Sunflowers, two-tall ferns, and two-tall grass generate but none of the other two-tall variants do in newly created worlds.
Environment
Minecraft Version: 14w06a
Operating System: Windows 8 (amd64) version 6.2
Java Version: 1.7.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 200651224 bytes (191 MB) / 704380928 bytes (671 MB) up to 954466304 bytes (910 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Launched Version: 14w06a
LWJGL: 2.9.1
OpenGL: AMD Radeon HD 8450G GL version 4.2.12422
Duplicate of MC-45554