I have not done it myself, but here is what the literature says (2 bd books
and internet; I am not citing, because they are in German, without meaning
to imply that there is nothing in English on the subject)
Washtubs sunk into the soil and covered with straw or leaves
in the basement as described by Gil
outside in mild areas, where frost is not too bad, on top of the field
covered with film and straw
outside in mounds:
dig 20-25 cm trench, cover bottom with film or tight wire netting,
heap root vegetables up top 1 m high (cabbages can placed just tightly
next to each other, i.e. not heaped up, upside down root stalk sticking up
in the air), cover with a 10-20 cm thick layer of soil, on top of
that 30 cm layer of straw and another 15 cm layer of soil.
Christiane
