The Ultimate Onion Timeline: How Long Does It *Really* Take For Onions To Grow? (The 90-120 Day Secret)

The question of "how long does it take for onions to grow" is one of the most common and complex in vegetable gardening, and the simple answer is often misleading. As of the latest horticultural updates in December 2025, the total time from planting to a fully cured, ready-to-store onion bulb is typically between 120 and 150 days. While the bulbing process itself takes 90 to 120 days from a transplant or set, the crucial step of curing adds an extra 2 to 4 weeks, which is vital for long-term storage and often overlooked in quick guides. Understanding this timeline requires moving beyond a single number and looking at the three major variables: your starting material (seed, set, or transplant), the specific variety (day-length type), and the essential post-harvest curing process. We will break down each phase to give you the most accurate and up-to-date schedule for your harvest.

The Definitive Onion Growing Timeline: Seed, Set, or Transplant?

The duration of your onion crop’s life cycle is heavily determined by how you begin. Gardeners typically choose between three starting materials, each offering a different speed and level of effort.

1. Growing Onions from Seeds (The Longest Route)

Starting onions from seed is the most economical method, but it demands the longest commitment. The total process is split into two phases:

• Indoor Start Time: Seeds must be started indoors approximately 8 to 10 weeks before the last expected frost date. This early start is critical because the Allium cepa plant needs a long vegetative phase to develop enough green tops (leaves) before the bulbing process begins.
• Outdoor Maturity Time: Once transplanted into the garden, the seedlings will take an additional 90 to 120 days to mature into a full bulb.
• Total Time: Expect a full cycle of 5 to 7 months (150 to 210 days) from the day you sow the seed until harvest.

2. Growing Onions from Transplants (The Standard Route)

Transplants are young onion seedlings that have already completed the indoor starting phase. This method is the most popular for home gardeners as it shaves off the initial two months of indoor work.

• Maturity Time: Once planted in the garden, transplants will require 90 to 120 days (3 to 4 months) to reach full bulb size.
• Advantage: Transplants offer the best balance of speed, bulb size potential, and variety selection.

3. Growing Onions from Sets (The Fastest Route)

Onion sets are small, immature bulbs that were grown the previous year and then dried out. They are the quickest way to get a harvest, though they sometimes result in smaller final bulbs and have a tendency to bolt (go to seed) if stressed.

• The Untouchable Privacy 7 Secrets Of Rachel Mcadams And Jamie Lindens Life Beyond The Red Carpet E820e

• Maturity Time: Sets are already a year into their life cycle, so they typically mature the fastest, requiring only 60 to 75 days (2 to 2.5 months) after planting in the early spring.
• Best For: Gardeners who want a quick crop or are primarily interested in harvesting green onions (scallions), which can be pulled much earlier.

The 3 Critical Factors That Control Your Onion's Maturity Date

The single most important factor controlling the growth time of your onion is its "day-length" requirement. Onions are photoperiodic, meaning the amount of daylight hours they receive triggers the switch from leaf growth (vegetative phase) to bulb formation (bulbing phase).

1. Short-Day Onions

These varieties are ideal for the Southern regions of the United States (Zones 7 and warmer). They require the fewest hours of daylight to begin bulbing.

• Daylight Requirement: 10 to 12 hours of daylight.
• Maturity Time: Generally on the shorter end of the scale, often around 90 to 100 days from transplant.
• Examples: Yellow Granex, Red Creole, Texas Sweet.

2. Intermediate-Day Onions (Day-Neutral)

Perfect for the mid-latitudes (Zones 5-6), these are the most versatile onions and are often called "day-neutral."

• Daylight Requirement: 12 to 14 hours of daylight.
• Maturity Time: Typically fall into the 100 to 110-day range from transplant.
• Examples: Candy, Red Candy Apple, Yellow Sweet Spanish.

3. Long-Day Onions

These are the storage onions preferred by Northern gardeners (Zones 6 and colder) where summer days are much longer. They need the most sunlight to form a bulb.

• The Enduring Legacy Of Haylor 5 Shocking Facts About Harry Styles And Taylor Swifts Relationship 10 Years Later Sf662

• Daylight Requirement: 14 to 16 hours of daylight.
• Maturity Time: These often take the longest, maturing in 110 to 120 days from transplant.
• Examples: Copra, Ebenezer, Red Weathersfield, Stuttgarter.

From Seed to Storage: A Detailed 4-Stage Onion Growth Cycle

To master the onion timeline, you must understand the four distinct phases of its growth. Missing a critical window in any of these stages can significantly delay your harvest or reduce the final bulb size.

Stage 1: The Vegetative Phase (First 60-90 Days)

This is the initial period focused entirely on developing the leaves. The number of leaves an onion grows directly correlates to the number of rings in the final bulb, meaning more leaves equal a bigger onion. During this phase, the plant needs consistent moisture and high nitrogen fertilizer (N). Use a balanced organic fertilizer like Nature Safe 7-7-7 or a nitrogen-rich option like blood meal or ammonium sulfate every 3-4 weeks.

Stage 2: The Bulbing Phase (Triggered by Day-Length)

Once the required number of daylight hours is reached (depending on your variety), the plant switches from leaf production to bulb enlargement. The base of the plant will begin to swell and push out of the soil. This is the period when you must ensure the soil is loose and well-drained. Crucially, stop fertilizing with high-nitrogen formulas once bulbing begins, as too much nitrogen at this stage can delay maturity and lead to soft, poor-storing bulbs.

Stage 3: Maturation and Harvest (The Final Weeks)

Maturation is signaled by the "neck fall-over." The green tops will soften and fall over, and the leaves will begin to turn yellow or brown. This is the plant's way of signaling it is finished growing and is diverting all remaining energy into the bulb. Once 50% to 75% of the tops have fallen over, the onions are ready for harvest. Gently loosen the soil around the bulbs and pull them out of the ground.

• The Facts Of Life Cast Where Are Eastlands Girls Now 2024 Updates 2tx8p

Stage 4: Curing (The Essential 2 to 4 Week Finish)

This is the most critical step for long-term storage and is often the difference between an onion that lasts a few weeks and one that lasts all winter. Curing is the process of drying the outer skin and neck.

• Duration: 2 to 4 weeks for pungent (storage) varieties like Copra or Red Weathersfield.
• Method: Lay the harvested onions in a single layer in a warm, dry, and well-ventilated location, such as a covered porch, shed, or greenhouse. Do not wash them. Once the necks are completely dry and the outer skin is papery, they are fully cured and ready for storage.