Onion Growing Guide

Onion

Crop Rotation Group

Allium (Onion family) 

Soil

Fertile, well drained soil with compost dug in. In clay soil, grow in raised beds or rows.

Position

Full sun.

Frost tolerant

Yes.

Feeding

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.

Companions

Beet, Chamomile, Carrot, Lettuce, Strawberry, Tomato, Garlic, Scallions and Cabbage.

Spacing

Single Plants: 5" (15cm) each way (minimum)
Rows: 3" (10cm) with 7" (20cm) row gap (minimum)

Sow and Plant

If you don't start your own seeds, set out sets (small dormant bulbs) or pencil-size seedlings in spring, while the soil is still cool.
Our Garden Planner can produce a personalized calendar of when to sow, plant and harvest for your area.

Notes

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.

Harvesting

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.

Troubleshooting

Weed early and often to keep onions growing strong. Seedlings are less likely to bolt (produce flowers) compared to bulb onions grown from sets.

Planting and Harvesting Calendar

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