Here's today's harvest from the same plants:

You can't really tell, but some of the berries in the bowl are huge! They're as big as some regular strawberries. I think the ones among these in the bowl that I mean are the biggest alpine strawberries I've had, yet.
I think the key to getting bigger ones is growing them in the shade for multiple years, splitting them up in the fall (no more than one plant per spot), and keeping them wet enough. The soil they're in stays wet for a while; I really like that clay-type soil.
Location: SW Idaho, USA
Climate:
BSk
USDA hardiness zone: 6
Elevation: 2,260 feet
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