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Today I am excited to share with you how to start onion seed indoors in January! I hope you will pick up some helpful tips and tricks, and learn how we grow enough onions to use for most of the year!
Today I will go over when and how to start onion seed indoors step by step! Starting onions from seed is not difficult at all. By starting onions from seed, you will have many more varieties to choose from.
When to Start Onion Seed Indoors in January
January is the month my fingers get itching to plant onion seed. Luckily there are a few things you can plant by seed as early as January here in the PNW, even earlier in milder parts.
Onion seed is usually the first thing I plant in the dead of winter. Other things that may be started this month by seed are celery, artichoke, asparagus and hot peppers.
How to Store Onions from the Garden
How to Plant Onion Seedlings.
Seed Starting Schedule for Garden Zone 8b
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Different Methods for Sowing Onion Seeds
I sow most of my seeds using two methods, Winter Sowing and also indoors using your standard seed starting Equipment. Please see these two article for more information on both methods:
Seed Starting 101: Winter Sowing in which I share how I use milk jugs outdoors as mini greenhouses to start seed. Winter sowing is a great option for starting onion seed if you don't have a lot of room indoors. Plant the milk jug with the seed as set it outside, simple as that.
Watch for the seeds to germinate, and you can open the lid and leave it open once the seedlings need their first trim, (see below for more info on that!). Onion plants don't mind the cold once they have germinated, but I might still bring them inside if it gets below freezing.
Seed Starting Equipment lists more details about equipment needed to start your seeds indoors. It also covers what type of soil I use for starting seeds. I will go over how I plant onion seed indoors using this equipment set up in more detail down below.
Choosing Which Onion Varieties to Plant
I chose several varieties of onion seed to plant, with my primary focus being on onions that are excellent keeping onions or also called storage onions. These types of onions will last in storage all through winter after harvesting and curing them.
Sweet onions like Walla Walla and Vidalia are delicious, and I usually grow a small amount for fresh eating. But if you want to keep onions for a long period of time, these are not the best for that.
Onion Seed vs Onion Sets
When trying to grow most of our own produce for the year, it is essential to look at varieties of food that keep well. For this reason, I choose not to start my onions by onion sets.
Often onion sets will bolt very early, as they are actually onion that was grown from seed the previous year. Their main objective is to reproduce, so all their energy goes into making seed, not into making a large onion bulb.
There are usually not many varieties to choose from when using onion sets either. By planting from seed, you can plant any varieties of onions including leeks, shallots or heirloom varieties using the process I outline below.
Storage Onions aka Keeping Onions
This year for storage onions, I will be growing Talon, Cortland and Red Bull F1. I have grown all of these before and they have all grown well for me. Other varieties that I have grown that have done well for me are Patterson and Red Wing.
The Red Bull kept the longest in storage before sprouting, so I always grow a lot of it, even though we prefer the yellow onions.
The Walla Walla's are a sweet onion, and will only be used for fresh eating.
Viability of Onion Seed
Onion seeds are one type of seed that do not store well. I learned that the hard way one year. I planted 2 yr old left over seed, and had less than 10% germinate.
Now I always buy fresh onion seed as a result. So be sure you are using fresh seed. If in doubt how old the seed is, buy new. I would not get onion seed from a seed swap for this reason.
Long Day Onion vs Short Day Onions
When you plant onion seed, be sure you are choosing the correct onions for your area. There are long day onions which do best in the northern half of the states and need daylight for longer than 12 hours a day. Then there are short day onions which do better in the southern half of the states and require less sunlight hours during the day.
How to Start Onion Seed Indoors
For planting onion seed, I like to use seed tray inserts that are approximately 4" x 6" or 5"x5". Draw 4 furrows about a ½" deep the length of the tray. Plant the onion seed down the line, maybe 1 seed every quarter inch or so. I use a chop stick to help place them.
You could also use 4" pots and just sprinkle about a ½-1 teaspoon of seed on top and cover gently with soil. Don't be worried about planting onion seed too close together.
There is no need whatsoever, to plant one or two seeds per each little cell pack if you are using 6 packs, throw 6-10 seeds in each cell. Once the plants are mature, it is easy to pull them all apart and they don't mind being snuggled up close.
Than gently cover the seed with soil and press down all the soil in the tray firmly with your palm and fingers. Spray with water, enough water to get the top inch or so of soil damp.
Place in a standard size plant flat without drainage holes. When the flat is full of seed trays, cover with a plastic humidity dome or saran wrap.
These would probably germinate fine without a heating mat as the ideal germination soil temperature is 55-75 degrees. But I have seed mats on hand so I place the flat on the heat mat when done.
If you don't have a heat mat, try placing the flat in a warm area such as on top of the refrigerator. Watch that the soil doesn't dry out, and spray when necessary to keep the seed in a damp soil medium.
Caring for the Onion Seedlings
Once the majority of the seeds have germinated, it is safe to take the plastic dome lid off. This is only used to ensure that the soil stays damp for germination.
From this point onward, water from the bottom, by filling the flat about halfway with water. Onions are heavy feeders, so I like to feed them with Fish Emulsion Fertilizer in the water, using a highly diluted amount of 1-2 TBSN's per gallon of water.
It is a good idea to place a gentle oscillating fan pointed at the seed starts. This helps prevent mold and fungus from growing on the top of the soil which can harm the plants. It also helps to create a stronger stem on the plant.
