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Why you’ve got to try it?!

For the love of onions + self sufficiency

I don’t know about you but I love onions! Well, I practically start every meal with them, fact that caused my husband some shock. I was of course, more shocked that he had none, zero, zip in his house!!!!  I can’t think of a lot of crops that are more rewarding to grow yourself.

Now, I know a lot of you may purchase onion sets. Over the years we have also done this, with very hit or miss results. I always found myself  disappointed and was more sucessful when I started growing onions from seed.

Some of the benefits include:

1) Healthier starts that take right off in the garden and actually bulb up! 

2) More options of varieties and the ability to choose the correct day length for your area. Support maintaining onion diversity. 

3) It’s so rewarding to start from seed and end up with a cellar full of onions, that will last you until spring.

In this article we will share our 5 tips for success to get your onions started from seed.

The rare and beloved Bronze di Amposta onion

Onions are loved worldwide

I am not the only one who loves onions. They are one of the most ubiquitous agricultural crops in the world and almost all culinary traditions use them. Onions were domesticated about 3,000 – 4,000 years BCE originating from the steppes and mountainous regions of Central Asia. Now they are grown from subarctic to the tropics. There is an incredible diversity of onions that have existed across the world. However, this is being threatened by the dependence on hybrids in modern agriculture. Thus, the number of people maintaining many of the diverse, open pollinated varieties is decreasing rapidly.

Onions are day length sensitive, meaning the hours of daylight (or photoperiod) an onion receives, triggers the onions to begin sending starches and sugars into the bulb, leading to a nice plump onion. Different varieties have different requirements. In general onions are broken into three categories; long, intermediate, and short day onions. That being said, it is important to pick a variety that will bulb up properly for you. This depends on how many daylight hours you receive.

  • Short-day onions require just 12 to 14 hours of daylight each day to form bulbs.  No greater than latitude 36°N.
  • Intermediate-day onions require 13 to 15 hours of daylight each day to form bulbs. Between latitudes 35° to 38°N–but many are adapted for production to latitude 42°N.
  • Long-day onions require 14 to 16 hours of daylight each day to form bulbs. Best at latitude 36°N or above.

We have seen a sharp decline in commercially offered intermediate-day onion varieties available, but are working to keep some of these varieties around. 

Onion starts growing directly in the ground

When and How to start Onions Indoors.

It is important to start onions early. We seed them the last week of January through mid- February, here in zone 6b, giving them as much time as possible to size up before transplanting. Alternatively, we have also heard of sowing onions directly into the garden in the fall. This is an especially common practice with intermediate day onions. In this context, we are going to talk about starting them indoors.

What you will need:

First you will need a good potting soil that is formulated for use in containers. We recommend mixing in a few handfuls of native soil. Onion roots have a strong relationship with arbuscular mycorrhizal(AM) fungi that are present in most soils. Adding a little native soil will inoculate your mix with those fungi, leading to larger, more robust starts. This is something we have figured out after growing onions in soil medium for many years and then switching to starting onions directly in the bed of our greenhouse. We were amazed because the plants grown directly in the ground were so much more hearty and robust. It’s all because of symbiosis with the AM fungi!!!!

Pick a container to grow your onions in that has drainage but is not too porous. You will be growing these starts for up to 11-14 weeks, so it is important to pick a container that can hold up. These could be old salad containers, tupperware, or a starter tray. Just make sure to punch some drainage holes in the bottom of the container and ensure it will drain. (Caution: please do not use egg cartons or you risk dessicating your seed babies).

Start with fresh seed, as onions have a relatively short window in which they are vigorous and viable (look at the pack for date on your seed packet to ensure they are 1-2 years old). Make sure to pick a variety that is the correct day length for your latitude. For example: here in Colorado we are about 38°N in latitude meaning intermediate day and short day onions will be best for this region. 

Sow seeds shallowly in rows or broadcast (aka sprinkle) across your container with approximately 1/4” between seeds. Cover your seeds lightly with a layer of potting mix. Keep them in a warm environment, 60-70 degrees, in a place with good light. Preferably a south facing window. If you have a heating mat, that will greatly aid germination but is not necessary. Just keep in mind that without a heat mat germination may take longer.

Keep evenly moist until germination, but remember to let them dry down some between waterings. In other words, they should not be constantly soggy or they will not germinate well and may even rot. We will sometimes cover them loosely with a piece of plastic or plastic domes until we see them start to germinate. This creates a greenhouse-like environment, keeping them warm and consistently moist, allowing us to almost forget about them until we see germination. 

As they start to grow, let the plants get to about 4-6” tall and then give your onions a haircut. Yup, they need haircuts too!  Really! Cutting them back to about 2” will stimulate the plant to start putting more energy into the bulb and filling out.

Baby onions after their first haircut!

Your onions will be ready to transplant in the garden when they are about pencil thick (though it doesn’t matter if they are smaller than that). Once your plants are ready and it is time to plant,  it is important that you harden off your plants for at least a week before planting. Your onion starts should be transplanted out only after the last hard frosts are over. They can take light frost, but baby onions can be killed or damaged by hard frosts. Transplant your onions out between 8-10 inches apart depending on how big the variety will ultimately be.

Prepping onions for transplant.


Here are our 5 tips for success: 

  1. Start with fresh seed, as onions have a relatively short window of vigor (look at the pack for date on your seed packet)
  2. Make sure you have the right seed for your latitude (daylight hours)
  3. Mix in a little native soil with your starter mix to ensure the microbes are present.
  4. Keep evenly moist until germination (try the covering trick)
  5. Give em’ a couple of haircuts 


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