Grow your own onions from sets
How to grow onions from sets: well this is pretty easy, and these were the first crops I grew many years ago under the watchful eyes of my Dad. For the purposes of this page let's assume you are going to grow onions from sets rather than seeds.
Sets are really small onions whose growth has been stopped the previous season by the merchants and this is the easiest, and probably the best way of growing them unless you want to start growing from seed, transplanting etc. etc which is cheaper admittedly but do you really need the hassle?
Take a look through a reputable seed catalogue and they will have a variety of onion sets available. Not only that but they will have a description of what they will be like when fully grown and what the storage life should be after your crop is lifted.
I always buy sets as it saves time and they are screened by the seed company to weed out as many "bolters" as possible by heat treatment in the early stages of growth. If an onion bolts it will never form a proper bulb so as soon as you see a seed tip on one of yours you may as well pull the whole thing out and compost it.
Mark a line where you are going to plant and dib holes about 9-12" inches apart (slightly nearer if you have a raised bed). Simply push the sets into the holes you made but leave the onion tip showing above the surface. It's a good idea to cover the growing area with a net until your plants are well established, or about 3 inches high otherwise you'll find that Blackbirds pull them out thinking the green shoots are worms.
Just how you grow your onions depends on the size and shape of your plot and how windy it is in your area, but I grow mine in lines and because ours is a rather windy place I string? them by having stakes at each end of the line and strings in between them to keep the onions upright. I find that if the wind blows them flat they don't "bulb up" properly.
Keep your onions well fed and watered but not waterlogged and never feed or water them after the end of June as to do that affects them drying out properly later. If they aren't dried out properly they will rot before you have time to eat them.
When your onion leaves have all died off, and by that I mean gone brown and withered, you can lift them gently and leave them on the ground to dry off (internally) for a couple of weeks.
After that you can hang them by the withered stems somewhere out of direct sunlight for a further couple of weeks to finally dry out before storing them in a cool, dark and frost free area, ready to eat throughout the winter and following spring.
Our onions last us until the middle of April the following year.