One onion grows per onion plant. There is one variety of onion known as the potato onion, or multiplier onion, that grows around 5 onions per plant. The potato onion is classified scientifically as Allium cepa var. aggregatum, and is more closely related to the shallot or garlic than most onions.
The potato onion gets its name because it grows similar to the potato. You can plant one potato onion and it will grow into multiple onions, also how it gets its other name, multiplier onion!
Potato onions are an heirloom strain that used to be more commonly grown. They produce medium sized onions in a cluster.
Not to be confused with the gardening method of planting regular onions in clusters, normally 4 onion plants right next to each other. Planting normal onion plants in clusters is a gardening technique to make weeding between plants easier.
You might hear the term bunching onion. Bunching onions refers to varieties of scallions or “green onions” that do not form an onion bulb.
As far as I know all types of onions grow green growth above the ground that we can eat as green onions but some varieties of onions are known for being better producers of that top growth we call “green onions”.
How Many Onions Grow From One Seed?
One onion seed will produce one onion plant. A single onion plant will have up to 13 leaves that grow above the ground but they will all be coming from a single bulb.
However, you can grow multiple onions from a single sprouted onion. After an onion is harvested and stored for some time it might begin to sprout. A sprouted onion can be divided and replanted as multiple onion plants that will regrow into onions.
How Many Onions Should I Plant?
If you use 5 onions a week you should grow around 120 onion plants. That will supply you with onions for 6 months.
Onions can be planted as densely as 9 onions per square foot so to grow 120 onion plants at that plant density you’d need about 15 square feet. Planted at this high density onion bulbs will only grow into medium sized onions.
Check out “How Far Apart To Plant Onions” to learn how plant spacing affects onions.
How long onions can store is another factor to consider. If you’re a gardener in the north you’ll be growing long day onions that can store for 6 months+.
Gardeners in the south grow short day onions that will store for about 3 months. Check out “Long Day Onions vs. Short Day Onions” for more on that.
How Many Onions Are Harvested Per Acre
In this grow trial by Oregon State University four different varieties of onions were grown with different plant spacings and three different watering systems used.
They yields of the onion are measured in cwt per acre. Cwt is a measurement called a hundredweight and 1 cwt = 100 lbs. I converted it to lbs. for simplicities sake.
This is the averages for the four different onion varieties grown: Vaquero – 112,440 lbs. per acre, Barbaro – 109,490 lbs. per acre, Sedona 95,570 lbs. per acre, and Esteem – 97,040 lbs. per acre.
As Seminis points out, total yield by weight is not the only concern farmers have. Size of the onions produced is also important because the market pays more for larger onions.
Generally as onions are planted tighter together the overall yield by weight will increase but the size of the onions produced will decrease.
Farmers need to do their math and find a medium ground or choose a specific target market for the onions they grow.
What’s It Cost To Grow an Acre of Onions?
Here’s a cost analysis done by UC Davis in 2006 on the expected cost of farming an acre of onions in the San Joaquin Valley of California.
Operation – Land prep, irrigation hose and setup, fertilizer, pesticides = $1,862
Harvest – Grade and pack, load and haul = $1,846
Cash Overhead – Land rent, insurance, repairs, interest on startup capital loan – $369
Total Cash Cost Per Acre – $4,167
Onions are sorted into 40 lb. boxes. At $7.00 a 40 lb. box a farmer that yielded 350 boxes per acre would lose $983 per acre. A farmer that yielded 650 boxes per acre would earn $224 per acre, and a farmer that yielded 950 boxes per acre would make $1,435 per acre.
If a 40 lb. box of onions went for $10.00 instead of $7.00 that same farmer that made a $1,435 profit per acre would now make $4,285 per acre.
How Many Bulbs Does an Onion Plant Produce?
An onion plant produces one bulb and up to 13 leaves of top growth that can be consumed as green onions. The exception is the type of onion called the potato onion or multiplier onion that will produce 5 or so bulbs per plant.
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