Onion (Red) Growing Guide Allium cepa Crop Rotation Group Allium (Onion family) ● Soil Fertile, well-drained soil enriched with compost. Position Sun or partial shade. Frost tolerant Yes. Feeding Not normally required, though overwintered plants can be given a liquid feed in spring. Spacing Single Plants: 15cm (5") each way (minimum) Rows: 10cm (3") with 20cm (7") row gap (minimum) Sow and Plant Start seeds in pots under cover in late winter before planting out in mid to late spring, or grow from purchased sets (immature bulbs) planted in mid to late spring. Our Garden Planner can produce a personalized calendar of when to sow, plant and harvest for your area. Notes Harvesting Harvest as soon as they reach a reasonable size. If storing them, wait until the tops start to die down and dry for about 10 days. Troubleshooting Weed early and often to keep onions growing strong. Planting and Harvesting Calendar < Back to All Plants Pests which Affect Onion (Red) Allium Leaf Miner Aphids (General) Millipede Onion Root Fly Slug Snail Plant Diseases which Affect Onion (Red) Allium White Rot Onion Downy Mildew Onion Fusarium Basal Rot