What. A. Grow. :)
I'm also in the northern hemisphere (51° N, Köppen Cfb, USDA 9b) and I've always 50% of this yield outdoors.... but then again I hardly read books on the subject & never used 60 l pots before :*0
This year is the first year I'm growing 100% indoors. 100% so I can speed up the learning curve.
Did she grow in a greenhouse or under the naked sky? Might find out in a few minutes when I check every week, but as mentioned before, I can be a bit lazy at times....
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