Fertile, well drained soil with compost dug in. In clay soil, grow in raised beds or rows.
Mix a balanced organic fertilizer into the bed or row before planting your onions, taking care to get it into the soil below the plants. Do not feed plants that are nearing maturity if you want very sweet onions.
Beet, Carrot, Cabbage, Chinese Cabbage and Swiss Chard.
Single Plants: 5″ (15cm) each way (minimum)
Rows: 5″ (15cm) with 9″ (25cm) row gap (minimum)
Sow and Plant
If you don’t start your own seeds, set out sets in fall when the soil is cool. Japanese bunching onions are often planted in the fall in cooler climates.
Onions respond to changing day length. Grow short-day varieties in southern latitudes. Long-day varieties work best in northern areas. Try growing different varieties from seed to explore differences in bulb color, size and shape.
Harvest young onions as scallions. When bulbs form and the tops of the plants fall over, pull them and cure in a warm place for about 10 days before storing.
Weed early and often to keep onions growing strong. Seedlings are less likely to bolt (produce flowers) compared to bulb onions grown from sets.