Sweet Onion Seeds

West Coast Seeds, Sweet Onion Seeds - Additional Information

How to Grow Onions

Planting Schedule:
Sow sweet onion seeds indoors in late winter for transplanting to the garden 2-4 weeks after the last frost. For overwintering, start seeds in early summer for a mid-August transplant. Scallions can be directly seeded every 3 weeks from after the frost until late summer. Germination prefers soil temperatures of 21-25°C (70-75°F), and seedlings appear in 6-12 days.


Seed Starting:
For most home gardeners, starting seeds in trays is advisable. Plant 3 seeds around 5mm-1cm (¼-½") deep per cell in a 72-cell tray, transplanting them as a group while maintaining a 15cm (6") gap in rows that are 45-75cm (18-30") apart. For densely planting scallions, a spacing of 2-5cm (1-2") in 15cm (6") apart rows works well.


Growing:
Sweet onions thrive in a pH of 5.5-6.5, necessitating fertile, well-draining soil under full sunlight. Incorporate ample organic matter and a balanced organic fertilizer into your soil before planting. Keeping the soil consistently moist in the top layer is crucial, with the bulk of the bulb forming above ground. Remember, the size of the bulb correlates with the foliage's volume. Protect late-season scallions from frost with suitable coverings.


Harvesting:
Cease watering by early August to dry out the bulbs. Once the onion tops begin to fold, complete the process manually to start drying. Leave onions to cure the soil for a few days. Should inclement weather threaten, move onions to a sheltered, dry area away from sunlight to cure for two to four weeks. After curing, trim roots and cut stems about 2cm (1") above the bulb. Store in breathable containers in a cool, dark place, checking periodically for spoilage. Properly cured onions will last until the late spring.

Onion Pests & Diseases

Botrytis Blast:
To prevent Botrytis blast, a fungal disease that affects scallions, ensure good air circulation around your plants by spacing them properly and avoiding overcrowded conditions.

Implement a crop rotation strategy to avoid planting alliums in the same spot year after year, as this can reduce the build-up of fungal spores in the soil. Water the base of the plants early in the day, giving them time to dry before evening, to keep the foliage as dry as possible. If you detect the disease, remove and destroy affected plants to prevent its spread.

For organic control, apply a copper-based fungicide as a preventive measure during humid or wet conditions, following label directions closely.


Downy Mildew
Downy mildew, another fungal issue, thrives in cool, wet conditions. To fend off this disease:

1. Water your scallions in the morning so the plants have time to dry throughout the day.
2. Ensure proper spacing between your scallions to improve airflow and reduce humidity levels around the plants.

Use organic fungicides and follow the instructions carefully to prevent the disease from spreading. Keep the garden clean by removing plant debris after the growing season to reduce the risk of downy mildew.