Onions are a staple in cuisines around the world Their versatility, flavor, and health benefits make them an invaluable addition to any kitchen If you want to enjoy fresh onions from your own garden, knowing their growth timeline helps ensure you plant and harvest at the right time. So how long does it take for onions to mature?
Overview of Onion Maturation
On the whole, it takes 3-4 months for onions to reach maturity and be ready for harvesting. However, many factors influence the exact duration, including:
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Onion variety – Early maturing varieties can be ready in 60-100 days while long-day onions take 100-120 days
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Time of planting – Onions planted earlier in spring mature faster than those planted mid to late spring.
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Climate and geographical location – Cooler climates delay maturation compared to warmer climates.
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Growing conditions – Ideal conditions like loose, fertile soil and sufficient water shorten the maturation period.
While 3-4 months is the average, understanding how onions grow through different phases helps determine maturity more precisely.
The 13 Stages of Onion Growth
Onions are biennial, completing their lifecycle over two years. In year one they form bulbs, while in year two they produce seeds. We’ll focus on the first year of growth comprising 13 key stages:
1. Planting
This involves sowing seeds or planting onion sets (small bulbs). Onion seeds take longer to form bulbs but allow earlier planting. Sets form bulbs quicker but have shorter shelf life.
2. Germination
Seeds sprout tiny roots and shoots within 7-10 days if planting depth, temperature and moisture are ideal.
3. Vegetative Growth
The onion forms leaves and a root system. This stage lasts around 60 days.
4. Bulb Development
The bulb begins to swell as the plant continues growing leaves. Bulb and leaves grow together over 60 days.
5. Harvesting Leaves
Once the bulb has started swelling, leaves can be snipped off for use.
6. Maturation
The bulb expands and texture changes as sugars concentrate. signals maturity.
7. Harvesting Bulb
When foliage yellows and falls over, the bulb can be harvested.
8. Vegetative Senescence
If left in ground, leaves yellow and wither as the plant prepares for winter.
9. Year 2 Vegetative Growth
In spring, new leaves emerge. Bulbs may split into multiple smaller bulbs.
10. Flowering
A tall, central flowering stem emerges, ending leaf growth.
11. Pollination
Flowers are pollinated by insects and wind.
12. Seed Formation
Pollinated flowers form seeds over several weeks.
13. Plant Senescence
After seeds mature, the plant dies back entirely.
Determining Onion Maturity
When can you conclude your onions have reached maturity? Here are the tell-tale signs bulbs are ready for harvesting:
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Appearance of foliage – The green tops turn yellow and fall over.
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Bulb firmness – Mature bulbs feel solid when gently squeezed, not spongy.
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Neck softness – The neck area where leaves emerge goes soft.
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Size – Bulbs reach a good size for the variety. Don’t expect huge bulbs from scallions!
Monitor your onion patch to spot these indicators of maturity. Once you see several signs, it’s time for harvest.
Onion Varieties and Maturation Times
Not all onions are created equal when it comes to maturation rate. The variety you select influences the timeline.
Early maturing – 60-100 days
- White Lisbon
- Red Baron
- Candy (hybrid)
- Patterson (hybrid)
Midseason maturing – 100-120 days
- Copra
- Red Wethersfield
- Yellow Granex
- Vidalia (sweet)
Long day – 110-150 days
- Ailsa Craig
- Walla Walla
- Southport Red Globe
- Evergreen Hardy White
Specialty – Varies
- Cipollini – 90-110 days
- Pearl/Boiling – 60-90 days
- Scallions – 50-60 days
Consider your climate and desired harvest period when choosing varieties.
Factors Influencing Maturation Time
Many variables affect the maturation rate of onions. Here are some key factors:
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Day length – Onions require long daylight exposure. Long-day varieties need 14+ hours while short-day types need 12 or less.
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Temperatures – Onions thrive in cool conditions. Consistent warmth above 80°F slows development.
