Lag when crops planted with custom model

Minecraft seems to lag when placing crops when the farmland has a custom block model.

Affected by

• Amount of farmland
• (= amount of GLquads?)

Not affected by

• VBO's
• Render Distance
• Game mode
• Single- or multiplayer

Steps to reproduce
1. Select a resource pack with custom model for farmland
2. /fill ~ ~ ~ ~30 ~ ~30 farmland 7
3. Place crops & enjoy lagging