|Onions growing in the garden with Tricolor Salvia – Makes for a pleasing planting|
It is now the end of the year, literally it is Dec. 31, and I have to admit my mind is more on staying warm during this frigid cold weather here in the Colorado foothills than gardening. However, I do like to grow onions from seed and it is time to start planning. Onions require about 14 – 16 weeks from the time of starting from seed to planting the starts outdoors. In order to be ready for a May planting here in my Zone 5a garden at about 8000’ that means getting those seeds started indoors in January.
There are three choices for starting onions – from seeds, transplants or sets. I like the greater variety available by starting from seed. An added benefit is that you can harvest those baby plant trimmings and eat them when you have nothing else growing. When buying onion seed, only get the amount you will use during the current growing season. Onion seed viability starts to decrease significantly after one year. If you want to check any older seed you have, it is easy to do a germination test by placing some of the seed on a wet paper towel and placing it in a plastic bag or air tight container in a warm place. The viable seed should start to sprout in about a week or less at 70°F. Some houses may be on the cool side in January so look for a warmer spot like the top of a refrigerator or under a light.
|Used salad containers make great onion starting containers, nice depth|
The plastic containers used for salad mixes makes a great seed starting container. Onions need depth for root development. The young plants also need adequate lighting. 12 hours underneath florescent lights per day is sufficient. Keep the lights within inches of the growing seedlings. As the seedlings grow, trim them to keep at about 3 inches in height. When the plants have started to send roots to the bottom of the container they can be transplanted to new individual containers (plastic cups with drainage holes are a good option). Groups of three seedlings per cup are fine.
Plenty of light, regular trimming and light feedings of nutrients should give you great plants for transplanting into the garden. I have found Copra to be a great onion for my area. It is a nice size, flavor and great storage onion.
Some great references: