Grow Perfect Onions in Your Southern Arizona Garden

Bulb onions are listed in the top 10 most popular vegetables to buy in the grocery store. They're also pretty inexpensive. While onions are cheap to buy, growing your own offers superior flavor as well as a variety of options that you just can't find in the produce department. Just think about all the recipes you make that call for onions. Why not try growing this useful vegetable in your own garden this fall? Onions are also listed frequently as one of the vegetables gardeners struggle to grow. Either the bulb doesn't form or they go right to flower. I've struggled with onions in the past myself. Today I'm sharing my top tips for how to grow onions well in your home garden. When growing onions it's important to know that onions are biennials. That means they're a two-year plant. The first year the plant will develop the bulb. In the second year all of the energy that was stored in that bulb is tapped into and a flower develops to produce seed. And after that it starts all over again. Day length is what triggers an onion to begin forming the bulb. If you live in the north your days are longer than if you live in the south. When it's time to choose the onion variety you have three choices. Long day, short day, and day neutral or intermediate. Long day onions will start forming a bulb when the daytime hours reach 14 hours or more. Short day onions will begin forming a bulb when daylight hours reach 10 to 12. Day neutral onions need 10 to 12 hours per day to start forming an onion bulb. So you have long day at 14 plus, intermediate at 12 to 14, and short day onions at 10 to 12. When you're shopping for onion seeds or transplants choose the onion type that does best in your location. In southern Arizona short day onions are the best. Let's talk about your three options for starting onions. You can start from seed, from transplant, or from sets. Both have pros and cons. The benefit of starting from seed is that it offers you much more variety and it's a lot cheaper than buying transplants or sets. When you start from seeds you must have a good seed starting setup. Make sure that you have adequate light so that you don't end up with leggy plants. Starting from seed also takes more time. You're going to have to start your seeds inside eight to ten weeks before you plant them outside. The other option you have is buying transplants. You can buy transplants in a six cell tray from a local garden center or you can also buy small onion plants that come in a bundle. The benefit of these are that they offer a little more variety than buying onion sets but not as much variety as if you started from seed. They're also cheaper than onion sets but a little more expensive than seeds. They're pretty easy to transplant out. You simply prepare your soil ahead of time and then plant your transplants one inch deep. And if you start from transplant you don't need a seed starting setup inside with lights and things like that and it's obviously a lot quicker because growers have done the work for you. Transplants are started from seed by a grower. They're allowed to grow to a size and then when they have four to five leaves they're potted up in a seedling tray or bundled up in a small onion plant bundle that you can buy either online or from a local garden center. The upside of this is that it takes you less time because you're not starting and caring for seeds inside and you don't have to have a seed starting setup either. The downside is that you'll get a few less options than you would if you started from seed. They're also a little more expensive than seeds but less expensive than onion set. Which brings me to your third option which is starting your onions from onion sets. Onion sets were planted by a grower the season before allowed to get to a small bulb size and then they were dug up and stored until the next season when they're sold to gardeners across the country. The benefits are that it's really easy to just go put them into the ground when you buy them. You also don't need a seed starting setup for them. However you're going to have even fewer options than you would for onion transplants and of course from seed. The other downside is that many of the onion sets available to purchase are long day varieties and if you're in the southern regions of the United States those are not the best varieties for you. I want to talk for just a minute about why I don't recommend starting onions from sets. Growers who sell onion sets are taking advantage of the fact that onions are biennial or a two-year plant. The challenge with onion sets is that they know they're on year two and so naturally they want to flower and so if you have a cold snap or if there are dry conditions or the onion gets stressed out in any way that onion bulb is going to want to flower very soon. And of course if it flowers you're not going to get that nice bulb that you're expecting. If you live in southern Arizona August is the time to start thinking about sowing your seeds inside. You can sow seeds inside from August through November and if you want to sow your seeds directly outside shoot for October through November. And if you're going with planting transplants you can put those out in November through January