Blackberries come from a blackberry plant.
The only time I've heard the word "bramble" was in a little song in the MST3K episode, "Werewolf." There was no relevant context from which to ascertain its meaning.
Honeybees seem to get a lot of nectar from clovers because the plants, at least back home, are everywhere.
Potato blight affecting tomatoes - I don't like gardening. My parents like to do that; they tried to introduce me to it when I was younger, but I hated being outside. Too hot, too humid, and too many blood-thirsty insects that didn't seem to care that I was using insect repellent.
Rhododendron - it was something I was never given the ok to eat when I was little, so I never pressed the matter.