How to grow the perfect onion in the AZ low Desert

I have had so many people ask me about how to grow onions successfully here in the Low Desert, that I thought I had better write a few destructions - oops sorry - instructions!

Anyway, here goes.........

You can start onions here either from seed or onion starts. Onions are a cool season crop and actually pretty easy to grow here. They like relatively good soil, but don't seem to mind clay soil too much ( unlike carrots, which hate clay soil). Avoid using soil sulfur as a soil amendment: this affects the onion flavor, making them incredibly pungent. Trust me on this one, as someone who inadvertently did this once, my poor watering eyes suffered terribly when cooking with them, never to be repeated ! I digress.....

You can start onions from seed in late September, either directly sowing the packet into the ground (making sure to keep the soil moist for good germination - not always that easy in September), or you could start the seed at home - no need for a greenhouse, it's warm enough outside. Plant the seeds in a large pot or I've even used a wallpaper tray with holes punched in the bottom. Whatever you use, make sure to keep it in the shade and evenly moist for good germination, following the packet instructions for sowing. One variety that I have had success is yellow granex, but there are lots to choose from.

The aim is to produce seedlings that are the size of small green onions for planting out in November. In other words, onions starts.

If you do grow them directly in the ground, you will need to thin them out and you can, in fact, then just transplant the thinned ones. I usually wait until a nice cool moist day in November to do this, (or so I hope, for such a day!)

If you decide to buy onion starts, you can either buy them online or pick them up at your local nursery. So here's the bit that is important. If the onions starts have dried out too much in transport, or before you buy them, this can trigger the plants to go to seed much more readily.

If you think about it, the primary function of the onion growing a bulb, is to make enough food storage, to then throw out a seed head (onions, believe it or not, are biennials), but as we have 2 growing seasons here in the valley, that can all happen in one year. IF the onions starts get too dried out before planting - that then triggers some internal mechanism in the plant to sort of go - aha, I need to make seed !! It then never really makes a proper bulb and will just grow a smallish bulb and throw up a seed head.

(Many of you have complained about this and wondered why - now you know).

So what's a gardener here to do ? Well.....make sure you buy as moist a bunch of onion starts as possible. Then, when you get them home, before planting, stick them in a bucket of water for about 24 hours or so. This should help immensely. Thus, by giving the "baby" onion plants a good drink of water and hopefully combatting the drying out, this should help to stop the "grown up" onions from going to seed. Clear as mud ??

Finally, plant the starts in your vegetable garden. Don’t plant them any deeper than old soil marks, which show how deep they were planted in the original growing field. Keep the starts moist until they look like they have taken and are actually growing new roots etc.

Happily growing onions

Onions are "heavy feeders" so provide adequate nutrients, in other words, they will probably benefit from a couple of supplemental feeds during their growing season. This will obviously help to form a larger bulb.

So what about that seed head ?

It is just part of the natural process of the onion life cycle. If the onion bulb was not harvested and left dormant in the ground, it would just sit there all summer, quietly biding it's time. Then, once cooler weather returned, the bulb would be triggered to use up the food stored in the bulb to throw up a seed head, in other words it would go to seed. Hence the biennial nature - 2 growing cycles.

The dreaded seed heads !!

We don't want that though, we want to have a nice fat onion bulb to harvest with no seed head.

But, you might ask - why is having a seed head so bad ???

Well, it does not allow good long term storage of the onion bulb at all !!

The seed head stalk is hollow, when it dries it leaves a hollow in the middle of the bulb, this causes it to go rotten much more quickly and thus is not good for storage. so obviously, this is not something we gardeners want - right ?

Okay, so now, having grown your onions successfully from September onwards, through the winter and spring, it will be time to harvest them. Round about early May, the tops will start to fall over - don't bend them, just let them do their thing naturally. If you bend them prematurely, this stops growth and thus you may get a smaller bulb.

When the tops start to turn yellow, then you can cut back on watering and let the bulbs ripen in the sunshine, but don’t leave them there much longer than a week. Pull them up and let them dry out further in a shady place. Do not dry them in the sun, our climate and hot sun will just scald and ruin them !

Drying onion

Once they are dry, remove loose soil and any really loose skin, but only the loose skin. You can store them in the legs of ladies panty hose, this allows good air circulation. You can even tie a knot in between each onion, thus making it easier to cut one off as you need it.

Nicely ripened onions will in fact store well into the new year. ( I store mine in my garage, hanging them up for good air circulation).

You should keep an eye on them, removing any that go mouldy. You will find that, round about December, they will start to sprout, even in the pantyhose, they are just trying to start the second part of their life cycle. Not a lot you can do about this, just use them up as much as possible.

So.... I can and do, in fact, start to use the onions in my garden from April onwards and then go right through to the following January, having no need to buy any onions at all. I must say, it absolutely kills me to buy onions January - March !!

Financially, a bunch of 50 onions starts usually costs around $3.50. I usually plant at least 3 bunches. This gives me more than enough onions to last me at least 9 months. so for $10.50, this is a great deal.

Please do contact me with further questions, I am happy to help, if I can.

( I have posted more onion photos on Instagram, just in case you are not totally bored by now!!)

Good luck and may you have much future success in onion growing.

Happy Gardening !!