Do Walipini Underground Greenhouses Work in UK?

UK gardener critique arguing walipinis suited to Bolivian equatorial latitudes fail physics tests at 50–60°N due to low winter sun angle, cold-air pooling in pits, poor plastic insulation, and sparse evidence; distinguishes Victorian pineapple pits. Notes Aymara/Bolivia origin and earth-sheltered cold-frame definition via Wikipedia. Argues success likely near equator (Bolivia 16–22°) but not at UK longitudes 50–60°N where seasonal sun-angle extremes are severe. States cold air sinks so pit bottoms cool quickly toward freezing in winter/shoulder seasons despite deep-earth stability in mines/caves. Critiques circulating social-media walipini photos as showing heavy shadow and sparse vegetation; mid-December sun angle ~15° at author’s location vs ~60° midsummer.

Evidence tier: popular_guide. Opinion/gardening blog, not peer-reviewed field trial.

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