How much Haste I need to get 1s on Regrowth?

Hello,

I currently have 1000 haste rating on my Resto Druid and my Regrowth is still on a 1.4s cast time as well as Nourish which is at 1.1s.

I've seen some streamers that did have Regrowth on 1s cast time and Nourish on like 0.6 or even 0.5 seconds.

What is the haste cap on Resto Druid and what would I need in order to get what I want?

Thanks for the help gang!

Are you sure those streamers didn't have Hero or something like that on? I don't think it's possible to cut cast time that much with haste

Hero/Blood lust + potion of speed + other buffs.

Considering GCD is 1s, no need to push spells below 1s cast time?