Lag when fancy graphics is on

I was ready to play PvP on a server. But before that, I usually create a world to let the server load up. However, when I was playing the world, lag occurred near a biome with leaves.

When I expected to happen was there will be 0% lag when in a plains or biome with leaves when I have fancy graphics on.

However, it caused a lot of lag to me even though I'm not using a low-end device. And for more serious cases like when I am playing on my LP (Generated in a taiga biome), it leads to a crash.

Steps to reproduce:
1. Go into a world with leaves. (Must have fancy graphics on)
2. Run around and you will find lag.