- Author: Help Desk Team
If you've been frustrated when growing onions because the plants produce flower stalks instead of bulbs, it is time to try again. In our Contra Costa County climate, when onions are started in the fall, it is not unusual for them to flower the following spring. After flowering, the onion plants cannot produce a good bulb for harvest. To avoid this result, plant your onions in February.
Onions are biennial plants meaning that they should grow for two years before flowers develop to produce seeds. To understand why premature flowering occurs for onions planted in the fall in our climate, it is helpful to understand two aspects of onion growth—the requirement for long periods of daylight for bulb production and vernalization which is exposure to cold temperatures that triggers flower production.
Depending on the variety, onions need between twelve and sixteen hours of daylight to produce bulbs. Contra Costa County has twelve hours of daylight by early April and about fourteen hours and forty-five minutes of daylight by late June. Consequently, depending on the onion variety, bulbs will not start to develop until late spring or early summer.
Vernalization is a botanical process that induces a plant's flowering production to occur following exposure to cold temperatures. When onions are planted in the garden in the fall in our climate, they can mature quickly. If onion stalks have grown to at least the size of a pencil while fall temperatures remain warm and are then exposed to cold nighttime temperatures in December or January, vernalization occurs. When temperatures begin to warm in early spring, flower production is triggered. Since daylight hours are still too short to produce bulbs before flowers form, the result is an onion plant that grows flowers but will never produce a bulb.
Try planting your onions in February to avoid vernalization. In our climate, if seedlings are planted in February, they are unlikely to encounter nighttime temperatures cold enough to induce vernalization. Without vernalization, flowers will not develop prematurely and good size bulbs can develop as soon as there are sufficient daylight hours.
When starting onions in February, it is best to transplant seedlings into the garden bed rather than placing seeds directly into bed. Using seedlings makes it more likely that the plants will mature sufficiently to allow bulbs to form as soon as daylight hours are sufficiently long.
If you want to plant your own seeds, start them indoors in December so that the seedlings are ready for transplant by February. Keep in mind that onion seeds only remain fully viable for one or two years so always use fresh seeds. If you haven't yet started your own onion seedlings, look for them in local nurseries.
Avoid using onion sets if you want onion bulbs. Onion sets are small onion bulbs that grew the prior season and were harvested and allowed to dry. When you plant them, the plant that grows will be in its second year of growth and will be ready to produce flowers even without vernalization from cold temperatures.
This video produced by the UC Master Gardeners Program in Santa Clara County shows how to transplant onion seedlings into the garden and explains how to harvest the mature onion bulbs: https://www.youtube.com/watch?v=Gb1WhqtsdMI.
For additional cultural tips for onion production, see this UC website: https://ipm.ucanr.edu/home-and-landscape/onions-and-garlic/cultural-tips/index.html?src=307-pageViewHLS
This UC website will help you manage onion pests and diseases: https://ipm.ucanr.edu/home-and-landscape/onions-and-garlic/index.html
Help Desk of the UC Master Gardeners of Contra Costa County (TKL)
- Author: Vivian Patterson
I love Bread & Butter Pickles! One of the things I love best about them are the onions. We have just harvested our onions but don't have our cucumbers yet. I decided to make a version with just onions.
Step by Step Preparation for Bread & Butter Style Pickled Onions
Adapted from Ball's "Red Onions in Vinegar" recipe.
2½ - 3 pounds Onions, thinly sliced
¼ cup Kosher Salt
½ gallon cool water
- Weigh, peel and slice the onions.
- Cover the onions with a brine of the Kosher Salt dissolved into the ½ gallon cool water. Crack a tray of ice over the top and set aside for 2 hours. Stir from time to time, turning over the layers.
- Make the Vinegar syrup: Combine the following ingredients in a saucepan. Bring to a boil, then remove from the heat and set aside.
½ cup Water
1 ½ cups apple cider vinegar
¾ cup brown sugar
1 ½ tsp. ground turmeric
1 ½ tsp. mustard seeds
½ tsp. celery seeds
½ tsp. coriander seeds
1 ½ tsp freshly grated ginger root
1 small fresh or dried red chiles, diced
- Prepare jars, lids and rings.
- Drain the brined onions and rinse them with fresh water. Bring the vinegar syrup back to a boil, add the onions, and cook for 5 minutes.
- Using a slotted spoon, divide the onions among the prepared pint jars, then ladle the syrup into the jars, leaving ½ inch headspace. Seal, and process in a water bath or steam canner for 10 minutes (sea level.)
