Green onions, often called scallions or bunching onions, are a flavorful and versatile addition to home gardens, and starting them from seed is a straightforward, rewarding process. These slender members of the Allium family provide a continuous harvest of mild, tender greens without forming large bulbs. Successfully germinating the small, black seeds ensures a robust supply for your kitchen. This guide details the specific steps and environmental controls needed to achieve high germination rates and establish healthy seedlings.
Essential Preparations Before Sowing
Before planting, gather the correct materials to create an optimal environment for the seeds. The most suitable growing medium is a sterile, fine-textured seed-starting mix, which provides necessary drainage and aeration. Traditional garden soil is too heavy, compacts easily, and increases the risk of soil-borne diseases like damping off. Using a fresh, sterile mix helps prevent fungal issues that can devastate young seedlings.
Shallow flats or trays are better than small individual pots for starting green onion seeds. The seeds benefit from a brief period of hydration before being sown to encourage quicker sprouting. Soaking the seeds in room-temperature water for two to four hours softens their hard outer coat, speeding up germination. Plant the pre-soaked seeds immediately.
Step-by-Step Planting for Germination
Sowing green onion seeds requires attention to depth and moisture for successful emergence. Start by filling containers with the moist seed-starting mix, gently tamping it down to remove air pockets without overly compacting the soil. Sow the seeds very shallowly, ideally about one-quarter inch deep, as they need minimal resistance to reach the surface.
Green onions can be sown thickly, especially if you plan to harvest them as thin scallions or transplant them in clumps later. Gently scatter the seeds across the surface, then lightly cover them with the remaining quarter-inch of mix or a thin layer of fine vermiculite. Water the tray from the bottom by placing it in a shallow pan of water for 15 to 20 minutes until the surface moisture is visible. Use a gentle misting bottle for subsequent watering to prevent dislodging the small seeds.
Maintaining Optimal Conditions for Sprouting
Maintaining consistent environmental conditions is crucial until the first sprouts appear. Green onion seeds germinate best in a consistently warm environment, with an optimum soil temperature around 75°F (24°C). Temperatures between 68°F and 77°F (20°C to 25°C) assure a high germination percentage. Providing gentle bottom heat with a heat mat helps maintain this ideal temperature and accelerates sprouting.
Consistent moisture is equally important; the growing medium must remain damp like a wrung-out sponge, but never waterlogged. Covering the planting tray with a clear plastic dome or plastic wrap helps trap humidity and prevents the shallow soil from drying out quickly. Light is not required during this initial phase, so the covered trays can be kept in a warm, dark location. Under these conditions, the seeds typically begin to sprout within seven to fourteen days.
Early Seedling Care and Transplanting
The moment the tiny green loops of the seedlings emerge, remove the plastic covering to allow for air circulation and prevent fungal growth. These new sprouts require immediate access to bright light to grow strong and straight. Place the tray directly under a dedicated grow light set to run for 12 to 16 hours a day, keeping the light source within a few inches of the seedlings. This prevents them from stretching and becoming “leggy.”
Keep the soil consistently moist as the seedlings grow, ensuring it does not become soggy. When the young plants reach approximately six inches in height, they should be thinned to give the remaining seedlings adequate space. Instead of pulling out unwanted sprouts, use small scissors to snip them off at the soil line, preventing disturbance to neighboring root systems.
Before moving the seedlings permanently outdoors, they must be gradually acclimated to the harsher conditions of direct sun and wind in a process called “hardening off.” This involves moving the tray outdoors for increasing periods each day over one to two weeks before transplanting them into the garden or a larger container.