3 Signs It’s Time to Harvest Your Onions
Every great comfort meal begins with sautéed onions, so knowing how to grow and care for them is essential. But what about knowing when to harvest them? Organic farmer Jenna Rich shares three crucial signs to know it’s time to harvest your onions.
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With proper soil conditions, spacing, and water, onions are a “set it and forget it” type of crop. Whether you’re growing them in raised beds, containers, or ground soil, they prefer loose, fertile, well-draining soil high in organic matter in an area that receives full sun.
The world of onions is one you can get lost in easily. There are many intense and subtle flavors to choose from, including whites, reds, and yellows, and you could grow a new variety every year to find your favorites. For a uniquely sweet red onion, try ‘Red Amposta’ or the consistently large, sweet, juicy heirloom ‘Walla Walla.’
I prefer to grow a mix of onion types, some of which are best for fresh eating and others that will last through the winter for all my soup, casserole, and pasta dishes. Let’s discuss the three tell-tale signs that it’s time to harvest your onions.
Days to Maturity
Most onion varieties take between 90 and 130 days to mature from seed and are ready to harvest sooner when started from sets. Record the days to maturity from the seed packet and plan accordingly. Growers in most regions can sow onion seeds indoors around March or April to be ready for transplanting when the spring weather breaks and the soils warm slightly.
Southern growers can start them as early as January with some heat and humidity control to help germinate and avoid damping off. Fans will help bulk up the onion necks in preparation for true hardening off and transplanting.
Stages of Onion Growth
The three stages of onion maturation include:
Vegetative Stage
Like garlic, the plant focuses its energy on above-ground growth during this stage. You want your onions’ leaves to be large, as this is a good indication of the size the bulb will become. Consistent and deep watering is crucial during this stage. If you don’t provide ample water, premature bulbing may lead to small onions and yields.
Did you know?: Each leaf directly correlates to a layer of onion skin growing around the onion beneath the soil surface.
In general, the following types will be successful in varying zones:
- Zones 7+: short-day varieties
- Zones 5 and 6: day-neutral varieties
- Zones 1 to 5: long-day varieties
Short-day varieties begin when sunlight reaches 11 to 12 hours, intermediate or day-neutral varieties at 13 to 14 hours, and long-day between 15 and 16 hours. Selecting the proper day length for your growing zone is crucial.
Improper selection will likely result in lots of foliage but little to no bulbs. Growers in the mid-section of the United States may have success with either short or long-day varieties, depending on their location.
If you’re unsure, experiment with day-neutral varieties. Why is this important? The length of the day signifies to the onion plant that it’s time to start converting carbohydrates found in the leaves into bulbing energy. The day-length type you selected will determine when bulbing begins.
Bulbing Stage
During this stage, the plant stops putting energy into growing foliage. You’ll notice the soil surface cracking and moving around at the base of the necks as energy shifts to below-ground growth and forming bulbs.
Bolting Stage
You want to harvest your onions before this stage, as the bulb won’t continue to grow once it sends up a flower and goes to seed. Pro tip: If you’re growing an open-pollinated variety and it’s a safe distance away from others, you can leave it be to collect and save the seeds once they’re ready.
While bolted onions are still edible, some of their storability is lost, so use these fresh before the cured ones. To prevent this from happening prematurity, avoid stressful conditions by keeping them watered, especially during drought conditions, protecting them during extreme temperature fluctuations, and spacing them properly at transplant.
Studies show that growers in northern regions can successfully overwinter onions planted in November or December protected inside low tunnels or greenhouses or with heavy straw mulch, with harvest occurring in May or June. Select cold-hardy varieties like ‘Bridger’ or ‘Talon’ for the best results. Remember, the days to maturity may extend what the seed package says when you overwinter because they go dormant in the winter.
Softened Neck
The neck softens when the bulbing onion no longer needs to receive nutrients from the foliage, indicating that it’s almost time for harvest. In preparation for curing and storage, it’s nature’s way to form a cut-off area from the neck to the bulb, preventing moisture or disease from reaching the bulb. The foliage will begin to brown and crisp.
Pro tip: You can harvest onions before their necks are soft for immediate use. You’ll notice the neck is juicy when cut into, as nutrients and moisture flow from top to bottom. These onions will not store well; you should use them within a week of harvest.
Fallen Over Tops
You will know it’s time to harvest onions if the leaves turn brown and flop. New gardeners may get a little nervous when their onion foliage turns brown, crisp up, and falls over, but don’t worry, it’s normal! “Tops down” is a part of onion maturation and shouldn’t cause worry.
When the plant no longer needs to pull energy (carbohydrates) from the foliage, the leaves die back, signifying to growers that it’s nearing time for harvest. Growers should wait for nearly 90% of the tops to fall over before harvesting.
You should have a clear view of the onion bulb now. Once the tops have fallen back, there may still be time between this stage and harvest. Keep your eye on the wrapper, as this accurately indicates proper storability. Give the plant more time if there is green on the wrapper. Each onion should have about 13 layers for the best storage.
Pre and Post-Harvest Care
Storage onions will appreciate one last light watering after all the leaves have dried and the tops have fallen over. Doing so allows them to respire moisture; watering sweeter varieties a bit heavier will enhance their flavor. Cease all watering for one to two weeks before harvest to allow the drying process to begin.
Plan to harvest onions in the morning to allow them to dry in the sun for the day or the two or three following. Gently coax them out with a digging fork to avoid damaging them, shaking off excess soil. Yanking them out may cause bruising, negatively affecting their storability. You may cover them with straw or a shade cloth while they dry in the sun to prevent sunscald.
Once harvested, properly curing and storing onions are vital steps in their long-term shelf-life, so don’t skip them! Proper airflow and circulation during curing helps to remove all remaining moisture and seals the bulb. The foliage that remains should be entirely brown and very crunchy.
Using clean, sharp shears, remove the foliage and roots before storage. Leave the outer skins on to protect them during transport and storage, peeling them back just before use. If you are growing the onions to sell, you may remove the outer layer to make them more appealing and marketable. In general, yellow onions tend to store best.
With proper successive planting and selecting the best varieties for your growing zone, you should have no gaps in onions to use all year!
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