Introduction: Starting Onions From Seed
Growing onions from seeds has a few advantages and some disadvantages as compared to planting sets or buying the plants.
-you can grow the variety you want instead of what retailers may have
-your plants will already have roots started while sets have to start growing them
-purchased plants, in my opinion, are ridiculously expensive
-fewer plants will bolt (flower)
-you may need to get your seed via catalog or by going to a garden center
-you have to start seeds 10-12 weeks ahead of planting
-you need to have the space and lots of light
-like any seeds started indoors, you need to tend them daily
1) seed starting soil mix
2) plastic containers with drain holes
3) growing area with lots of light
4) a plastic tray, with transparent lid, for the containers
Step 1: Getting Started Indoors
In southern Wisconsin I start onions in late January or early February in my basement.
Fill your plastic pots, I use 4" x 4", almost to the top with seed starting soil mix. Thinly scatter the seeds over the top of the soil so the seeds are 1/4" -1/2" apart. Cover the seeds with another 1/4" of soil. Repeat until you have all of your seeds planted. Place all of the pots in the tray on a level surface and put about 1/2" of water into the tray. The water will be drawn into the pots to water the seeds. Add more water if needed. Bottom watering insures that seeds and soil are not disturbed. After a few hours, temporarily remove the pots from the tray and dump out the remaining water.
Replace the pots and place them in a very well lit, warm area. I start mine under fluorescent lights and place a transparent cover on the tray until the seeds sprout. Once the seedlings start to emerge any cover must be removed to allow air circulation or a fungus called damping off disease may grow at the soil line and kill your seedlings. The seeds may take a week or two to germinate. Check them daily to make sure the soil is moist but not wet. A cover over the pots will help hold in the moisture. Keep the pots as close as you can to the fluorescent tubes, if you are using them, for maximum light. A transparent cover will also help to warm the soil to speed germination. Think about a closed car on a sunny day.
As the plants grow they look much like grass with round, not flat, stems. It is recommended that when the seedlings are 5” tall, use scissors to trim them back to 2”. This will encourage them to grow thicker and stronger.
About two weeks before planting, you need to begin hardening off your plants by moving them outside each day. Start out by placing them in a semi-shaded area for a few hours and slowly increase the amount of sun the plants get and how long they are out. Going directly from indoors under lights to outside in full sun will sunburn the tender plants.
Step 2: Putting the Plants in the Garden
When you have the garden ready to plant, you will need a bucket of water, a watering can, and a hoe. Use the hoe to dig a shallow trench for the plants. Gently grasp the tops of the plants, invert the pot, and tap the edge on the pot on the bucket to remove the soil and plants from the pot. Still holding the onion tops, insert the soil into the water and gently shake it until the soil has all fallen away from the roots.
Remove the plants, one by one, from the clump and place the roots in the trench. Position plants 5-6" apart, more if you have a variety that will grow very large. With several feet of row planted, water the roots to moisten them and to help settle the soil around the roots. Fill in the trench and water again to settle the soil. Continue planting.
For the next couple of weeks make sure the plants get sufficient moisture. Throughout the growing season keep your onions free of weeds and grass. When the tops die back in the Fall, harvest and cure your crop in a single layer in a warm, airy place before storing.