Spring onions (Allium cepa Aggregatum Group) are part of the large onion family (Alliaceae) but are much quicker and easier to grow than onions. They have pencil-thick green, onion-flavoured hollow leaves with white bases and are also known as shallots (the name used in supermarkets), scallions, green onions and bunching onions. A popular variety is ‘Straight Leaf’.

Spring onions are sweeter and milder in flavour than onions. They add a gentle onion flavour to foods. Spring onions are used fresh mainly as a garnish for salads but also added to hot dishes such as stews or soups and team very well with eggs. Spring onions can be substituted for leeks. They are low in calories but high in fibre, vitamins A, C, B2 and thiamine and many minerals.

Follow our seven easy steps to successful spring onion harvest including tips along the way.

When to plant

Spring onions can be grown throughout the year in most locations.  Check with hardware and garden centres for advice on varieties to grow in your local area.

1. In subtropical and tropical areas, sow or plant year-round.
2. In cool and temperate areas, spring onions are best sown or planted from spring to autumn.
3. If growing in winter in warmer temperate areas, move indoors on days of frost or cooler temperatures.

Location

• Plant in a full sun position in soil that holds moisture well.
• Too much shade, especially as days shorten in winter, can cause spring onions to become spindly with thin stems that may be prone to pests such as aphids.
• They can also be grown in containers if space is limited, using a good quality potting mix.
• Spring onions can be used to repel some pests due to the strong odor they may give off.

Soil

Get the soil right to harvest a bumper crop of spring onions.

Follow our steps for easy soil preparation.

• Spring onions prefer a neutral to slightly alkaline soil so adding lime before planting is beneficial and ensures good growth where soils are highly acidic.
• Dig in extra well-rotted organic matter such as compost, well-rotted manure and/or Seasol Super Compost to a depth of 30cm before planting.
• A soil rich in nutrients helps build strong plants, so add Seasol Plant + Soil Booster (100g per square metre) and a fertiliser such as PowerFeed Controlled Release for Tomatoes & Vegetables.
• Water in well and let the soil rest for a week or two.

Step 1 – Sowing seeds

• Grow from seed sown directly in well-prepared, moist soil at a depth of 5-6mm. Space seeds 7-10cm apart in rows around 15-20cm apart (for ease of weed control). For a constant supply, sow seeds every four to six weeks
• Alternatively, sow seeds into shallow rows in punnets or seed trays filled with a premium seed raising mix such as Seasol Seed Raising & Cutting Potting Mix. Once the seeds are sowing lightly cover them with seed raising mix.
• Water in well with Seasol GOLD or Seasol (mix 30mL concentrate per 9 litres of water – standard watering can) as this will help to increase seed germination rates.

Step 2 – Germination

• Expect germination in 10-14 days (although it may be slower in very hot or cold conditions). Watch for the tiny leaves to come through the soil.
• Soil should be moist but not wet. Too much water and the seeds may rot. Check soil moisture daily and water gently when dry for good growth.
• Protect emerging seedlings from snails and slugs and watch out for aphids (gently hose off).
• In the ground, thin overcrowded seedlings to 7-10cm apart. Use scissors or tweezers when thinning seedlings to avoid root damage.

Step 3 – Baby spring onion seedlings

• Thin the spring onion seedlings out again 2-3 weeks later to around 10-15cms, so they are not competing for nutrients and space.
• Keep your young seedlings moist but not wet. On days of extreme heat, check young seedlings morning and night.
• Apply Seasol or Seasol GOLD weekly to stimulate healthy growth and good root development.
• Apply a liquid fertiliser regularly every fortnight such as PowerFeed PRO SERIES for Tomatoes & Vegetables for a bumper crop.

Step 4 – Planting out spring onion seedlings

• Transplant punnet-grown seedlings when they are large enough to handle at around 10cm high. Soak punnets to make it easier to separate the fine seedlings.
• Plant 7-10cm apart and firm into the ground or lay seedlings in shallow rows around 6mm deep.
• Just cover the roots so the plants are stable but not buried. Watering washes soil in around the stem with Seasol or Seasol GOLD to aid plant establishment.
• If transplanting purchased seedling, plant in the same way as above, following the directions on the plant tag.

Step 5 – Spring onion plant growth

• As spring onions grow, keep the soil around the developing plants hand weeded or gently hoed and well-watered. Spread a light organic mulch around each row to suppress weeds and keep the soil moist.
• Liquid feed to encourage fast, healthy, tall growth using PowerFeed PRO SERIES for Tomatoes & Vegetables applied fortnightly. For young plants mix 20mL of concentrate per 9 litres of water – standard watering can. As plants mature, increase rates to 50mL of concentrate per 9 litres of water.
• Continue to water regularly in hot weather and cover with a shade cloth to provide protection from the afternoon sun.

Step 6 – Ongoing spring onion plant care

• Every 6-8 weeks, apply another application of PowerFeed Controlled Release for Tomatoes & Vegetables to produce a bumper crop
• Check soil moisture every day especially during times of high heat and for plants in containers. Take care not to overwater soil as this could lead to diseases like downy mildew.
• On days of high heat move container plants to a cooler location, such as underneath a tree.
• Continue to remove weeds as they compete for water and nutrients and top up mulch as required. Take care with removing weeds not to disturb the plant’s roots.

Step 7 – Spring onion harvest

• Spring onions leaves can be cut early for cooking, especially for use as a garnish.
• Harvest the whole spring onion plant when plants are pencil thick, around 15-20cm tall, and have a small bulb. This is usually around 8-12 weeks from planting.
•  Simply, pull as needed from the soil using your hands or use a hand fork or trowel if needed.
• Wash well and use immediately, or store for several weeks wrapped in plastic in the fridge.

Things to watch for..

Well grown, spring onions have few pest problems. Diseases are generally kept at bay by correct spacing at planting and keeping the growing area weed free. Some problems that can occur include:

• Aphids These tiny black or green pests cluster under leaves. Squash or hose off.
• Onion thrips Minute insects that cause white flecking on the leaves. Remove worst affect leaves and increase watering to compensate for feeding damage.
• Slugs and snails These pests can destroy young plants. Snails and slugs are active at night; squash those that are seen. Use iron-based, non-toxic baits to control these pests.