Onions, many other vegetables need time to germinate before spring planting
Spring gardens may seem distant in the midst of winter, but Kansas State University horticulture expert Cynthia Domenghini says it’s not too early to begin gathering seeds for the coming season.
In fact, many vegetables need to be started in January if gardeners intend to transplant them to the outdoor garden in March or April.
“Transplants for the vegetable garden typically require 4-6 weeks from seeding to transplant date,” Domenghini said.
Onions take longer, as much as 10-12 weeks. Domenghini said guidelines for vegetables commonly grown in Kansas are available in the Kansas Garden Guide, available from the K-State Research and Extension bookstore.
Look for the Average Expected Planting Calendar to determine when to start vegetable transplants.
For most vegetables, Domenghini offers the following tips for starting transplants indoors:
- Always use a disease-free, soilless planting media or seed-starting mix for seeds. The containers for seed-starting mix can be individual cups, trays or even recycled containers as long as they have drainage holes in the bottom.
- Fill the container with two inches of media and lightly cover the seeds with the mix after planting. Keep the soil moist until the seeds germinate, and keep the containers under lights in a warm location.
- When the seedlings have grown 2-4 small leaves, they are ready to be transplanted into small pots. This will allow them to continue growing until it’s time to transplant them into the garden.
“It’s important to give plants time to harden off before transplanting,” Domenghini said. “This should typically be started 10 days before the transplant date, and involves gradually acclimating the seedlings to the outdoor conditions by reducing the amount of water the plants receive, while slowly increasing their exposure to outdoor conditions.”
Starting onions indoors
Onions are typically planted in late March to avoid summer heat, so if growing them from seed, the plants need to be started 10-12 weeks before transplant date. That means as early as mid-January.
To start onions indoors, Domenghini suggests:
- Place seeds ½ to 1 inch apart in a tray filled with seed-starting media. Keep the tray in a warm location (75-80 degrees Fahrenheit) until seeds germinate.
- When the seedlings are 1-2 inches tall, move the tray to a cooler location (60-65 F).
- Provide adequate light and use a water-soluble, general-purpose fertilizer no more than once per week when seedlings reach 2-3 inches in height.
Domenghini and her colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens.
Interested persons can subscribe to the newsletter, as well as send their garden and yard-related questions to [email protected], or contact your local K-State Research and Extension office.
