I sowed mine at end of April in a shade house, and pricked out into 9cm (3.1/2")pots a fortnight later. Planted about end May onto allotment, quite close together, about 6" apart. I have good, deep ditches because we flood on winter, so I filled about 6ft length of ditch with muck and planted in that, then about 2" sieved clayey topsoil. It's easy to keep this really moist which is what they like. mine are about 20 - 30cm high. Self blanching though.