As an avid gardener, I’m always seeking ways to help my plants thrive. This involves understanding how environmental factors like temperature affect their growth and hardiness. When it comes to onions one key question is how cold can onion seedlings tolerate before damage occurs? Knowing their limits guides me in choosing varieties and protecting my crop.
Onions are cool-season vegetables that can withstand some chilly temperatures. But freezing conditions can still harm young seedlings, slowing growth or even killing them off. Let’s explore onion seedlings’ cold tolerance and tips to shield them from harsh weather.
How Cold Temps Impact Onion Seedlings
Mature onion bulbs and plants can brave some seriously frigid conditions. But seedlings and smaller sets are more vulnerable to cold injury. Here’s an overview of how low temperatures affect tender young onion starts:
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Most can tolerate short-term temps as low as 20°F (-7°C) But extended freezing causes cell damage
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Prolonged exposure to 25°F (-4°C) or below can be detrimental and may be fatal
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The roots are particularly sensitive to freezing and may rot after thawing.
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Freeze damage shows first in the foliage, which may wilt, yellow, or collapse.
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Slowed growth and stunted plants are also common signs of cold stress.
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Impaired root function limits water and nutrient uptake, worsening cold injury.
While onion seedlings have some cold resilience, freezing temps that persist can overwhelm their defenses. Taking prompt action to modify their environment is key to avoiding lasting harm.
Tips to Shield Seedlings from the Cold
No gardener wants to see their tender young vegetable crops perish in a spring freeze. Here are some techniques I use to protect my onion seedlings from frigid conditions:
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Cover plants with cloches, cold frames, or fabric row covers to trap warmth. Ventilate on sunny days.
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Mulch heavily around plants with straw, leaves, or other organic matter to insulate the soil.
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Water well before a freeze to keep soil warmer. Moist earth holds more heat.
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In extreme cold, wrap insulation around containers or lift into a sheltered location.
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Avoid over-fertilizing, as succulent growth is more prone to freezing.
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Select cold-hardy varieties like Walla Walla, Red Wing, and Candy hybrids.
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Check for forecasts and be ready to take action before temps drop drastically.
With some simple safeguards, young onion plants can make it through bouts of cold weather. It’s also vital to monitor for signs of damage afterward and allow time to recover.
What to Do After Freeze Events
Even cold-tolerant varieties can experience setbacks when faced with an unexpected hard freeze. Assessing the damage and responding properly gives them the best chance to rebound. Here is my post-freeze game plan for onion seedlings:
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Remove any foliage that is mushy or collapsed to prevent rotting.
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Feel for soft areas on bulbs and trim off damaged outer layers if needed.
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Water thoroughly to restore moisture lost to frozen soils.
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Make sure plants get ample sunlight to restart growth after several overcast days.
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Apply a balanced soluble fertilizer according to package directions to aid recovery.
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Be patient. It may take 1-2 weeks for new leaves to emerge and growth to pick back up.
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Watch for signs of stress like stunted plants or distorted foliage and troubleshoot as needed.
With attentive care and favorable weather, your onions can make a comeback after being hit by a late frost. But sustained freezing temperatures beyond their resilience will require replanting.
Choosing Cold-Hardy Onion Varieties
One way to boost your onions’ odds of withstanding cold snaps is to select adapted, cold-tolerant cultivars. Here are some of my top recommendations:
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Stuttgarter Giant – Very hardy, large yellow storage onion. Tolerates down to -20°F (-29°C) when established.
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Candy – Intermediate-day sweet hybrid with improved frost tolerance. Matures in 110-120 days.
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Patterson – Early-maturing yellow onion bred for cold climates. Ready for harvest in just 100 days.
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Super Star – Extremely cold hardy hybrid yellow onion. Tolerates temps down to 10°F (-12°C).
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Red Wing – Purplish-red onion with good frost resistance. Stores well up to 8 months after curing.
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Walla Walla – Mild, sweet yellow onion that withstands cold as low as 10°F (-12°C).
Seeking out onions bred to thrive in chilly conditions gives your crop an advantage when cool weather strikes. Pair cold-hardy varieties with protective measures, and your seedlings can make it through those last spring frosts.
Optimal Temperatures for Growth
While onion seedlings have some tolerance for cold conditions, they grow best within an ideal temperature range:
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Minimum temp for growth: 40-50°F (4-10°C)
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Optimal temp for growth: 55-75°F (13-24°C)
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Ideal temp for bulb formation: 60-65°F (16-18°C)
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Max temp for growth: 75-85°F (24-29°C)
Providing warmth early in the season accelerates germination and leaf growth. Cooler temps in the 60s F later on produce the largest bulbs. High heat causes bolting. Monitoring soil and air temperature helps predict performance.
Using Low Tunnels, Mulch, and Row Covers
To regulate temps around onion seedlings, I often use season extending techniques like:
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Low tunnels made from hoops and plastic sheeting to trap heat.
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Thick mulch blankets to insulate the soil and protect roots.
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Fabric row covers to shield plants from wind and cold air.
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Cold frames or cloches for targeted protection of vulnerable plants.
