts on transitive verbs in
expressions such as 「ご飯を作ってあります」(note) but it is my first time to see this and
I don't recall it in any text book.

Note: を was chosen deliberately in this example to be consistent with my
subject sentence.




I think イグサという植物の茎を編んで is an adjunct that tells us _how_ the main clause verb
作られています happens. That is, it's similar to the English:

> _tatami-omote_ is made [by weaving rush stalks]

Note that the English has one passive ( _is made_ ) and one non-finite verb (
_weaving_ ). It corresponds fairly well to the Japanese, in which 作られている is
passive and 編んで is non-finite. There's no need for the other verb to be
passive, just like in English _weaving_ doesn't need to be passive.




I think イグサという植物の茎を編んで is an adjunct that tells us _how_ the main clause verb
作られています happens. That is, it's similar to the English:

> _tatami-omote_ is made [by weaving rush stalks]

Note that the English has one passive ( _is made_ ) and one non-finite verb (
_weaving_ ). It corresponds fairly well to the Japanese, in which 作られている is
passive and 編んで is non-finite. There's no need for the other verb to be
passive, just like in English _weaving_ doesn't need to be passive.

