That would be your fault. You had a single vehicle accident, and single vehicle accidents are always (always) blamed on the only vehicle involved. It's never a question for debate, not even in a country as famous as yours for lengthy and wordy debates. (Sorry, couldn't resist. You used too much English English for me to avoid it.)
If you had hit the truck, it might have maybe possibly been 50% the other vehicle's fault. Maybe more, in fact. But you didn't hit the truck, you hit the weeds. Since it can't be the fault of the weeds, not even if they were in the middle of the road, that kind of narrows it down.
But since specific words do matter, let's use the proper word. It wasn't your fault per se, because you really did nothing wrong. You had a choice between driving into the ditch and becoming a hood ornament on a larger vehicle, so you did the right thing. You did what any reasonable and prudent person would do in that situation. But you are legally responsible for the damage, both to your car and to the hedge, because that's how it works when you own a car. You agreed to that responsibility when you purchased the vehicle, in fact.