If you are looking to get a spore blossom in Minecraft to add to your flower collection, you will need to start looking inside lush caves. Lush caves are a new addition to Minecraft and, as you can tell by the name, only spawn underground.
However, before we begin, please note that lush caves are not in the game but will be in part 2 of the cliffs and cave update in Minecraft or update 1.18.
That said, if you want to locate a lush cave when it gets added to the game, you can do so by first locating a Azalea tree in a grass or wooded biome.
The reason you must do this is that a lush cave will always sit underneath Azalea tres. So once you locate this tree, you will need to start your search for the lush cave by digging under it.
After a bit of digging, you should find the lush cave you are looking and a spore blossom inside of it growing. You can also grab a few glow berries and even try to tame a new mob inside the lush cave while you are there.
That being said, beyond being for decoration, spore blossoms don't have much use beyond just being a pretty flower. Nonetheless, they will still make a fine addition to your flower collection. Another thing is that these flowers grow on the bottom of dirt blocks, thus making them an interesting flower for base decoration.