1. What are these little white scaly things on my dogwood and what should I...
We only got a photo for the St. John's wort and answered that separately.
Dogwoods can get a scale insect problem. However, we can't say, without a close-up photo, what type of scale it has. We need to identify the scale in order to give you correct control information for that species. Please send us a close-up photo and/or put "dogwood scale" in a search engine and see what looks like what is on your tree, then let us know.
Unfortunately, we cannot see the necessary identifying details from your photograph. If they move, they could be apple mealybugs or Taxus mealybugs.
You could lift one off the leaf and see what is underneath it. Scale insects cover themselves with the outer material and if they are scale insects you will find either a dead scale insect or perhaps an egg mass.
We can't recommend a treatment until we can identify the insect. Simply pick them off by hand if practical.