I gave my friend on my whitelisted server a flower pot using the give command. Then my friend got a flower and put it in it. He could see it, but I could not. We tested this and it works vice versa.

Steps
1. make a whitelisted server and have at least one other player on it
2. give the player a flower pot by the give command
3. place the flower pot
3. have the player place a flower in the flower pot
I could not see the flower when my friend place the flower and when i placed the flower, my could not see it.

thanks