Can Onions Be Grown in an Indoor Garden?

Pots and Containers

• Onions are root crops and require adequate depth and width in their pots. Use 5-gallon pots, containers, barrels or tubs with drainage holes for onion plantings, and choose from clay, plastic, stone or wood materials. Onions do not take up large amounts of surface space, but do require at least six to 10 inches of depth.

Potting Soil and Fertilizer

• Onions do best in loose, moist and nutritious soil and require additional moisture retention in dryer indoor environments. Ohio State University recommends using commercial mixes or building your own foundation with equal parts peat moss, organic compost, potting soil and vermiculite. Mix 5-10-10 or 8-16-16 fertilizer into the potting soil for added starting nutrition.

Planting

• Plant onion seeds 1/2 inch deep at variety-specific distances. Most onions do well with three inches of space for growing. Plant multiple seeds in larger pots for grouped plantings, and label each planting site or pot to track onion variety for harvest.

Maintenance Care

• Keep the indoor onion garden in spots with full sun or artificial light and good air circulation. Onions thrive with cool 60- to 70-degree temperatures for rooting and establishment and 75-degree temperatures during bulb growth. Water onions with two inches of water whenever the soil dries to keep them moist. The University of Minnesota Extension notes that onions can't grow properly without adequate moisture. Harvest green onions when they reach desired size and all other onions when the tops dry and fall over.