Plant onion seeds every 1″ along a row. When the plants reach 4″-6″ tall thin them down to every 3″-4″ apart and you can eat the thinned plants as green onions. Plant onion sets/bulbs and transplants every 3″-4″ apart along a row.
If you want to grow onions for green onions instead of baseball size onion bulbs you can keep the onion plant spacing at 1″-2″ apart.
Or you can do a combination of both by planting onion seeds or sets 1-2″ apart and then thinning down to 3″-4″ apart when the plants reach around 6″ tall.
If you’re goal is to produce large onions give the plants more space by spacing onion plants 5″-6″ apart.
|Source||How Far Apart To Plant Onions||How Far Apart To Plant Onion Rows|
|University of Minnesota Extension||3"-4"||12"-18"|
|Connecticut Garden Journal||6" apart in all directions in a bed|
|University of Maryland Extension||2" apart for green onions, 4" apart for moderate size bulbs, 8" apart for large bulbs||12"-24"|
|Study #1||4.5 plants/square foot|
|Study #2||5.5" apart||6" between rows|
|Texas A&M Agrilife Extension||Plant seeds 1" apart and thin down to every 2"-3" apart. Plant sets/bulbs/transplants 3" apart.|
|Utah University Extension||3"-4"||In Beds 26"-44" center to center|
|University of Illinois||6" apart in all directions in a bed... 4" apart in rows||12"-18"|
|University of Arkansas Division of Agriculture||Plant 12-15 seeds per foot and then thin down to plants 4"-5" apart||12"-15"|
|Ohio State University Extension||Planted 2"-3" apart and thinned to 3"-4" apart|
|Iowa State University Extension||2"-3" apart||12"-15"|
|Mississipi State University Extension||4"-6" apart|
|Purdue University Department of Horticulture||1" apart for green onions... 3"-4" apart for onion bulbs|
Onion Spacing Vs. Yields
Most garden plants have a similar result in spacing vs. yield studies. The higher the plant density the better the overall yield. However, the size of the produce and amount of produce per plant will decrease.
Onions only grow one onion per plant so that’s not relevant, but the size of the onions is. The tighter the plant density, the smaller the average onion becomes. Some markets pay a premium for jumbo size onions so farmers have to take that into consideration.
Desired bulb sizes and marketable classes vary by region, but generally marketable onions are those that fall in the medium to super colossal size classes, with the larger bulbs being the most valuable.Seminis – Onion Planting Density
This study is titled Onion Variety Response To Plant Population and Irrigation System. The study was conducted by Oregon State University in 2012.
Four varieties of onion were grown with 5 different plant densities: 90,000 plants/acre, 120,000 plants/acre, 160,000 plants/acre, 200,000 plants/acre.
200,000 plants/acre = 4.5 onion plants/square foot
There were three different irrigation systems used in the study: conventional drip irrigation, intense bed drip irrigation, and furrow irrigation.
All four varieties of onion that were grown had an increasing yield sequentially from the lowest to highest plant density.
The above information is taken from table 6 of the linked study, which is the average onion yield for the four different varieties grown with the three irrigation systems.
In this study onion plant spacing vs. yields were evaluated by the University of Georgia Extension. Two varieties of onions were grown both with 4 different spacings used.
- Standard: 12 inch between row and 5.5 in. in-row (66 sq. in.)
- HD1 High density: 6 inch between row and 5.5 in. in-row (33 sq. in.)
- LD1 Low density 1: 12 in. between row and 11 in. in-row (132 sq. in.)
- LD2 Low density 2: 24 in. between row and 5.5 in. in-row (132 sq. in.)
HD1 roughly equals 4 onion plants/square foot
Standard roughly equals 2 onion plants/square foot
In both cases the onions yields were highest with the highest plant density (HD1) and second highest with the second highest plant density (Standard).
How Much Space Does an Onion Plant Need?
To grow onions for onion bulbs the closest you want to plant onion plants is 9 per square/foot or one plant per 18 square inches. To grow green onions you can grow 20 per square/foot.
Or, you can grow both by planting tightly, 20 onions per square/foot, and then thinning down to 9 plants when they reach 6″ high and using the thinned plants to cook with as green onions.
How Far Apart To Plant Onions in Raised Beds
An easy way to plant onions in raised beds is to space them 6″ apart in every direction. Another option is to plant them 3″-4″ apart in rows that are spaced 12″ apart.
How Many Onions To Plant Per Container
Onion plants need at the least 1 gallon of dirt per plant. The onion plants should be spaced 4-6″ apart to grow onion bulbs, if you want green onions they can be closer, 1″-2″ apart.
Use a container that is at least 9″ deep and make sure to create drainage holes if you use something lying around the house as a container.
Plant onions in shapes to create equal spacing. A triangle, diamond, pentagon, hexagon, etc.
What Happens If You Plant Onions Too Close Together?
If you plant onions too close together you’ll get small underdeveloped bulbs. The onion plant won’t have enough space to develop a good sized bulb and may not have enough nutrients, water, and sunlight to develop a good bulb with other plants too close to it.
How Deep To Plant Onions
Plant onion seeds 1/4″-1/2″ deep, onion sets/bulbs 1/2″-1″ deep, and onion transplants about 1″-2″ deep.
Please comment below with your own thoughts on how far apart to plant onions or anything else related!