Symptom - Growing bamboo within a chunk causes lag within a radius of the chunk where the bamboo is located.  If inside the radius then there's a very noticeable lag spike every time bamboo is growing.  If outside the radius then there's no lag spike at all while the bamboo is growing.

How to duplicate - Create a flat peaceful world.  Plant bamboo on every block within a single chunk.  Wait for the bamboo to grow and you'll notice lag spikes as the bamboo gets taller.  Crouch-walk away from the growing bamboo and find the block under you where the lag completely stops, and place a block on the ground.  Continue testing the area around the bamboo until you've drawn a border where the lag is noticeable, and you'll draw a circle.

Pictures:

bamboo_range = x/z radius where lag is evident.

bamboo_outside = if player is outside of the circle, there's no bamboo lag.

bamboo_inside = if player is inside the circle, there's lag spikes when bamboo is growing.

bamboo_oborder = if a block is updated outside of the chunk border where the bamboo is located then there will be no lag.

bamboo_iborder = if a block is updated on or inside of the chunk border where the bamboo is located then there will be a lag spike.

Other observations - The circular range also follows the 'y' axis, so the lag range is spherical rather than circular.  I haven't yet tested this lag issue with other plants besides bamboo.