I'm using Minecraft 1.9.4 with Forge and liteloader and several other mods.
I've crafted the Lexicon and the pestle and mortar but there isn't one flower to be seen anywhere.
I also have Quark which I downloaded because I was getting a message ingame saying to migrate to vanilla or quark.
I have no idea why there are no flowers.
Forgot to mention that I have the very latest Botania download v310

the spawn rate got lowered in one of the final 1.7 versions. It seems to be fine for me and everyone else. Do you have any worldgen mods?

No other world gen.
However, I found out that if I started a new world everything was great, but my interest was in my current world, and at one point I was exploring and found out that when I went to unexplored parts of my world the flowers started showing up. So I have nothing by my area but at least I can go further afield to get them

Yes, the flowers do not retrogenerate.

So this is resolved

Did you add Botania after starting the World?