How to Grow Onions
In this article, we share a comprehensive guide to growing onions at home.
Quick Guide Information
Common Name: Onions
Scientific Name: Allium cepa
Family: Amaryllidaceae
Life Span: Annual
Time Till Harvest: 100 - 120 days
Light Requirement: Full Sun to Partial Shade
Optimum pH: 6.0 - 7.0
Onions are a staple ingredient to any dish and an essential for a savory garden to table meal. They can be easily grown as a cool weather crop and the bulbs can be stored for months, so there is never over planting! They are closely related to garlic, leek, and chives, and their management is somewhat similar.
There are various types of onions to choose from, all of which grow in similar conditions. This means fertile and moist soils, and relatively cool temperatures. One thing to consider is that different types of onions do best at different latitudes because of day-length.
Near the poles where day length can exceed 15 hours in the summer, gardeners can grow any type of onion. As you approach the equator and day length shortens, gardeners should consider growing intermediate or short day-length varieties. Usually seeds or starts you find at a local nursery will be adapted to your region, but consider this if you are ordering seeds online.
Propagation, Planting, and Maintenance
It is generally considered best to start onions by seed directly. This promotes bigger and more robust bulbs as opposed to plants that are transplanted. Thus being said, many people have wonderful results transplanting as well but it can be a bit more sensitive.
To plant onion, you want to sprinkle seeds in rows along your bed or planting area. To this by making a shallow “trench” with your finger about 1 cm deep and sprinkle with seed. You will eventually want plants to be 3-5 cm apart, but it is best to over plant and thin later.
After about 3 weeks you can thin plants so they are 3-5 cm apart. You can attempt to transplant any plants that you are removing. When transplanting it is important to not bury the bulbs too deeply. Add mulch to help reduce weeds and to hold moisture.
Make sure to weed beds regularly and prevent the growth of large obnoxious weeds. Onions can be very difficult to weed around and young plants are easily disturbed by weeds. If needed, cut weeds at the base instead of pulling them out by their roots.
Onions can really be harvested as soon as you want to remove them. Young onions can be harvested as tender green onions while if left to mature they’ll grow big and will do better for storage. To store onions, first hang them by their leaves and allow to dry for 2-3 weeks before storing in a cool place.
For seed, you will have to let your onions grow for another year. They require 2 seasons before flowering and going to seed.
Common Problems
No Bulb Formation - Soils too rich in nitrogen can cause lots of vegetative growth with little bulb formation. This can also happen when plants are too close together.
Bulb Rot - This can happen when planted in beds with unfinished compost and actively decaying material such as fresh manure. Waterlogged soils can also cause this.