Growing Onion Seed: Planting Onion Seeds In The Garden

Rows Of Planted Onion Seeds In Soil
(Image credit: Jurgute)

Growing onions from seed is both easy and economical. They can be started indoors in flats and transplanted to the garden later or sow their seeds directly in the garden. If you know how to grow onions from seeds, either method for planting onion seeds will yield an abundant supply of onion crops. Read on to learn more about onion seed starting.

How to Grow Onions from Seeds

Onion seed starting is easy. Onions grow best in fertile, well-draining soil. This should also be worked with organic matter, such as compost. Onion seeds can be planted directly in the garden bed. However, when growing onion seed, some people prefer to start them indoors. 

This can be done in late autumn. The best time for planting onion seeds outdoors is in spring, as soon as the soil can be worked in your area. Place them about an inch (2.5 cm.) deep in the soil and approximately half an inch (1 cm.) or more apart. If planting rows, space them at least one and half to two feet (46-61 cm.) apart.

Onion Seed Germination

When it comes to onion seed germination, temperature plays an active role. While typically germination occurs within seven to ten days, soil temperature affects this process. For instance, the cooler the soil temperature, the longer it will take for onion seeds to germinate -- up to two weeks. Warm soil temperatures, on the other hand, can trigger onion seed germination in as little as four days.

Growing Onion Seed Plants

Once seedlings have sufficient leaf growth, thin them down to around 3 to4 inches (8-10 cm.) apart. Transplant onion seedlings that were started indoors about four to six weeks before the last expected frost or freeze date, provided the ground is not frozen

Onion plants have shallow roots and require frequent irrigation throughout the growing season. However, once the tops begin to lay over, usually by late summer, watering should be stopped. At this point, onions can be lifted. Growing onion seed plants is an easy, inexpensive way to keep an unlimited amount of onions on hand just when you need them.

Nikki Tilley
Senior Editor

Nikki Tilley has been gardening for nearly three decades. The former Senior Editor and Archivist of Gardening Know How, Nikki has also authored six gardening books.