Learn How to Grow Onions from Seed to Harvest

sI’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 start 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.

Onion 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 starting onion seed in the dead of winter. They fan the flame of spring hope early for me and extend the growing season beyond its normal bounds!

Growing 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. Starting onions from seed is 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 whereby I started onion seeds from a variety of cultivars. I could start them all at the same time and but their days to maturity were staggered. So I would have a continuous harvest throughout the season with little worry of storage until the late fall harvest. I’ll use the SmartSteader homestead management app to take notes and track yields when I come up with these ideas to know if it’s really worth it!

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 onions from seed) and I don’t want any wasted space I will “chit” or pre-sprout my onion seeds. It even more important to chit your seeds if they were extra seed in storage from last year.

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 fluorescent 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.

(Me too.)

My yield- zero.

Trial and errors have 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 to Harvest

Seed Starting

Pre-Sprouting Method

• 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. While onion seeds will sprout without light, I recommend setting them in a well-lit place so the shoot 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 starting containers 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 nutrients out of the soil. 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.

• If the root becomes exposed I gently bury that portion. If you have any that grew in upside down, or crooked then re-plant them.

Traditional Method

• 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.

Onion Seedling Maintenance

• 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 “haircut” about once every 7-10 days. Keep them trimmed to about 2-3 inches so that they’re busy building a good root system. Lightly blowing a fan on them will make the leaves stronger and stiffer, but is optional.

• Keep them watered well, but don’t overwater. Although I have known them to be forgiving.

• Because onions 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 transplanting, 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.

Transplanting Onion Seedlings

• Prepare the site by loosening the top couple inches of soil. If you have heavy clay, 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 mulch 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.

 Staggered

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. Instead of keeping the row weeded, interplant a quick growing crop like arugula or radishes, which are ready to harvest in 30 days.

How to Grow Onions

• 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.

How to Harvest Onions

• If you’ll be enjoying your onions fresh, you can begin harvesting at any point after the bulbs have developed.

• For onions that will be in storage, watch for their tops to bend over and die off. This is your cue that they’re about ready to harvest. At this point, bend all of the leaves over to the ground. This will tell the bulb to go dormant, finish maturing, and ripen. It’s an important step to make sure your onions are all ready for the curing process at the same time.

• If your bulbs are mostly buried when the tops die back, gently pull them 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 onions rotting, pull them early. Cure them in a greenhouse, barn, or shed. (Though they might not keep as long in storage.)

Curing & Storing Onions

• Once the tops have mostly dried, harvest the onions and place them in a warm dry place to cure. We’ll put a cheap box fan on them to increase air circulation. Curing onions well will make sure they keep in longer in storage.

• Allow 2 weeks for the tops to die off and dry out 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 seed variety that you grow? 

 

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