I am working on one particular region in a conworld that has a particularly cool, mild, and wet climate, similar to the west coasts of Southern Chile, New Zealand's South Island, or Washington state. So, essentially, very low annual temperature variation, with average monthly temperatures mostly between 5 and 15 C, lots of cloud cover, and prodigious amounts of rain (thanks to coastal range of high mountains), upwards of 2 to 3 meters annually with no real dry season.
I have difficulty finding resources on this because:
I'd like information about the kind of practices that a pre-modern culture could have used, and there was not that much agriculture to my knowledge in those Earth-analogue places before very recent times.
Even now that people do grow some (modern) crops in those regions, there is still very little agricultural production, certainly not for subsistence, since those regions in our world are generally sparsely settled temperate rainforest or areas used actively for forestry.
Scotland (coastal Western Highlands only) is somewhat comparable, but its mountains are lower, and it is generally colder compared to my exact comparison regions (Quinault, Chaitén, etc). In general I find there isn't much material on agricultural capacity that directly talks about climatic requirements of crops- maybe it is assumed?
So really I am just interested in anything you may know about what kind of agricultural crops and practices can be used effectively in this sort of region. I can provide any more details if necessary. Thanks.
Soil addendum: I know that soil is a very important variable for plant growth, so I have written a little about the typical soil here at the bottom for those interested- the soil would be developed on primarily mafic rock, but it has been heavily altered recently by repeated cycles of glaciation so I imagine it is relatively undeveloped. Furthermore, I know that the high rainfall will have major effects on the kind of soil here and may leach away minerals. Perhaps in certain restricted areas, peat soil will develop, but correct me if I'm wrong about that.