I FOUND IT! 3420 is the Perception you want for your MIN/BTN retainers!

[Roth_Trailfinder]

I am probably going to wait until the final gear set to upgrade my retainer gear beyond the MH and OH tools. But it would be interesting to know how much Perception is needed to get 50 Alien Onion per venture.

[Silverbane]

But it would be interesting to know how much Perception is needed to get 50 Alien Onion per venture.

4104 Perception for 50 Alien Onions per venture.
3762 to get 40.

[Silverbane]

4104 Perception for 50 Alien Onions per venture.
3762 to get 40.

BTW, these numbers were not determined experimentally, but were taken from the Garland Tools database:

https://www.garlandtools.org/db/#item/36097

There you can find the yield-vs-perception data in the "Ventures" section of "Sources and Uses" for an item, if that item can be obtained via a mining or botany venture.

The maximum perception possible in the current best gathering gear is 3874 (without food), so at present, it is impossible to get 50 Alien onions from one venture.