These tools create warmer microclimates that boost growth. I ventilate on sunny days to prevent overheating and provide air circulation. With some simple DIY shelters, my seedlings thrive despite fickle spring weather.
Getting a tasty onion harvest starts with helping young plants withstand early season chills. Knowing the cold tolerance threshold for seedlings guides me in safeguarding my crop. Onion seedlings can brave short-term freezing in the 20s F when established. But hard freezes below 25°F for extended periods require action like mulching, row covers, or cloches to avoid lasting harm. With thoughtful protection measures and cold-adapted varieties, your onions can flourish through cool and frosty times on their way to mature bulbs.
A quick guide to onions
- You can start onions from seeds, babies, or small bulbs known as “sets.” “.
- Plant onions early in spring.
- If you want to grow onions, you need soil that drains well and has a lot of
- Onions are shallow-rooted and require constant moisture for proper growth.
- When about half of the onion tops are dry and falling off, it’s time to pick them.
- Curing is essential if you want to store onions. You must dry them in a warm, dry, well-ventilated area.
Long-day and short-day onions
Onions (Allium cepa) have relatives that include garlic, chives, leeks and shallots.
When grown in Minnesota, most storage onions are long-day types that need at least 14 hours of daylight to form bulbs. All onions require full sun for the best growth. Overcast skies and cool temperatures during the growing season will delay bulb formation.
Sweet or mild onions are short-day onions. Although you can grow them in Minnesota, they will generally develop small bulbs. Bunching onions, including scallions and Egyptian walking onions, have green stalks.
- Have your soil tested.
- Onions grow best in well-drained soil with pH between 6. 0 and 7. 0, and high organic matter. Use potassium (K) and phosphorus (P) as directed by the soil test. Many Minnesota soils have enough phosphorus. Use a low- or no-phosphorus fertilizer unless your soil test report says that you need to add more phosphorus.
- Adding well-rotted manure or compost to your soil in the spring or fall will raise its organic matter level. Do not use fresh manure because it could have bacteria that are bad for you and make weed problems worse.
- Onions need a lot of nitrogen, but too much nitrogen can cause them to mature late, have big necks that are hard to cure, soft bulbs, green flesh, and bad storage quality.
- Side dress with fertilizer after root systems are well-developed. Use urea (45-0-0) at a rate of 0 times during the growing season. 25 to 0. 5 pound per 25 feet of row. There should be about six inches of space between the fertilizer and the onions in the row. Scratch it into the soil.
- Do not use “Weed and Feed” type fertilizers on vegetables. They contain weed killers that will kill vegetable plants.
Direct seed as soon as the soil is workable in the spring.
- Sow seeds in a 2-inch wide band
- 1/4 to 1/2 inch deep
- in rows 12 to 18 inches apart.
After seedlings emerge, thin to 3 to 4 inches apart.
Some seed companies sell onion transplants. They can tolerate light frosts, and you can plant them when temperatures reach 50° F.
You can also raise your own transplants by starting seed indoors 10 to 12 weeks before planting outside.
- Sow seeds 3/4 of an inch deep.
- Keep evenly moist.
- Loosen plants when ready to transplant.
- Trim roots to 1/2 inch.
- Trim tops to 4 inches long.
- Plant 2 inches deep, 3 to 4 inches apart, in rows that are 12 to 16 inches apart.
You can also plant onions from sets, which are small bulbs grown the previous year. Most of the sets available in Minnesota are of the short-day type. If using sets, plant them as soon as the soil is workable in the spring.
Are Onions Frost or Freeze Resistant? : Garden Space
FAQ
When can onion seedlings go outside?
What is the minimum temperature for onion seedlings?
How hardy are onion seedlings?
How cold can seedlings survive?
What temperature can onion seedlings tolerate?
Onion seedlings can tolerate temperatures as low as 20°F (-7°C). Onion seedlings can tolerate a cold temperature for several days. Onion seedlings can tolerate light intensity of up to 6,000 foot-candles. Onion seedlings can tolerate various soil types, including sandy, loamy, and clay soils.
How can one consume onions?
In the raw version, we consume a greater amount of potassium, calcium and phosphorus. We can think of creative ways to use onions, such as: salt seasoned with onions, pickled, in salads and as an ingredient in guacamole. Consumption of sautéed onions is common in sauces, as an accompaniment to meats, quiches and other dishes. An interesting way is to use it with rice at the time of cooking, to give a special flavor to the main dish. Fried, it can be part of the main course or an appetizer, like the famous onion rings. However, attention: the use of flour for breading and oil for dipping contribute to the increase of cholesterol.
Can onion seedlings grow in cold weather?
Onion seedlings can tolerate a cold temperature for several days. Onion seedlings can tolerate light intensity of up to 6,000 foot-candles. Onion seedlings can tolerate various soil types, including sandy, loamy, and clay soils. Onion seedlings prefer moist soils, but can tolerate dry soils for short periods of time. 1.
How do you grow cold tolerant onions?
Onions should be planted in an area with full sun and well-drained soil. Cold-tolerant onions can also benefit from being covered with a layer of straw or other organic mulch, as this can help protect them from cold temperatures. Finally, it’s important to keep an eye on the weather when growing cold-tolerant onions.