Druid talent · row 6 of Restoration, from level 35 (30 with Talented 5/5) · Physical

Improved Regrowth Rank 1

Improved RegrowthRank 1

Increases the critical effect chance of your Regrowth spell by 10/20/30/40/50%.

Game files · build 1.60.1.70245Read from the WoW Forever beta client, build 1.60.1.70245.

Compared with Classic

Classic tooltip

Increases the critical effect chance of your Regrowth spell by 10%.

What Blizzard said about Improved Regrowth, each line checked against the files.

Matches the files
Improved Regrowth: Now requires Improved Rejuvenation as a pre-requisite.
The files Improved Regrowth (17074) requires Improved Rejuvenation in the 70245 tree; Classic Era had no prerequisite.
Improved Regrowth Improved Rejuvenation Class deep dives: Hunter and Druid

69876 Sep 16First beta build we archived. No changes in the client files since.