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Planting time – Earlier planting allows more time to mature before summer heat hits.
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Soil – Loose, fertile soil encourages better bulb swelling than compacted or nutrient-poor soil.
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Watering – Adequate moisture prevents stress and keeps plants growing steadily.
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Pests/diseases – Attacks from insects, fungi or bacteria slows maturation and reduces yields.
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Weather – Environmental stresses like frost, flooding or drought lengthen time to maturity.
Tips For Quick Maturation
You can positively influence how quickly your onions reach maturity. Here are some useful tips:
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Select early-maturing varieties suited to your climate.
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Prepare planting beds with loose, nutrient-rich soil.
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Plant onion sets or start seeds indoors for transplanting outside later.
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Use row covers at planting to boost temperature and deter pests.
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Water thoroughly when top 2 inches of soil become dry.
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Side-dress growing onions with balanced fertilizer.
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Control weeds to prevent competition for nutrients.
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Monitor for pests and diseases, treating issues promptly.
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Harvest bulbs promptly once mature to avoid rotting.
Storing Mature Onions
Once your onions have reached full maturity, they need to be harvested and stored properly. Here’s how:
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Loosen soil with a fork and lift bulbs gently. Don’t pull tops.
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Allow to dry out of direct sun for 2-3 days.
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Trim tops to around 1 inch, leaving roots intact.
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Cure bulbs by spreading out in a single layer in a warm, dry spot for 10-14 days.
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Store cured bulbs in mesh bags or food-grade boxes in a cool (32-40°F), dry location.
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Check regularly and remove any bulbs showing signs of rot.
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Properly stored, most onion varieties will last 2-4 months.
Enjoying the Fruits of Your Labor
Part of the joy of gardening is finally getting to harvest and eat the veggies you lovingly tended for months. With onions, that delicious payoff comes around 3-4 months after planting.
Now that you know the full trajectory of onion growth, you can better time your planting. Follow the maturity cues to recognize the perfect moment for gathering your homegrown bulbs. Then cure and store them properly to enjoy fresh onion flavor for months to come.
How to Plant Onions Indoors
Whether you’re planting seeds or sets, get a shallow tray and fill it with compost to the top. Modular trays with a small section for each bulb are ideal.
- Plant seeds 1/4 to 1/2 inch deep, or plant the onion bulbs so that the pointy end is just peeking over the top of the soil.
- Lightly water the tray and let it drain through.
- Set onions in a warm place, such as a well-lit windowsill.
- Thin to 3 to 4 inches.
Growing Onions in Containers
You can also grow onions in containers! Prepare a container that is at least 10 inches deep and as wide as possible (to allow for space between maturing onions). A 5-gallon bucket will support 4 to 6 onions, and a tub many more. Place the container where it will receive the maximum hours of direct sunlight per day. (It will be heavy to move once filled and planted.)
Provide a well-draining potting mix that is rich in organic matter; add compost or well-rotted manure. Mix in a complete fertilizer, per the package guidance on container size, or fertilize with diluted fish emulsion or compost tea. Varieties
Onion varieties are categorized based on whether they’re “long-day”, “short-day”, or “day-neutral” varieties. This is because they are “photoperiodic,” meaning that hey grow in response to day length—the number of daylight hours needed to trigger bulb formation.
Short-day onions grow best in the southern United States, between 25° and 35° north latitude, and start bulbs when day length reaches 10 to 12 hours. The earlier that short-day onions are planted, the larger they get. In the South, onions can be planted in the fall and overwintered. Since they continue to grow throughout the winter, they will be ready for harvest in the spring.
Intermediate, or day-neutral, onions are best suited to the middle tier of U.S. states, approximately between latitudes 32° and 42°, and start bulbs when day length reaches 12 to 14 hours.
Long-day onions grow best in the northern states, between latitudes 37° and 47°, and start bulbs when day length reaches 14 to 16 hours.
