Spring onions, also called salad onions or scallions, take up little space, and help repel pests too. They are an ideal crop for polytunnel and can enliven your salads throughout the growing season. Several sowings a year will ensure a plentiful supply for salads, stir fries and sandwiches from spring right through to autumn.
Spring onions are easy to grow and can usually be harvested in as little as two months from sowing. If you fancy a continuous supply, sow seeds in single rows every couple of weeks in the ground in your polytunnel or in raised beds or small containers. Begin sowing seeds inside in early March and then sow directly all through the warmest months. Seeds sown in August or September will overwinter and provide you with a useful harvest in the spring. For seeds sown for overwintering, be sure to choose a seed variety that is suitable for late planting.
One of the biggest dangers with spring onions is accidentally weeding them out before they get a chance to grow. It is easy to mistake a spring onion for a blade of grass, which is why it is best to plant them in rows rather than scattering randomly. It is important to weed carefully and regularly around your spring onions as, like other alliums, they do not like too much competition.
While thinning your spring onions is not strictly necessary, it is best to make sure that your plants are not touching and that each one has space to breathe. Overcrowding can cause problems with downy mildew, as can watering from above. Try to avoid overhead watering and keep soil moist. A good quality organic mulch will work well to retain soil moisture and keep down weeds.
Spring onions are a great companion crop for a wide range of other plants. Carrots and other members of that family will do well next to spring onions, which, like other alliums, can confuse or repel common pests.
Lift your spring onions for use as needed, while they are still young and the bulb (if any) is still small. You can use the spring onions in salads or finely chopped as a garnish on a range of dishes. To increase your yield and truly make the most of your spring onion crop, you can also choose to use all but the root and base of a spring onion. The rooted base section, placed in water which is refreshed every day, will regrow a new upper green portion, so you get a second harvest.