At this point, they can also be taken off the heat mat if you are using one. Onions don't mind the cold, and it will free up your heat mat for growing another crop that needs it like tomatoes or peppers.
Ideally the plants should also be under grow lights, placed about an 1" above the plants, raising the light as needed to stay close to the tops of the plants.
I keep them under the grow lights for the first few weeks, and then if you live in a mild enough climate like I do, they can move outside in a sunny sheltered area if warm enough. Just watch the weather and bring them in if it gets to freezing or below.
Trimming your Onion Seedlings
As your onions starts grow, they may get long and scraggly. It is perfectly ok to give them a "haircut" to neaten them up. I trim them down to 2-3" high.
Trim them pretty regularly, every few days or at least once a week. When the plants are flopping over on top of themselves, they don't get as much air circulation which is unhealthy for them and will cause rot.
Preparing your Onion Seedlings for Final Transplant
Keep watering, feeding and trimming them until you are ready to plant out in the garden. This is usually around April 1st or so here in the PNW. Ideally they should be as thick as a pencil, but I have planted them when thinner. Ideally they should also have their third "leaf" in.
If it is going to be really wet out, I suggest waiting as the smaller plants may rot if it is too wet out. Also, be sure to harden the plants off over a week or so, as they slowly need to adjust to living outside. Putting them straight in the garden without hardening them off, will put them into shock which is not good.
See my article on How to Harden Off Your Seedlings.
See more information on How to Transplant Onion Seedlings.
Don't forget to consider other onion plant family varieties when you plant onion seed. You could also start leeks, chives, white onions, Spanish onions, or choose from a vast assortment of heirloom onions.
Want to Remember This?
As you can see, it is not that difficult to grow onions from seed! I hope this help you understand how to start onion seeds indoors and the benefits from doing so, and that you can grow some unique to you varieties of onions this way. Happy planting!
Hi Tamara, great looking blog! I'll definitely be following, I love what you've done with your place. Thanks for sharing your knowledge and experience.
Thanks so much Carolyn! I've enjoyed learning from you as well! 🙂
Hi Tamara! My name is Breezy and I live in Anchorage, Alaska. I'm very excited to learn about your winter sowing technique for perennials! This article about starting onions from seed is so well laid out. It makes me feel like even I could be successful at it. I try to grow vegetables every year but I was, unfortunately, not blessed with a green thumb. The only things I'm decent at growing are flowers. I really need someone to teach me so I'm very excited about your blog. Last year I lost all my pepper plants, that had started to bloom beautifully so it gave me hope, to aphids that ate every single one of said blooms. I did get about 10 or so tomatoes even though the plants were riddled with blight because we had way more rain than usual. 10-12 tomatoes is pretty pathetic after all the nurturing and work I put into those plants. Don't even get me started on my mouse-melon endeavor. I am bound and determined to grow enough vegetables to be able to feed my family and to put up for the winter. Someday I will get it right.
Hi Breezy! So glad you found my site! Please feel free to ask any questions you have along the way. My goal is to help people here, so I love questions!!! Today was errand day and clean house day after along weekend away, but I am hoping to have my winter sowing post up tomorrow, followed by a post soon on how I start my tomato and pepper seeds. 🙂 Thanks so much for reaching out and saying hello!
Thanks for sharing Tamara. We tried starting onion from seed once and it didn't turn out well. But I have learned a few things from your post and may try again!
I will be featuring you on my site for this week's Farm Fresh Tuesdays Blog Hop!
Come by and say hi!
Melissa | Little Frugal Homestead
Thanks for featuring me Melissa! I hope you have better luck this time around with your onion seed. Be sure it is fresh seed! Older onion seed doesn't germinate well at all!
I have a few questions. If my last frost date is May 13th, Western PA Here, when should I plant my seeds indoors? I'm expecting to plant my early spring crop carrots, beets, and lettuce (in the ground) around April 15th, 4 weeks before our last frost date for winter. Also does it matter what type of grow light we use indoors? And how long do they need to be under the grow light for?
Thanks so much! - Stephanie
Hi Stephanie, Onions are a cold tolerant vegetable, and are fine to transplant outdoors before the last frost date. Your frost date is about a month after mine, and I start my onions indoors in January, and then transplant them outside in late March or early April. So I would say that you are probably good to start them at the end of this month or any time in February. And then they can probably go outside the same time as your carrots and beets if they are ready. I like them to be at least 1/8" thick or so before moving them outside. They should be under a grow light for the first month or so, and then you can start transitioning them to outside by hardening them off slowly, a little bit each day. I have an article on hardening off seedlings here: https://thereidhomestead.com/how-to-harden-off-your-seedlings/ Once they are all hardened off, and are about 1/8" thick at the base of the plant, then they are good to be planted in the garden. Be sure to give them lots of hair cuts to keep them nice and tidy! And see how I plant them in the garden here: https://thereidhomestead.com/how-to-plant-onion-seedlings/ Oh, as far as grow lights go, I prefer to use cheap shop lights and fluorescent bulbs. You can see more about my indoor seed starting equipment here: https://thereidhomestead.com/seed-starting-101-equipment/ Happy Growing!
Can I start shallots indoors at the same time that i start my other onions?
Hi Beth, YES if starting by seed, you can start all the onion family of plants at the same time. Leeks, shallots, green onions, etc. Happy Planting!