We received many phone calls and emails with customers asking us about onion plant size. Onion Plant Size is determined by a few factors. Optimal plant size at the time of transplanting is about that of a pencil, ≈1 cm or slightly less than ½ inch in diameter, which usually translates to the plant having 4 leaves. If an onion plant has more than 5 leaves, it’s more prone to bolting, or going to seed, than a smaller plant.

Factors that determine the size of onions

When we ship onion plants, each plant has a certain amount of carbohydrates stored in the bulb. The larger the bulb on the plant, the more carbohydrates the plant contains. The drier the bulb, the more carbohydrates are stored since this solid fiber has not been diluted by water. As our loyal customers know, some onion plants in the bunch are smaller than others. Within a given bundle of plants, there may be a range of sizes of plants.  

Onion seed germination

Raw onion seed has around 80% germination. That means that 80% of the seeds will germinate within 14 days; some of the seed may germinate in as little as 5 days and the other seed may take 14 days.

This will mean that some of the plants are up to 9 days younger than other plants. Some growers may wish to take all the smaller plants and plant them in a separate area where they will harvest them as spring green onions.

bunch of green onions

Factors that impact the onion plant size within our inventory include:

Weather, variety, and popularity of a certain variety. This past fall, we received 18+ inches of rain in the month of September.

This greatly impacted our planting schedule leaving several weeks between plantings. In a normal season, we plant fields weekly from August through November. Growth rate between varieties vary greatly, as well. Red onion varieties and leeks grow a bit slower in the fields than white and yellow onion varieties; out of the same field planted on the same day, the red varieties may differ in size from the yellow and white varieties.


what makes onions sweet

If certain varieties are more popular in a particular season, we may harvest all of that variety out of one field, forcing us to move to a younger field, while other varieties are still being harvested out of a field that is one-to-two weeks older and more mature. All of these factors will impact the differing of size of onion plants.

Properly planting your onions

onion harvesting tips- onion field

Your job as an onion grower is to transplant the bulb, help it establish a strong root system, and allow it start generating more carbohydrates before it uses up all it has stored in the bulb; a simple explanation for a critical period in the life of your onion. It takes about two weeks for the onion to fully establish a root system. After that, it should start shooting out new leaves once every two weeks or so.  

The final size of the onion bulb is more effected by nutrition, climate conditions, and the variety planted than with the size of the transplant.   As always, we try to ship you plants that are as close to the optimum size as possible. Our guarantee promises that you receive healthy plants that will transplant successfully! 

To see our selection of onion plants available or place your orders, visit our  website . You may also contact Customer Service at (830) 876-2430 or email customerservice@dixondalefarms.com. We look forward to another of providing the highest quality onion plants for you.