Altitude Adjustment—Increase Processing Time:
1,001 – 3,000 feet: Increase by 5 minutes
3,001 – 6000 feet: Increase by 10 minutes
6,001 – 8,000 feet: Increase by 15 minutes
Over 8,001 feet: Increase by 20 minutes
- Check that jars have sealed then clean jars, label, and prepare for storage.
Notes about this recipe:
I sliced 3 lbs. onions, but I only used about 2½ lbs.
Yield: 3 pints.
Although this recipe used spices from a recipe in Saving the Season by Kevin West to obtain the bread and butter pickle flavor, it is essentially the same as the "Red Onions in Vinegar" tested recipe in Ball's Complete Book of Home Preserving with safe additions of salt (as brine), sugar and spices, but substituting 5% apple cider vinegar for red wine vinegar. Not all substitutions are safe to can. If you don't know what can be done, contact the helpline at immg@ucanr.edu, or just refrigerate your custom creation instead of canning it. More information about canning pickles as well as good recipes is available at this site.
Editors note: The Master Food Preservers have a demonstration plot at the Bishop Community Garden. They use the produce from that garden to share safe food preservation practices. As many readers of this blog may have onions ready in your garden, this may be of interest to you. If you have questions about home food preservation, please send your questions to the helpline: immg@ucanr.edu. To learn more about raising onions in the Eastern Sierra this this fact sheet: https://ucanr.edu/sites/
- Author: Vivian Patterson
I have a small growing area at the side of my house in Bishop that gets lots of heat and very little sun. I started planting onions in this area about 10 years ago but found that the bulbs never got more than 1-2” in diameter. Now I intentionally plant onions there every January that I freeze whole.
Here is my process.
After the onions have been picked, dried, & cleaned up, separate into groups according to size.
Peel onions keeping sizes separated.
Blanch Onions for 3 minutes. (Here is how to do this.)
Drain and Prepare to Individually Freeze, Freeze until frozen solid. Overnight is good.
When frozen, remove from freezer. Label Bags. Put desired portions into bags.
Seal all bags. Remove air before sealing.
Notes about Frozen Onions:
- Frozen Onions should only be used for cooking. They are no longer used raw.
- Very small frozen onions may be used in recipes calling for frozen pearl onions.
Uses for Frozen Onions:
- Stews*
- Roast Meats*
- Boeuf Bourguignon*
- Coq au Vin*
- Braised as a side dish (https://www.food.com/recipe/braised-onions-a-la-julia-child-148656)
- Sauteed as a side dish
- Soups
*Braise your onions first. See braised Onion recipe link. Always thaw your onions before braising.
Editor's Note: The Master Food Preservers have a demonstration plot at the Bishop Community Garden. They use the produce from that garden to share safe food preservation practices. As many readers of this blog may have onions ready in your garden, this may be of interest to you. If you have questions about home food preservation, please send your questions to the helpline: immg@ucanr.edu. To learn more about raising onions in the Eastern Sierra this this fact sheet: https://ucanr.edu/sites/
- Author: T. Eric Nightingale
By T. Eric Nightingale, U.C. Master Gardener of Napa County
Until recently onions were, for me, a smelly vegetable I liked to put on hamburgers. I have recently learned, however, that they have a much more colorful history. Despite their checkered past, many people today credit onions with near-magical abilities.
A little online research will turn up dozens of sites proclaiming the health benefits of onions. Among the purported benefits are lower risk of cancer, heart disease and hypertension; better maintenance of blood sugar; and an enhanced immune system. While these claims have varying degrees of verifiability, one thing is certain: people love onions.
Claims regarding the power of onions are nothing new. Onion cultivation goes way back, about six thousand years or so, and likely began somewhere in Asia or northern Africa. There is evidence of onion obsession in almost every civilization and situation possible.
Onions have been used to treat a variety of medical ailments including indigestion, blisters and even dog bites. They were thought to make warriors stronger and to induce romantic feelings, and they were sometimes used as a currency to pay rent.
Ancient Egyptians held onions in high esteem, believing their concentric rings symbolized eternal life. Artifacts found in tombs appear to be onions fashioned from gold.
On the more practical side, onions were easy to grow, transport and store, making them an ideal food for people in a variety of climates. They quickly spread around the world and became a staple of many cuisines.
Onions are a great source of vitamins C and B, potassium and fiber. Researchers investigating the onion's cancer-fighting abilities have focused on quercetin, a type of antioxidant contained within the onion bulb.
