I’ve been growing my onions from seed for many years now and have learned a lot in the process. They’re not really the easiest thing to grow from seed, nor are they the hardest. There is quite a bit of management that goes into starting onions from seed, but it’s a process I will always go through for one simple reason.
Onions seeds need to be started very early in the season.
So when the rest of your garden is still a dream, the reality of getting your fingers in some soil and cultivating a bit of plant life when the world is frozen, covered with ice and snow, is made possible by sowing onions in the dead of winter. They fan the flame of spring hope early for me and extend the growing season beyond it’s normal bounds.
Starting onions from seed has other advantages as well. It gives you the largest selection of cultivars to choose from. There is a much wider variety of seeds out there than sets. Onions started from seed often grow more successfully than those grown from sets. However, onions require a long season, often more than 100 days and that is one advantage to sets.
Last year, I hatched a plan which I still think is brilliant though it was unsuccessful for reasons beyond my control, whereby I started onion seeds from such a variety of cultivars where I could start them all at the same time and but their days to maturity were staggered in such a way that I would have a continuous harvest throughout the season with very little worry of storage until the late fall harvest.
Purplette- 60 days (2 weeks)
Red Marble- 75 days
Gold Coin or Bianca di Maggio- 80 days
Bridger- 90 days
New York Early or Ailsa Craig- 100 days
Cabernet- 105 days
Sierra Blanca- 109 days
Red Wing- 118 days (plant enough for storage)
Since space is at a premium in my basement (where I start my seeds) and I don’t want any wasted space I will “chit” or pre-sprout my onion seeds.
In a nutshell, “chitting” is starting your seeds in a wet, soilless environment. A couple reasons you may be interested in doing so would be to give the seed a jumpstart or to accurately ascertain your germination rate.
The first year I chitted my onion seed, I did so by sprinkling the seeds over one wet paper towel, covering them with a second wet paper towel, and then wrapping them with plastic wrap. I set them on the plant stand under the florescent light and misted them with a spray bottle filled with water when the towels began to dry out.
I waited way, way too long to transplant the seedlings. (Otherwise the spray bottle step wouldn’t have been necessary. But it’s good to know, if your seeds are slow to start or if you wrung out your towel too well, you may need it.)
The little shoots had begun to grow long and worked their way in between the fibers of the paper towel and many were lost when I tried to pull them out. Then I tortured the poor babies by planting them in the soil mix upside down! When the root that was sticking up in the air began to dry out and shrivel, I realized my mistake and corrected it. But before you laugh at me, please realize that I was picturing the seed down in the soil and then the shoot comes up out of it, so I planted the seed down. Onion seed shells grow up with the seedling and sit on top like a little black cap.
I lost many seedlings between those two mistakes. What I didn’t lose in seed starting was lost later in the garden when I poorly chose the location for planting and then lost the weed battle. Onions hate weeds.
My yield- zero.
Trial and error has taught me much since then and when I start my onion seeds later this month, this is how I’ll be growing them. Do yourself a favor and learn from my mistakes and experience.
How to Grow Onions from Seed
• Chit seeds by sprinkling them over moist paper towels and wrapping in plastic to retain moisture. Normally I sprout our seeds in a germination chamber and while onion seeds will sprout without light, I recommend setting them in a well-lit place (or under your grow lights) so that the shoot side will photosynthesize and you can tell which side is up or down. Check your seeds every few days.
•Once you notice a little shoot emerging from the seed, wait another day or so- no longer.
•Fill the seed tray to with MOIST homemade seed starting mix, and tamp it down with your fingers. (If you don’t tamp it, the soil will settle over time and your roots will be exposed.) Top off the flat with more soil, but this time don’t tamp it.
•Gently grasp the seed and gently insert it root-down into the soil. Sometimes it will stand, sometimes it won’t. That’s ok. If they get covered up a bit that’s ok too, they’ll emerge in a day or two.
• Onions are heavy feeders and they will be in this space for quite a while, pulling up nutrients out of the soil mix. Don’t space them too closely. I plant 4 to every 1 square inch.
•Sprinkle a very thin layer of vermiculite on top. This will help to prevent damping off disease.
• Sometimes I will have a few where the root was exposed after a week of growth and I gently bury that portion. If you have any that grew in upside down, or very crooked and I re-planted them, so to speak, to adjust them properly.
•Fill the seed tray to with MOIST seed starting mix (this is my favorite homemade mix recipe) and tamp it down with your fingers. (If you don’t tamp it, the soil will settle over time and your roots will be exposed.) Top off the flat with more soil, but this time don’t tamp it.
