Potent Rageplant (3.5e Feat)
From D&D Wiki
 Potent Rageplant [Jigyousho]
Through manipulation of both your own body cells and those of the plant, you have created a better strain of the rageplant that responds better to your system.
Benefit: You have the effect of a barbarian’s greater rage (+6 Strength, +6 Constitution, same drawbacks) when using the rageplant, which now lasts for 1d6+1 rounds. The exhaustion effect still applies.
Normal: Your rageplant only gives you the effects of a normal barbarian rage and lasts for 1d4+1 rounds.