[quote=@Zarkun]
<Snipped quote by Zarkun>

*cough*
[/quote]

Not always. It's random.

[quote=@Burthstone]
Two questions, one needs a houseruling (Probably)

1. Does a person still have stored magic power if they don't eat a berry?

2. Did Joshua eat a berry?
[/quote]

Yup, because magic is still able to be sucked out of them.