Onions can be set out early in spring, which makes them a good plant to be seeded for transplanting in January.
Prepare for the spring by starting onion plants indoors
K-State's Upham shares tips on starting onions from seeds
Dec. 22, 2022
By Maddy Rohr, K-State Research and Extension news service
MANHATTAN, Kan. — Starting the new year with indoor gardening is a great way to prepare for spring, said Kansas State University horticulture expert Ward Upham, who encourages onions to be started in January.
“Onions are one of the first plants to be seeded for transplanting because this crop takes a significant amount of time (6-8 weeks) to reach transplant size and because they can be set out relatively early (late March in much of eastern and central Kansas),” Upham said.
Upham said onion seeds should be placed 1/2 to 3/4 inch apart in a pot or a flat filled with seed starting mix.
“Place the container in a warm (75-80 F) location until young seedlings emerge,” Upham said. “Move to a cooler location (60-65 F) when the seedlings are 1-2 inches tall.”
Upham recommends plenty of natural or fluorescent light as well. Begin fertilizing when the plants become 2-3 inches tall.
“Onion seedlings tend to be spindly with the remains of the seed sticking to the end of a leaf for several weeks. Encourage stockiness by trimming the ends of the leaves when the plants reach 4-5 inches tall,” Upham said.
Onions can be moved to a protected outdoor area beginning in March.
“You may have to move them inside temporarily to protect them from extreme cold snaps,” Upham said.
Upham and his colleagues in K-State's Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens. The newsletter is available to view online or can be delivered by email each week.
Interested persons can also send their garden and yard-related questions to Upham at wupham@ksu.edu, or contact your local K-State Research and Extension office.
