How to grow Onion

Keep onion sets free from weeds as grass and weeds tend to compete for nutrients and moisture. Side apply fertiliser during the season if need be.

Try and keep the moisture levels in the soil as consistent as possible – applying mulch is often a good idea. This reduces bolting

Growing onions from seed can be trickier than growing from established sets, but it is possible, and can often produce more disease resistant plants.

Sow into flats in a soilless medium and keep in a warm place for about a week to germinate.

Sow at a depth of approx. 0.98 inches (2.5 cm) and aim for a distance of at least 1.95 inches (5.0 cm) between Onion plants. Soil temperature should be kept higher than 13°C / 55°F to ensure good germination.

By our calculations*, you should look at sowing Onion about 28 days before your last frost date .

Onions are often transplanted from sets – this is typically the quickest and most foolproof strategy to grow onions as growing from seed can be problematic. Sets (or bundles) can be purchased from garden stores and over the internet, and typically contain around 60 – 80 plants.

Onions can be planted out as soon as the ground can be worked in the spring. If you are growing to harvest as green onions, seedlings can be planted quite close together as they will be harvested before they reach full size. If growing for mature dry onions, try to plant as far apart as practicable and thin and use as green onions as you go if you misjudge the distances initially. Keeping good distances between plants is very important for achieving good onion bulb size.

Ensure that temperatures are mild and all chance of frost has passed before planting out, as Onion is a hardy plant.

Harvest onions when the tops turn yellow and begin to topple over. To dig them up, loosen the soil around each bulb and then lift them up carefully – make sure not to damage as they can rot quickly.

Spread them on a flat surface above the ground and leave to dry out – this will take anywhere from 2 to 10 days if left out side, or 2 weeks if taken inside. Cut the tops, and then store in mesh bags in a cool, well ventilated space. Alternatively the dry leaves can be platted and the bulbs made into a decorative onion string for storage

Onion seeds can be saved by carefully cutting off the flower head (floret) when the seeds have fully developed, and then placing in a paper bag in a cool dry location for a couple of weeks.

These estimates for how long Onion takes to sprout, grow and harvest are from real observations from real gardeners, right around the world.

Our when to plant Onion estimates are relative to your last frost date.

The common name of “Onion” is probably derived from the Latin unus, meaning “one.”

• Onion is said to relieve the pain of dog bites and toothaches.
• The Romans are said to have brought the Onion to England.
• Growing onions in warmer climates tends to produce sweeter tasting onions.

The flavonoids are concentrated on the outer layers of the onions, so peel as little as possible of the edible portion when removing the outermost paper layer.

Eating several servings of onions each week may be sufficient to lower your risk of some types of cancers. For colorectal, laryngeal, and ovarian cancers between 1-7 servings of onions has been shown to provide risk reduction. For decreasing your risk of oral and esophageal cancer, you’ll need to consume one onion serving per day (approximately 1/2 cup).²

Herodotus (~485-425 BC) wrote that the builders of the ancient Egyptian pyramids were paid in radishes, onions and garlic³.

Garden onion, Common onion, Cebolla

Allium cepa Cepa Group, Allium cepa (Cepa Group)

Misspellings: Oignon, ognion, Allium capa, Onions

¹ Cass County Extension

² Onion-The world’s healthiest foods

³ :The Encyclopedia of Medicinal Plants: A Practical Reference Guide to over 550 Key Herbs and Their Medicinal Uses; Andrew Chevallier; published 1996