It’s time to plant onions for a good spring crop

By Grant Guggisberg

Nothing is more anticipated for a gardener than planting the first seeds of the season. I like the challenge of growing onions from seed.

You can purchase onion plants and plant them in late March.

My sweet Spanish yellow onion seeds are in the process of sprouting. 

Onion plants from seed can take from 6 to 10 weeks growing indoors. For my situation, the 10 weeks is common. I also use my onion plants to show to youth in our 4-H school garden programs. My onion plants need to be ready by mid-March.

Many plants from seed sprout well at 75 degrees. The optimum range for onion seed is 50 to 95 degrees. Seeds should sprout in four to 10 days. Once all the seeds have sprouted, these cool season plants need to be grown between 55 and 75 degrees.

The temperature can be controlled indoors as well as the light.

I use two 40-watt florescent lights. They are left on continuously. The onion leaves are just touching them.

My onions are started in a plastic tray. I place moistened new seeding mix in the tray and the seeds are covered with š inch of the seeding mix. The seeding mix is kept constantly moist. As the plants grow, a little bit of fertilizer is added to the water.

One of the fun things about growing onions from seed is giving them a trim.

When the leaves start to drupe, you can trim them back to 3 inches. Use the trimmings in your food preparation.

Bulb mature size is dependent upon the number and size of the green leaves or tops at the time of maturity.

For each leaf there will be a ring of onion. The larger the leaf, the larger the ring will be. The onion will first form a top and then, depending on the onion variety and length of daylight, start to form the bulb.

Onions are characterized by day length. “Long-day” onion varieties will quit forming tops and begin to form bulbs when the day length reaches 14 to 16 hours.

To be successful, keep your onions growing rapidly. They will need frequent nitrogen fertilizer and moisture, not too much, but evenly. Keep all weeds removed.

If the spring is cool and I have time to follow the directions, it will be a bumper crop of onions this summer.

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