so you've got quite a bit of time. Onions are a hungry plant and so it's important to prepare your soil before you plant either your seeds your transplants or your set. Before I plant my onion seeds or transplants I like to add a couple of inches of organic compost to my beds. If you choose to use a fertilizer either organic or synthetic you can also do that at the time of planting but there are certain fertilizers to add to onions at certain times so let's go through that really quickly. The first fertilizer you can add is phosphorus and phosphorus should be added at the time of planting. I like to use the trench method. First will dig a trench three inches deep then I'll add half a cup of high phosphorus fertilizer per 10 linear foot row. Then I will cover that line of phosphorus fertilizer with about two and a half inches of soil. This gives about a half an inch to the surface of the soil which is exactly what you need to sow your seeds in. So I'll sow the seeds and cover them with the last remaining half inch of soil. The process for transplanting seedlings and adding your high phosphorus fertilizer is similar. This time you're going to dig your trench four inches deep you're going to add your half cup of high phosphorus fertilizer per 10 linear foot of row and then you're going to cover with three inches of soil. This will give one inch of remaining space to the surface of the which is exactly what your transplants need. Add your transplants cover with the remaining one inch of soil and you're good to go. If you're looking for a natural source of high phosphorus fertilizer bone meal is available in organic options. Moving forward onions will need a high nitrogen fertilizer to produce good yields. You can side dress onions with a high nitrogen fertilizer for example 21-0-0 would be a good one which you want to add three to four weeks after planting and once a month thereafter until you get to about four weeks before harvest. You're going to side dress with one cup per 10 linear foot row of a high nitrogen fertilizer. If you're looking for an organic high nitrogen fertilizer option you can check out blood meal those are available in organic options if you choose to use it and of course when adding fertilizer always water it in well. As I said you want to stop using your nitrogen fertilizer about four weeks before harvest and you know that the time is getting near when you see the neck of the onion starting to soften you may see them starting to fold over but you want to check on that neck often to see if it's starting to soften and if it is cut off the nitrogen fertilizer. Remember what nitrogen does for the plant it encourages a robust growth of foliage which is not what we want as our onion is in its final few weeks of bulb formation. We want bulb growth not leaf growth. Onions do best growing in full sun so try to find a spot in your garden that receives at least six to eight hours of sun every day. If you plant your onions in a location where they get less sunlight than that you're going to end up with a lot of leafy tops but not a lot of bulb. I sow my onions in clumps so when I'm starting my seeds indoors and my seed cells I will plant four to five seeds per cell and then when I plant them outside I will plant them in that clump and I don't separate them out. As long as you have really rich fertile soil the onions should do just fine and make sure that you water them well enough because you've got four or five onions in one spot so they're going to require a little more water in each of those planting spots than they would if there was just a single onion growing there. If you're planting your onions in clumps I would give more spacing so I would say at least eight inches between each of those clumps. If you're planting single onions you can space them out four to six inches. I will say I've had better luck with six inch spacing the bulb seems to develop into a much bigger onion bulb which is exactly what you want. You want to space your rows eight to twelve inches apart and this spacing goes for sets seedlings or seeds. I think onions make one of the best companion plants. I plant them at the edges of my beds. I've put them in my flower pots which may seem a little strange but it actually adds some unique structure to the flower pot. Sneaking onions into little open spaces is a great way to increase productivity even if you're growing in a small space. Like all alliums onions have a shallow rooting system to about a depth of 12 inches. You want to ensure that your onions don't dry out so that you get good bulb formation. You can mulch so that in between waterings the moisture stays consistent. I like to water my onions to a depth of 12 inches so that I know that water is getting to the roots. Onions that are grown in dry conditions will have reduced yield, diminished bulb size, and not as good a flavor. If you're watering your onions too much they're going to tell you by their color. The color will be a pale green or even a yellow so hold back on the watering if you're seeing that color change. Can you prune onion tops? The answer is yes you can. When I was researching this topic I found a lot of disagreement but when I dug further into the science research shows that you can actually get greater bulb