When most people speak of onions, they are usually referring to Allium cepa, the common onion or bulb onion. This species is a large, round bulb that may be white, yellow, purple and red. All species within the genus Allium are often considered onions, taxonomically. Among these are garlic, leeks and chives, as well as a number of ornamental plants. All these plants share similarities in leaf shape, flower appearance and bulb formation. Of course, they also share that particular pungent smell and flavor.
The unique flavor of onions and their kin is due to enzymes in the bulb. An uncut onion bulb emits no smell. But when damaged or cut with a kitchen knife, the plant cells release enzymes that combine to form sulfur compounds, source of the strong, distinctive odor. A separate enzyme produces the acidic fumes that bring tears to the eyes of chefs the world over.
Onions probably evolved to have these intense favors and smells to deter ground-dwelling mammals that would otherwise see the bulbs as a tasty lunch. Humans enjoy the pungency, however. Just look at the booming hot pepper industry.
If your home-grown onions don't have enough of that “oniony” flavor for your liking, your plants may be suffering from a sulfur deficiency. Sulfur is so important to the health of many crops that some call it “the fourth macronutrient” (after nitrogen, phosphorus and potassium).
In Napa Valley, it is unlikely that your soil is deficient in sulfur, but the plants may not be absorbing the nutrient. To be accessible to plants, sulfur must be converted into sulfates through the decomposition of organic matter by soil organisms. You can increase the organic matter in your soil by adding manure, compost or mulch. Growing cover crops and tilling them in when they reach the end of their season is also an option. Of course, it is also possible that the onion variety you purchased was a mild one, so always try a few different types.
While growing onions is not difficult, you should note a few things before beginning. Always read the information on the seed package or set package. Some onions need to be consumed quickly after harvest, while others can be stored through winter.
Another difference is between short-day and long-day onions, referring to the amount of daylight hours the plants will receive. Plant short-day onions in fall for harvest the following spring. Plant long-day onions in early spring and harvest in summer. If you are unable to determine which type you have, look at the recommended climate zones. Short-day onions are suitable for warmer climates such as zone 7 and up.
It is pleasing to know that, when growing onions, we are participating in an activity that humans have engaged in for millennia. These connections remind us of our place in history and our responsibility to the future. That said, onions taste pretty good, too.
Fall Faire: U.C. Master Gardeners of Napa County's second annual Fall Faire will take place on Saturday, October 5, from noon to 4 p.m., at 1710 Soscol Avenue in Napa. Tickets are $5 for adults. Children 15 and under are free with an accompanying adult. Purchase tickets online with a credit card. Cash and check only will be accepted at the door. Find more on the Fall Faire at http://napamg.ucanr.edu/fallfaire/.
Next workshop: U.C. Master Gardeners of Napa County will hold a workshop on “Stinking Roses and Edible Alliums: Grow These Essentials for Your Kitchen” on Saturday, October 12, from 9:30 to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. For more details & online Registration go to http://napamg.ucanr.edu or call 707-253-4221.
The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.
- Author: Richard Smith
Onions is a challenging crop in which to achieve good weed control. They are planted in high density configurations that preclude the effective use of cultivation. Cultural practices such as locating plantings in fields have low weed populations, as well as preirrigating up a flush of weeds followed by killing them with shallow cultivation can be effective in minimizing the population of weeds that emerge during the crop cycle.
In general, excellent weed control for many of the common cool and warm season vegetables can be accomplished by a combination of the registered pre- and post-emergence herbicides. The weed control challenges in onions occur with weeds that are not well controlled by currently registered herbicides. It is therefore important to continue to examine any new herbicide options or find new uses for old herbicides to fill in the gaps and address specific weed issues.
In 2018 we evaluated pre- and post-emergent applications of bicyclopyrone (Syngenta Corp), as well as prometryn and linuron applied at the 4-5 leaf stage. The idea for using prometryn and linuron came from a project we were doing on leeks in which both materials were quite safe to this crop. There was low weed pressure in the field, but there was a trend that indicated fewer weeds in all herbicide treatments (Table 1). All treatments had low phytotoxicity ratings. Interestingly, both prometryn and linuron bent the leaves of onions (see photo) in a similar fashion to what we observed in the leek trials; however, there were no other evident phytotoxicity issues. There were no negative impacts of any of the treatments on onion yield. This year we are looking at applications of prometryn and linuron earlier in the crop cycle.