Why won’t the hibiscus bushes flower

Mosquito bites aren't "harmful" as the game has no HP system and you cant die or anything like that.

However, as stated by Alex, it prevents you from catching them. Residents may also have a new dialogue with you. Getting bitten by one also attracts more of them (creating an annoying cycle of stings)

You can avoid mosquitos rather easily, they have a short 'aggro' range and you can hear them coming (high pitched buzzing). They are also very slow moving, so they are easy to catch (once you spot them that is).

In short, they are just annoying. They only appear Summer evenings, though, so be a bit more careful during this timeslot.

Okay, so I did a few experiments in the past few days, and I will post what I found and what I didn't. For reference, when I say "adjacent tiles" I mean the three tiles above, the three tiles below and the two tiles on each side of the bush.

• You can plant bushes alone in the village. By that I mean that you can plant bushes anywhere in the main village if all its adjacent tiles are free.
• You cannot plant bushes on the beach. The two attempts at doing so have failed, so I conclude that it can't be done.
• You can plant bushes next to each other. I've attempted to plant a row of bushes, as well as three bushes in an L pattern, and both attempts succeeded. I don't know if you can plant a square of bushes (4 or 9 or + bushes), but I have no reason to think you cannot. I didn't do the test because I ran out of bushes, but if I can I'll test this and update this answer.
• You can plant bushes next to a tree. An attempt at planting a bush right next to a tree succeeded, so I conclude that it can be done.
• You cannot plant bushes adjacent to a river tile. I planted a bush next to a straight river going North-South, and it wouldn't grow.
• You cannot plant bushes adjacent to a cliff. Self-explanatory.
• You cannot plant bushes adjacent to a building or a public works project. In my opinion this is the most important test. I planted a bush at the following four locations: next to my house, next to Re-Tail's, directly above a lamppost and above-left the same lamppost (so left of the previous bush). All of these wilted. My conclusion is that you cannot plant bushes adjacent to a building or a public works project.
  Note: This last test cost me upwards 40'000 bells and 4 days to build/remove the lamppost and obtain the bushes. I strongly advise against attempting to reproduce this experiment due to the cost in time/money.
• Bushes can grow in a connection of 12 at most. This includes trees and stumps, vertically, horizontally, and diagonally. If a bush or a tree is planted near a sequence of twelve bushes/trees/stumps touching each other, that thirteenth sapling will not grow.

Other than these I haven't seen any limitations in where to plant bushes. Obviously since you need to dig a hole in order to plant a bush, you cannot plant a bush anywhere you cannot dig a hole (maybe I should've added that above, but oh well).

Hope this helps!