Plant library · Vegetables
Allium cepa
Bulb onion is a compact annual vegetable grown for a midsummer-to-late-summer harvest. At roughly 2 feet tall, its upright leaves can sit behind very low crops without taking over the bed. Give each planting block a sunny position with loose soil, and choose a short-, intermediate-, or long-day type suited to your latitude before assigning space in the plan.
Use onions as a dense, low-footprint crop in a dedicated bed, along a sunny bed edge, or in short repeated rows that are easy to weed and harvest. Keep the planting area close to a path or open bed edge so you can reach the narrow spaces between plants without stepping on the soil. Carrots, lettuce, cabbage, tomatoes, and strawberries can be included elsewhere in the same mixed garden plan; keep beans and peas in a separate block.
Set bulb onions about 4 inches apart, center to center. Their mature spread can reach about 6 inches, so treat this as a close-planted harvest crop rather than a row to walk through. Build access around the outside of the onion block, and avoid placing taller, sprawling plants where they will crowd its light or make routine weeding difficult. Leave roughly 12 to 18 inches between rows when using conventional rows, or arrange the same close spacing in a reachable bed block.[1]
Reserve full sun for the onion bed. Loose, fertile, well-drained soil makes a practical planting zone, especially where bulbs need room to expand at the surface. Keep moisture regular through active growth rather than allowing repeated dry spells; onions have shallow roots, so a bed near a convenient water source is easier to manage. Avoid sites that remain waterlogged after rain or irrigation.[2][3]
Onions are a long-season crop, taking about 110 days to maturity and occupying their space through much of the growing season. Bulbing begins in response to day length, so the day-length class must match the garden’s latitude. Plan the bed for harvest from midsummer into late summer, then release that space for a following crop once bulbs are lifted.[1][4]
Do not use a hardiness-zone range to decide where this annual crop belongs. Instead, match the onion type to local day length and reserve a consistently sunny, accessible bed for the full growing period. Keep the dense planting clear of sprawling neighbors and maintain a workable edge for harvest.[1][4]
Editorial content updated 2026-07-20.