I hadn't realized that trees basically vanished with the dinosaurs. My understanding is that it was due to global firestorms: the original impact ejected a lot of material on ballistic trajectories that landed all over the planet, and came back very hot from the original impact (unlike an actual meteor, which has cooled to the temperature of deep space). These started fires basically everywhere.

Fortunately, unlike dinosaurs, trees left seeds that could eventually manage to germinate once recovery flora and fungi had gotten the environment back to something closer to reasonable.

And hmm...that makes a lot of sense. Though it's also possible that it was an error in my notes?