Spring Onion - White Lisbon This variety produces mild, tasty, white bulbs with dark green stems. It is quick and easy to grow, and perfect for salads and stir fries. Sow outdoors thinly, from March to July, where they are to crop, 1.5cm deep, directly into finely-prepared, well-dug, fertile soil, which has already been watered. Allow 15cm between rows. Seedlings usually appear in 14-21 days. No thinning is required, but keep well-watered in dry spells. Regular sowings, made every three weeks, will ensure a continuous supply through the summer. Harvest from March to October.