Onions 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.
The first year I planted around 40-50 onions using the same method I’d used previously. 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 small, but decent bulbs.
I tried “overwintering” onions by starting overwintering varieties from seed around 8/1 to grow to bulbs in the spring. These grew to about the size of an ice pick spike by mid-September. They were mulched well over for the winter, and all died before the following spring. Perhaps these would have lived if started sooner to get larger before winter set in, or if they were given protection over the winter. However, I’m not optimistic that this would work.
I tried planting a few for overwintering in our cold frames, but they succumbed in the cold.
I ordered some onion plants for transplanting from Dixondale Farms in Texas. I followed their planting instructions exactly and used their fertilizer. 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 in the greenhouse. By mid-May these healthy, small plants are about 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 fertilizer & bone meal at planting and occasionally thereafter. This is my best (and cheapest) method yet!
ONION HARVEST
High-elevation onions take longer to grow than those grown in warmer locations. I keep them in the garden as long as possible, harvesting after they’ve begun to bend over, usually in September. Sometimes I’ll need to bend over the tops to get them out of the ground prior to a predicted snowstorm. The onions are cured in the greenhouse by hanging them over some fencewire.
Fall frost does not damage the onions unless it is extremely cold. My onions are generally harvested between 125-140 days after transplant to the garden, and this is after they’ve grown about 100 days in the greenhouse.
I’m growing onions 8 months out of the year here, 225-240 days in total. For me, it’s worth that commitment. Onions I buy from the store do not last very long. I believe that once they come out of their cold storage to sit on the grocery store shelf where it’s warmer, they come out of dormancy and want to grow. Growing & storing your own onions allows them to keep much longer.
ONION DAYLENGTH
Some words about day length. We are located at latitude 38.77. The best day length here for onions is “Intermediate Day”. It is important to know the day length for your own latitude. I have attempted to grow some Long-Day onions here, but they haven’t produced many bulbs, if any. A good day-length map can be found at Dixondale Farms. Most seed companies will indicate the day-length or best latitudes for growing each variety. If not, do some additional research. You really DO NOT want to end up with an entire row of immature onions at the end of your growing season! Bulbless onions can be used, but they do not store very long. The best bet for storing these is to freeze-dry or freeze the diced onions.
HOW TO GROW HIGH-ELEVATION ONIONS
Choose day-length seeds specified for your latitude.
Start seeds indoors early, at least 14-15 weeks before transplanting outdoors, about 18 weeks before your “last frost date”, in greenhouse beds, trays, or soil blocks. For me, the onions are best when started January 15-31.
For the best success, start the onions in soil blocks, then transplant them to the greenhouse before taking them outside.
Trim the onions occasionally to about 5-6” tall while they’re growing indoors.
Plan to transplant the onions outdoors 2-3 weeks before your “last frost date”, preferably when onions are at least the width of an icepick spike. Some freezing nights shouldn’t hurt them, but be prepared to cover them with frostcloth for extra protection.
Onions in Greenhouse Bed, Ready to TransplantPrior to planting outdoors, prepare your soil (raised beds or in-ground) by adding 1-2” compost, an all-purpose vegetable fertilizer and bone meal. Use a little less fertilizer than what the product recommends. (More will be added later.)
Carefully remove onion transplants from your greenhouse beds or trays used to start the seedlings just before planting.
Onions should be planted about 4” apart, in rows 15-16” apart, with a trench about 4” deep between the rows to be filled with fertilizer.
Fill the trench with an organic fertilizer especially formulated for onions. 10-20-10, or something relatively high in phosphorus. Use a little less than the fertilizer recommendation, since you already added some in the step above.Onions Growing in Raised Bed, Trench in Center
Water onion transplants right away and keep them watered regularly.
If snow or a deep freeze is expected, protect onions with frost cloth suspended above them like a tent, or with plastic stretched across hoops over the onions. A little snow shouldn’t hurt them after they’ve been in the ground a couple of weeks.
Every 3-4 weeks, add a fertilizer high in nitrogen to the trench.
Keep onion plants free from weeds.
If any onions begin to bolt, cut off flower stalks as soon as possible. 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 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. Please refer to another resource for how to cure your onions.
After curing, store onions in a root cellar or other cool, dark, well-ventilated location.
Onions Hanging to Cure in Greenhouse
ONION STORAGE & PRESERVATION
After curing, 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 40-50 degree range. 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.
ONION VARIeTIES GROWN
FAVORITE VARIETIES: All have done well in this location. Expression (F1) | 98 Days | Intermediate to Long Day – One of the best Almagro (F1) | 100 Days | Intermediate Day – These did well in 2024. Monastrell Red (F1) | 110 Days | Intermediate Day Cabernet Red (F1) | 90 Days | Intermediate Day Candy | 90-100 Days | Intermediate Day Superstar | 95 Days | Intermediate Day Red Candy | 85-95 Days | Intermediate Day Figaro Shallot (OP) | 125 Days Conservor Shallot (F1) | 110 Days
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”. 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”.
High-elevation onions take longer to grow than those grown in warmer locations. I keep them in the garden as long as possible, harvesting after they’ve begun to bend over, usually in September. Sometimes I’ll need to bend over the tops to get them out of the ground prior to a predicted snowstorm. The onions are cured in the greenhouse by hanging them over some fencewire.
