WHEN TO SOW April WHERE TO SOW Soak seeds in warm water for 24 hours before sowing in pots or trays in greenhouse at 20 degrees C WHEN TO TRANSPLANT When seedlings are large enough to handle, prick off into 8cm pots, place outside for the growing season. Move into a greenhouse or cold frame for the winter. The following spring plant out into trenches 20cm deep and 30cm wide ready for cutting the following June.