Mustard - White This variety is quick and easy to grow, a favourite salad garnish that can be sown all year round, and even outside. Sow indoors all year round by sprinkling seed on moist kitchen paper, cotton wool, or a thin layer of seed compost. Cover with kitchen paper until seeds start to geminate, then remove. Keep moist, do not allow to dry out. Cut with scissors when about 5cm tall. Sowing to harvest takes up to 14 days. Regular sowings, made every two weeks, will ensure a continuous supply. Mustard can be sown outdoors in a seedbed in summer. It will produce larger, hotter leaves. Harvest all year round.