If you want BIG onions, grow from seed! Dry bulbs, sold as ‘onion bulb sets’, were last year’s onions, and they really want to focus on flowering, so getting big bulbs from them is difficult. I chose January to write about onions because it’s time to plant them from seed! Yes! Any time between the second week in January to the second week in February!
Start indoors in a cool room. Basements or slightly heated garages are great for this. Plant seeds by sprinkling them over a tray of good moist potting soil. Lightly cover with vermiculite or fine sand, and cover with a short plastic dome. Use a grow light very close to your soil. Be sure to pay attention to the growth of your seedlings. You’ll want to raise the light and eventually remove the dome as the leaves grow.
Lights on for 16 and off for 8 is fine. The seedlings will start by looking like grass, and will eventually be pulled apart for planting. I like to ‘harden’ off my seedlings before planting them outside, by placing them outside during the day and inside at night. I start this the second week in March. Roots should start pushing away from each other by planting time in April. Plant them with plenty of room. If the bulbs touch, they will slow in growth and deform. Once planted, you can fertilize. Use a good organic mix 5-1-1 Alaska Fish fertilizer to really get those leaves big! Each leaf is attached to a ‘ring’ of the onion, so the bigger the leaf the fatter the ring, therefore the larger your onion!
Once leaves are thicker than your thumb (around July) then you can cut them all down by half. This method will help the onion focus on making that bulb even bigger. Scoop soil away from the bulb too, so that the bulb is sitting on top of the soil and only the roots are in the ground; this method is called ‘spooning the onion’ LOL. Once the leaves completely fall over at the neck, you can harvest them. Allowing them to dry (cure) for an additional 6 weeks in a cool dark location is recommended so that they will store for you all winter.
Sweet onions like Candy and Walla Walla are huge and sweet, but do not store long, so I only grow a couple of rows of these. Focus on growing onions with bold taste and excellent storing qualities. My favorite so far is Newburg from Snake River Seed Cooperative. The flavor is excellent. Having been picked in September, they are still beautiful in January!
Look for varieties known as Day-Neutral, or Long Day. These refer to onions that grow well in the north with longer hours of summer daylight. Short Day onions don’t do well here. They are for the south.