•Sprinkle a very thin layer of vermiculite on top. This will help to prevent damping off disease.
• Onions are heavy feeders and they will be in this space for quite a while, pulling up nutrients out of the soil mix. Don’t space them too closely. I shoot for 4 to every 1 square inch, but since germination won’t be 100%, I will sow an extra 2 or 3 per square inch to make sure there is no wasted space and if they all germinate, I will remove them later.
•Do not just broadcast seeds across your flat. Yes, these other 2 methods are labor intensive, but I promise you, you are going to regret not taking the time later in the year when your onion seedlings are a thin, scraggly, tangled mess and you’re breaking them during transplant trying to get them apart.
• Once the onion seedlings are established and growing well, you’ll notice that they will start to droop. From that point on, they’ll need to have their “hair cut” about once every 7-10 days. Keep them trimmed to about 2-3 inches so that they’re busy building a good root system.
•Keep them watered well, but don’t overwater. Although I have known them to be forgiving.
• Because onion are heavy feeders, you’ll need to fertilize them. I use cold-pressed fish emulsion. It’s going to smell for a couple days. It will subside, I promise. Do this once a month.
•Remember to harden them off prior to transplanting. You can begin the process indoors, by simply brushing your hands over the tops daily. You’ll definitely notice them becoming stiffer. About a week or two before transplant, take them outside during the warmest time of the day for a few hours. Increase the amount of time spent outdoors each day until they’re outside 24 hours for a day or two before transplant. Trim the tops once more before transplanting.
•Prepare the site by loosening the top couple inches of soil. If you have heavy clay, I suggest you mix in some sand in the top few inches as onions do well with good drainage and loose soil.
•If you plan to use mulch to suppress weeds in your garden, do so before transplanting. It’s easiest to lay down the mulch in the bed and then open up a space to plant the onion into. It’s quite difficult to lay mulch around onion seedlings.
• You have several spacing options to consider when planting onions. Which you choose depends on your garden space and how you plan to manage weeds.
Planting onions staggered on the diagonal allows for closer spacing (and higher yields).
Two per hole
Plant 2 seedlings per hole and then harvest one early, while they’re still small, harvest the second at maturity. A great way to extend your harvest season!
Four per hole
In The New Organic Grower, Eliot Coleman shows a method of planting onions where 4 onions go in each hole. If you planted 4 seedlings per 1″ pot, that makes transplanting a breeze. We tried this method last year and they grew just as well as those in a staggered row.
Single Row, Interplanted
One method is to plant single plants in a row and then instead of keeping the row weeded, interplant a quick growing crop like arugula or radishes, both of which are ready to harvest in about 30 days.
•Keep them watered regularly, without overwatering, until the tops begin to die off and then cease watering.
•Continue to fertilize with fish emulsion once a month throughout the growing season. If the leaves begin to yellow, you need more fish emulsion. I make sure to use my Homestead Management Binder to keep track of when I need to do jobs like this. If I don’t, I will forget to do them altogether or can’t remember when I’m supposed to do it again.
•Onions hate competition from weeds. I’ve used old hay mulch to suppress weeds and it really makes weeding a breeze.
• If you’ll be enjoying your onions fresh, then you can begin to harvest at any point after the bulbs have developed.
• For onions that will be in storage for any length of time, watch for their tops to begin to bend over and die off. This is your cue that they’re about ready to harvest. If you find that most of your onions are dying off and you don’t want to drag the harvest out over time, you can bend the tops of the green ones over towards the ground and they’ll all cure about the same time.
• If your bulbs are mostly buried when the tops begin to die back, gently pull the bulbs partially out of the ground. Brush the soil away from the top 2/3rds of the bulb.
•If you’re experiencing a wet summer and are worried about your onions rotting, you can pull them early and cure them in a greenhouse, barn, or shed, though they might not keep as long in storage.
Curing & Storage
•Once the tops have mostly dried, harvest the crop and place them in a warm dry place to cure. We’ll put a cheap box fan on them to increase air circulation. It might seem like a lot of work, but it’s worth it to make sure they keep in longer in storage.
•Allow about 2 weeks for the tops to completely die off and dry out and then trim them off about 3″ above the crown.
•Store cured onions in a dark place, just above freezing temperatures.
•If your onions begin to sprout, you can always preserve them by caramelizing them and canning them in a pressure canner.
Do you have a favorite onion that you grow?