the meaning of "thick" [closed]

Feral horses, belonging to my grandfather, ran wild over thick banks of water hemlock, and there were more than a few rattlesnakes.
_{Educated: A Memoir by Tara Westover}

I was told it is like "thick forest", so thick does not modify banks even it is "thick banks of".

He was standing at the head of the table; the rest of us perched on benches, studying the thick planks of red oak.
_ibid

Here, I think thick is for planks

So, my question would be in the form of "the thick A of B", which one does thick modify, A or B?

Solution 1:

Thick banks of water hemlock

To me this conjures a picture of exuberant collections of water hemlock appearing to form islands or banks within a marshy field.

Remember that water hemlock, Cicuta virosa, likes to grow in wet grassland, sometimes called "water meadow".

It is implausible that wild horses would be making a special point of running along the very edge of a river. It is more plausible that they were running through wet grasslands / water meadow, such as that shown above, and that the "banks" were not edges of a river, but rather random clusters of water hemlock.

Solution 2:

Regarding the question :
... "the thick A of B", which one does thick modify, A or B?

Option A because I interpret your examples as :

• the thick (i.e. dense) banks [of flowers]

• the thick (i.e. several cm wide) planks [of red oak]

Perhaps the confusion is that thick has multiple meanings. In second sentence I’d interpret it as :

growing close together and in large amounts:
thick forest.
thick, dark hair.
— cambridge.org

Likewise, bank has various meanings, and I read it here as

bank noun (3) : a group or series of objects arranged together in a row or a tier.
a bank of vending machines — merriam-webster.com