How to Grow Onions

How to grow onions

Onions are a hardy plant making it very easy to grow them. When planting onions in the fall or spring, they will start being available for harvesting around mid to end summer. 

Types Of Onions

How to plant onions


No matter if grown in containers, a backyard garden or in raised garden beds, onions grow great in about 4 inches of soil. When planting onions, the spring and fall seasons are best for placing the onions in the ground. When planting onions outside, planting them in the colder seasons is more fit for the onions' growth. The best outdoor temperatures should not go below 28°F or -2°C. The fall-planted onion crop requires at least 4 to 6 weeks of warmer temperatures to grow and set its roots in the ground. They will remain inoperative during the colder part of the winter season but become primed and ready to grow when the spring comes around. Fall planted onions often grow more significant in size and are better in flavor than the same-year planted onions. 


When planning the garden space, prepare to plant the onions 4 to 6 inches apart from each other. And when growing onion in more than one row, plant each row 12 to 18 inches apart. Onions also require full sun with no shade from other plants.



Onion sets are just onion bulbs small in size and sold explicitly for gardening. An onion set will grow to full size in about 3.5 months. Onion sets are the best option when planting onions in the fall; they can handle frost damage the best.


When planting onion from seed, it is best to start them six weeks before planting in an outside garden. Germination temperatures need to be at least 50°F or 10°C.


The sprouts will grow from the center of the onion bulb. Remove the outer layers around the sprouted onion and separate and clusters. Place the sprouts root side down in a jar with 1-2 inches of water. After a few days, white roots will start to grow from the bottom of the onion sprout. Once there are white roots, the onion is ready for planting in the soil. Dig individual holes for each onion sprout, and cover it, so only the green piece sticks out of the ground.


Growing onions bulbs from scraps is a little harder than growing green onions from scraps, but it is still an easy task. Start by cutting the bottom of the onion off at around 1-inch thick piece of the onion. Place the onion bottoms cut side up and root down into damp soil. Next, cover the onion bottoms with a thin layer of soil. In around 2 to 3 weeks, green shoots will start growing. One onion base will likely grow multiple onion bulbs. Once the stems are a few inches in length, the bunch will need transplanting into an outside garden or containers with enough room for each bulb to grow.

How to care for onions


Growing Onions in a Container

Onions grown in containers will need at around 2 – 3 inches of water per week, sometimes even more during hot weather. Check your onions periodically, and if the top of the soil is dry, provide them with some water.


Growing Onions in a Garden

Commonly, onion plants do not need constant watering when covered with mulch. About 1 inch of water each week (including rainwater) is adequate. Water more often for a sweeter onion. Plant onions in the spring season when growing outside in frigid regions.



Thrips are tiny, have tan-colored bodies, and are very fast in movement. Insect sprays and blue or yellow sticky traps help remove them from the onion.

Onion Maggot

Onion maggots thrive on decaying organic matter and are more of a problem during the rainy seasons. Removing the entire plant when harvesting will help prevent the onion maggots. If onion maggots appear, cover the soil with a mesh netting to prevent them from laying eggs.

How to harvest onions


Any onions that grow a flower stalk have stopped growing and should need harvesting right away. Onions with a flower stock won't store for long and is best when used within a few days of harvesting. 

A mature onions tops will yellow and start to fall over. Once this happens, bend the stems down or even step on them, promoting the ripening process. It is good to loosen the soil around the bulb to help encourage the bulb to dry out. When the top becomes brown, pull them out of the ground. 



Cut the tops to be 1 inch from the bulb and cut the roots off. The onions will need to cure in a dry area and ground for a couple of days; for more extended storage, onions will need several weeks spread out on an open screen off the ground and giving time to dry before storing in dark areas. 

Fun fact, onions have been around since the Bronze Age; the oldest know onion harvest is around 5,000 BC. 

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