Learn Turkish: Yasemin ve lavantayı harmanlamadan edemedi. - She could not help but blend jasmine and lavender.

The word harmanlamadan uses the negative converb -madan meaning "without blending", while edemedi means "she could not do/manage". Literally, this double negative means "she could not do without blending." In Turkish, this structure (-mAdAn edememek) is the standard way to express that someone could not resist or could not help but do something.

Why does only "lavantayı" have the accusative case ending, while "yasemin" does not?

When you have multiple specific direct objects connected by ve (and), Turkish typically attaches the accusative case marker only to the last noun in the group. Here, the -yı on lavantayı applies to both the jasmine and the lavender, showing they are both specific objects of the verb.

Could I use "duramadı" instead of "edemedi" in this sentence?

Yes, absolutely. You can say harmanlamadan duramadı (literally: she could not stay/stand without blending) and it means the exact same thing. Both edememek and duramamak pair with the -mAdAn ending to express a psychological inability to resist doing something.

Is the verb "harmanlamak" only used for physical things like plants and teas?

While harmanlamak (to blend, mix, or synthesize) is very common for physical mixtures like teas, spices, and perfumes, you can also use it for abstract things. For example, as your Turkish improves you will often see it used to describe blending different musical styles, cultural traditions, or ideas.