ONIONS – High Country Living

ONIONS & SHALLOTS

Onions & shallots* are a big deal for me & my garden. I can’t really do without onions. Onions for everything: soups, stews, casseroles, sauces, salads, sandwiches, eggs & quiches, you name it. The onions I had grown in our previous garden (5,200′) all did wonderfully. I had no reason to believe they would not do well here at 9,000 feet. I’d read on a local county resource list that other gardeners had success with some of the same varieties I’d grown before, so I thought onions should be easy to grow and as I started the garden that first year here I expected success. My, oh my. I was in for a few years of trial & error & error & …. Well, you get the idea. Every year onions have gotten better & better until this year–2025–has been a banner year for onions. The best ever!

Onions require extra time and care but can grow quite successfully. My best results have been from starting seeds indoors (in soil blocks) up to 20 weeks prior to my last frost date. They are transplanted into my greenhouse beds a couple of weeks later, then they’re transplanted outdoors about 3-4 weeks before the last frost date when they are at least the size of an icepick. Starting later & transplanting smaller onion seedlings will result in smaller bulbs. Choose onion varieties appropriate for your latitude. “Intermediate-day” do best in Colorado. I have also had good success buying onion transplants ready-to-plant, however it is much less expensive to grow them yourself.

*Onions & shallots are grown from seed the same way. Throughout this document, when I speak of growing “onions”, consider this to include shallots.

For more detailed information on how to grow onions & shallots at high elevation, see below.

ONION GROWING TRIALS

The first year I l was gung-ho and planted around 40-50 onions using the same method I’d used at 5200′. I started the onion from seed indoors in soil blocks the first part of April and transplanted them outdoors mid-May. All I got for my efforts were a few bulb-less, fat green onions. I realized I needed to come up with a better plan!

Over the years since then I’ve tried several different experiments:

- I tried planting seeds in the ground in the fall. Some of these did fairly well. I was rewarded with some small, but decent bulbs. Not all that I’d planted survived.
- I tried “overwintering” onions by starting overwintering varieties from seed around 8/1 to grow to bulbs in the spring. These grew to a bit less than the size of an ice pick spike by mid-September. They were mulched well for the winter, but all died before the following spring. Perhaps these would have lived if started sooner in order to get larger onions before winter set in, or if they were given better protection over the winter. However, I’m not optimistic that this would work.
- I ordered some onion plants for transplanting from Dixondale Farms in Texas. I followed their planting instructions exactly and used their fertilizer, which I don’t believe was organic. 🙁 These were the best onions I’d grown here to date.
After the success I’d had with the onion plants I’d ordered, I thought, “I can grow onions to this size myself, from seed.” I now start onions mid- to late-January under lights. I transplant them to the the greenhouse beds after they’ve grown an inch or two. By mid-May these healthy, small plants are about the size of an icepick, the same size as the Dixondale plants I’d ordered previously. These are planted outdoors mid-May, about 4” apart in rows 15-16” apart, with a trench between the rows filled with starter fertilizer & bone meal at planting and occasionally thereafter. This is my best (and cheapest) method yet!

HIGH ELEVATION GROWING TIPS:
ONIONS & SHALLOTS

(GROWN FROM SEED)

Choose day-length seeds specified for your latitude.
Save the date: Plan to transplant your onions about 4 weeks before your “last frost date”. (This may change due to weather, but save the planned date.)
Start seeds indoors early, about 18-20 weeks before your planned transplant date
Keep the onion tops trimmed to about 5-6” tall as they grow.
About a week prior to your transplant date, begin to prepare your outdoor soil (raised beds or in-ground) by adding 1-2” compost and an all-purpose vegetable fertilizer. Use a little less fertilizer than what the product recommends.
Transplant outdoors 3-4 weeks before your “last frost date”, when onions are at least the width of an icepick spike. It’s ok to be a bit flexible depending on the weather forecast. If some of the onions aren’t as big, go ahead and plant them. They may grow a bit smaller than the others, but at least you’ll have an onion.
Before bringing your onions out to the garden, prepare your garden bed. The onion seedlings will be planted about 4” apart, in rows 15-16” apart
Optionally, dig a trench about 4” deep between the rows to be filled with fertilizer. If using the trench method, fill it with an organic fertilizer especially formulated for onions. This should be 10-20-10, or something relatively high in phosphorus. If you don’t have that, add some extra bone meal, kelp meal or greensand to the trench. For more information about using this trench method (with a diagram) see: Dixondale’s ONION PLANTING GUIDE.
If not using the trench method, you can add those fertilizers to the ground between the onion rows, digging it in as much as you can. I have found this method to work as well as the trenching method in my home garden raised beds.
Carefully remove onion transplants from your greenhouse beds or trays used to start the seedlings just before planting.
Plant the onions as stated above, about 1″ deep.
Water onion transplants right away.
If snow or a deep freeze is expected soon after transplant, protect onions with frost cloth suspended above them like a tent, or with plastic stretched across hoops over the onions.
Keep them watered regularly. Generally, check the soil with your fingers. If it becomes dry a couple of inches below the surface, water the onions.
Every 3-4 weeks, add a fertilizer high in nitrogen to the trench, until they begin to “bulb”.
Keep onion plants free from weeds.
If any onions begin to bolt, cut off flower stalks as soon as possible. Plan to eat these onions first; they won’t store as well.
Harvest onions after their tops turn brown and/or bend over. If a deep freeze or snowstorm or a lot of rain is predicted, bend over the tops a few days in advance, and harvest prior to the storm. Onions will not be damaged with a few light frosts.
Cure onions indoors if it will be below freezing outdoors. A greenhouse or non-freezing garage or basement will do. Keep the tops bent over and lay them on an airy rack or hang them from a wire or rope stung across your curing area.
When the necks become dry, cut off the leaves about 1″ from the onion. Lay them on a rack and allow the top to dry out completely before putting them in long-term storage.
Store onions in a root cellar or other cool, dark, well-ventilated location, preferably between 32-40°F.

ONION STORAGE & PRESERVATION

After curing (above), we store onions in the upper section of our Cold Closet. The upper section is a bit warmer and dryer than the main part of the closet, with ventilation provided by holes in the outer walls. It is usually in the 40°F range throughout the winter months. The onions generally store nicely until the following spring.

If you’ve grown more onions than you will eat before they begin to go bad, they can be diced & frozen or freeze-dried for longer preservation. There is no need to blanch onions prior to freezing or freeze-drying.

ONION VARIeTIES GROWN

ONIONS THAT DID NOT DO WELL
Oneida (F1) | 105 Days | Intermediate Day – These were shown as “Intermediate-Day” on the Territorial Seed website, but they did not bulb out in my location. Other websites indicate that these are “Long-Day”.
Gladstone (F1) | Intermediate Day. These mostly bolted and did not do as well as the other onions (2025).
Clear Dawn (OP) | 104 Days | Long Day – Some were good, but these had a 50% chance of forming a bulb in this location.
Dakota Tears (OP) | 112 Days | Long Day
Red Amposta (OP) | 115 Days | Intermediate Day | These were “just okay”.
Figaro Shallot (OP) | 125 Days | Long Day. Did not produce many good bulbs.