Do not try to fool Mother Nature: Short-day onions planted in a long-day zone will result in small bulbs—not an early harvest.
Long-day varieties:
- ‘Yellow Sweet Spanish’: large, round shape; yellow-white.
- ‘First Edition’: high-yielding, stores well, flavorful, creamy-yellow
- ‘Red Wethersfield’: flat bulbs that store well, white flesh, red-skinned
- ‘Aisa Craig’, ‘Walla Walla’: huge bulbs
- ‘Buffalo’, ‘Norstar’: produce early but keep only until late December
- ‘Copra’, ‘Southport Red Globe’, ‘Sweet Sandwich’, ‘Yellow Globe’: keep well
- ‘Red Florence’: heirloom; 4- to 6-inch long, dark purple-red, torpedo shape; mild, sweet
- ‘Ailsa Craig’: heirloom; named for a Scottish island; large, up to 8 inches in diameter; average 2 pounds; pale yellow skin, globe shape; mild, sweet
- ‘Gold Coin’: cipollini; 1-1/2- to 3-inch yellow flattened bulb; pungent flavor sweetens when cooked
Short-day varieties:
- ‘Stuttgarter’: sold in sets, early maturity with a slightly flat shape, yellow
- ‘White Bermuda’: extremely mild, with thick, flat bulbs; white
- ‘Red Burgundy’: good table onion with mild, sweet white inside; short-term keeper
- ‘Crystal Wax White Bermuda’: a great onion for pickling when harvested at pearl size
- ‘Hybrid Yellow Granex’: sweet, Vidalia type
- ‘Red Creole’: heirloom; 3- to 4-inch, dark red globe shape; pungent
- ‘Southern Belle’: ruby color throughout
- ‘Texas 1015-Y Supersweet’: stores well
- ‘Yellow Granex’: Vidalia type; 3- to 4-inch, yellow, flattened globe shape; crisp; said to be the sweetest of the super sweet
Day-neutral or intermediate varieties:
- ‘Candy’: golden, thick-flesh, jumbo bulbs; stores well
- ‘Red Stockton’: large, red-ringed, white-flesh bulbs
- ‘Super Star’: large, sweet, white bulbs
- ‘Purplette’: mini onion, at 1-1/2 inches; glossy, burgundy red when raw; pastel pink when cooked or pickled; mild, sweet
- ‘Southport Yellow Globe’: early; 2-1/2- to 3-1/2-inch thick-skin yellow globe; mild, sweet
Pull any onions that send up flower stalks. This means that the bulbs have stopped growing. These onions will not store well but can be used in recipes within a few days.
- Spring-planted onions tend to be ready for harvesting by mid-summer.
- When onions start to mature, the tops (foliage) become yellow and begin to fall over. At that point, bend the tops down or even stomp on the foliage to speed up the final ripening process.
- Loosen the soil around the bulbs to encourage drying.
- Harvest by late summer in dry weather. (Wet-harvested onions do not cure well and might rot in storage.)
- When the tops are brown, pull the onions. Handle them carefully, as the slightest bruise (now and in storage) will encourage rot.
- Cut the roots and trim the tops back to 1 or 2 inches (but leave the tops on if you are planning to braid the onions together).
The 2 Most Important Tips for Growing Big Onions
FAQ
How long does it take for onions to fully mature?
Looking down, this is one of the growing onions. Onions require 90 to 100 days to mature from seed, which is around four months.Sep 2, 2023
What month do you plant onions?
2. Plant the onions in late March or early April. For best growing conditions, plant your onions as soon as you can work the ground. Typically, this happens in the springtime right after the last frost. 3. Pick a spot in your garden with full sun. Onions grow best in direct sunlight for most of the day.
What is the average growth time for onions?
Depending on your variety, onion sets can be planted in the autumn or the spring, but they’re usually harvested around the same time – in that late summer to early autumn period around July to September. For spring planters, you’re looking at a growing time of around four to six months.