development if you prune your onion tops throughout the season. Now I'm sure you're not finding farmers running around trimming acres of onion tops with pairs of scissors. That would be an unsustainable thing to do. However for the home gardener it doesn't hurt to try trimming your onion tops to see if you can get a bigger bulb. The green onion tops are their leaves and the rings around the onion are actually the base of the leaves. If you have more leaves you have more rings and therefore a bigger bulb. One of the ways you know onions are nearing harvest time is when the tops start to bend and fold over and when this happens it crimps off the flow of energy from the tops which are photosynthesizing to the bulb and after that happens the bulb will stop growing. You can avoid this from happening prematurely by taking a clean pair of garden shears or scissors and trimming right above where the new onion leaves are emerging. Another thing that I like to do with the onion tops is to dehydrate them. I will either slice them up with scissors on my dehydrator tray so that they look like little chives and then after they're dry I will store them in a jar to use during the wintertime for nice fresh onion flavor or if I'm feeling lazy I will put the whole tops on the dehydrator tray and then after they're dry I will put them into my food processor and grind them up to make onion powder. Remember a well-groomed onion is a productive onion so don't be afraid to give those onion babies and onion adolescents a little haircut now and then. One way to know when the harvest time is near for your onions is by tracking the number of days. Most bulbing onions take between 100 and 120 days to mature. In southern Arizona this puts us at late April through early May. As the time gets closer you need to stop watering your onions. As I mentioned before you want to keep an eye on the onion tops to see when they're starting to get soft. They may even start to bend over. When you see either of these things starting to happen stop watering your onions and don't fertilize them anymore either. When the onion tops fall completely over they may or may not be turning yellow. At this point you know that the onions are ready to harvest. At this point you can leave the onions in the ground for a few more days and then it's time to pull them. If you have any onions that have bolted or gone to flower they're not going to store well so take those into your kitchen and use them right away. In most parts of the country it's recommended that when you pull your onions from the soil you lay them right next to where they came from and let those dry for a week or two until you take them to the location where you're going to be curing them. In southern Arizona by late April and early May it's already starting to get hot so I don't like to leave mine out in the direct sun because I feel that the bulbs can get sunburned and cooked. I will either take them and put them under a dappled tree and let them dry outdoors there for a week or two or I will just take them directly to the location where I'm going to be curing them. So whether you choose to lay them on the soil next to the bed you pulled them from, take them to a dappled location or take them right to the curing area just monitor them. This leads me to curing onions. If you want to store your onions for months they're going to need to be cured. You can do this by moving them to a location that's cool and dark but with good airflow. I like to use a wire shelf that I have. I'll either put it in a shady location on my porch or if it's too hot I will put it in a little unused corner of my house. You want to let them dry in this location for a couple of weeks. There are two things that will tell you whether your onions are done curing. First the roots should look dry and crispy and second the neck of the onion that space between the tops and the bulb should be nice and dry. If you cut into one of the necks and you see that it's still a little bit moist it's not ready yet let it cure for a little bit longer. When the onions are fully cured the skin is going to look papery and dry the roots are going to look crispy and that neck of the onion is going to be dry as well. Once your onions are cured you can trim some of the roots off and you can trim the tops of the onion off leaving about an inch of the neck intact. Now they're ready to store. If you're really fancy you can braid them into a braid much like people do with garlic but what I do is simply store them in a cardboard box or a basket in a cool place either in a closet or in my pantry if I have room for them and they should keep for months to come. Just check on your onions often to make sure they're not getting soft. If you see any that are sprouting tops or starting to get soft use those onions right away. I am going to include a few of my favorite varieties both red, yellow, and white in the description box below for you for the sake of time. If you would like to know which ones are my favorites refer to that. So those are the basics of growing great onions. If you're growing onions this year and you have a favorite variety please share it in the comments below. I'm Kara from Sow, Arizona. Thank you so much for watching. Until next time, happy gardening!