Fat Onions
By Andrea Peck
Does anyone out there know how to grow big, fat onions?
So, what's the secret? I go to the local hardware store or nursery and I buy the little red onion sets and boom, year after year I get green onion tops and plum-sized onions. This year I did it all – I dug up that soil so that it was loose and looser. The soil is nice, well-composted, rich and loamy. They have their own designated spot, which the dog was using as a latrine for a while, but is now completely blocked off by free-pile finds and a window screen. Their plot is the most revered section of my garden. And they end up little more than green onions. What gives?
I decided to do some onion sleuthing. It turns out that the type of onion you choose, and the time of planting are crucial. San Luis County does best with “short-day” onions. “Intermediate day” onions are also a possibility. Apparently, where you live, and more specifically, the length of your day, affects the growth of the onion. The time of planting is an important element also. Onions should be planted 6 weeks before the estimated last spring frost. Your plant is affected by the weather, day length and season. Go figure.
It looks like I missed my window this year! But, that is okay – I am going to make a note in my calendar for December. Maybe I can ask for onion starts for Christmas. In the meantime, I can do a lot to prepare.
Onions thrive in a sunny location. Raised beds or raised rows are the very best way to plant onions. They require good drainage and prefer soil that hovers in the 6.2 – 6.8 pH range. If the soil is too acidic, you can add limestone. If it is overly alkaline, peat moss will balance it out. (Note to self: check soil pH.)
One method of planting involves a “fertilizer trench.” Basically you dig a center trench that is 4” wide and 4” deep. In this trench, sprinkle a half cup (per ten feet of row) of 10-20-10 fertilizer and cover that with 2” of soil. Do not plant in the trench. Instead, plant onions 6” away from the trench on both sides. Plant onions 1” deep. Don't make the mistake of planting onions too deeply, this inhibits growth. Leave a 2” space on the other side of the onion to allow enough built-up soil for the onion to grow and space onion plants 4” apart. If you are like me and like lots of onions, maybe another row is a good idea. Just be sure to place your next trench row far enough away. About 36” from the center of one trench to the next is recommended.
Now, for a sort of sore subject: watering. Onions love warm sun, but they also require adequate watering. They are not drought tolerant. So keep them moist the best way you can. Take less showers – whatever you have to do to pamper your plants. They deserve the sacrifice if you ask me.
For optimal growth, fertilizing is essential. Again, make sure your soil is at its best to begin with, but every two to three weeks feed your onions in the trench area. Ammonium sulfate 21-0-0 is recommended in alkaline soils. Calcium nitrate 15.5-0-0 is recommended in acid soils. Use ½ cup per ten feet of row and sprinkle this in the trench like before. Always water after fertilizing. When the onion grows large enough to start splitting the soil around it, fertilizer is no longer needed. Use a light covering of straw or similar mulch to keep weeds at bay and moisture in. Onions should have at least 13 leaves before harvesting. Brown, yellow and falling over leaves are an indicator that harvest is imminent.
So, those are some expert ideas that I am lucky to have gleaned. I am sure this is not the only way to grow large, spherical onions, but I guess I have plenty of time before planting to search for more methods and ideas. If you are an expert onion grower, I'd love to hear your tips, ideas and comments!