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Onion Growing Stages (Life Cycle): Ultimate Guide

Onion Growing Stages (Life Cycle): Ultimate Guide

Onion is a vegetable that you can easily and quickly grow in your garden and even in a pot. Let’s know about the onion growing stages and how you can grow healthy and big onions in your home garden. Remember that you will need to water and drain your onions more as they have shallow roots and hollow leaves and stems. Thus, it is best to plant them in organically rich and well-drained soil. 

The onion growing stages are

  • Germination
  • Seedling growth
  • Vegetative growth
  • Formation of bulb
  • Maturation of bulb
  • Harvesting the onions

Germination is when the seed sprouts and the shoot emerges from the seed and out of the soil. Vegetative growth is the rapid growth phase of the plant; when the white bulb is formed and green leaves grow rapidly. The plant discontinues growing any further in the bulb formation stage and all the plant’s energy is focused on growing the bulb bigger. Each of the onion growing stages is important and you need to give the plant a different kind of care. Read the following details about all the stages and the care needs of the plant during each of them.

1. Germination


It is the process by which a seed changes into a plant. It is the first and one of the most important among the onion growing stages. The roots start to develop downwards and the shoot system starts growing upwards out of the soil. Usually, onion seed germination takes from a few days to a few weeks. This time duration may vary depending on the soil, humidity, temperature, and the variety of onions you are growing. 

Germination usually speeds up with higher temperatures and humidity and with low temperatures and humidity, germination is usually slow. Soil is the next factor that affects the time for germination. Clay soils drain slowly and stay saturated; this makes them not a good choice for faster germination

2. Seedling growth

Seedling growth

The first step of the life cycle of an onion plant is onion seedling. The tiny onion seed develops green shoots and grows continuously in this stage. Good drainage, regular watering, and fertilizing are needed for healthy and excellent growth. Good sprout conditions for onion seedlings are a warm temperature and a good moisture level. 

You must provide abundant water and other nutrients to the onion seedlings at this stage as the plant has to reach its best height. It will produce large and healthy bulbs if it grows fast. Conversely, if you don’t provide it with enough nutrients and moisture, the plants will not get tall and you will have smaller bulbs. 

3. Vegetative growth

Vegetative growth

This step in the onion growing stages starts from the appearance of seedlings from the soil and ends when the plants start making the bulbs. The onions need a lot of watering and nutrients at this stage to grow healthy and bigger bulbs, insufficient watering will reduce the growth process. 

You should also make sure that the plants have enough spacing in between as they need a lot of space to grow during the vegetative stage. Onions will stay small and stunted if planted closer. The different onion varieties have different lengths of their vegetative stages, some have completely formed bulbs in some weeks, while some may even need a few months to form the bulbs fully. 

4. Formation of bulb

onion growing stages

Next in the onion growing stages is the plant entering into the bulb formation stage when it produces a small bulb at the top part of its stem, which keeps growing till the harvest season. There are small fresh onions under the soil’s surface, the number and size depend on the onion variety you are growing and the conditions you provide it with. Some may produce smaller and multiple bulbs, but others may have a single big bulb.  

You must keep a note of the harvesting time and harvest the onions on time, if you delay the process, the onions will get rotten. 

5. Maturation of bulb

Maturation of bulb onion growing stages

When all the onion leaves turn brown and pale, this marks the start of the maturation stage of the onion growing stages. This usually happens in a hot and dry time. The plant starts shedding its outer leaves to get less water loss. The bulb stores all the plant’s energy and carbohydrates at the cost of its leaves. You will notice the top sides of the onions turning into straws and the bit of purple dash will totally fall off. This is the time when onion necks are well-shaped and it is the prime duration of onion maturation. The onion necks are soft enough to blend easily without any damage. 

6. Harvesting the onions

Harvesting the onions onion growing stages

When onions reach their harvesting stage, you should harvest the ripe and matured onions before they start deteriorating. Besides, there are many ways to harvest onions. The most common one is to use a digging fork and loosen the soil around the onion. You can then easily pull out the onions using your hands. You should do this carefully to make a perfect harvest without damaging the onions. 

However, You can also use a spade or shovel as another popular way of harvesting onions. Start by chopping off the leaves from the surface, and then finally dig off the onions from under the soil. 

You can choose any method for harvesting onions but do it carefully as you must leave enough stalks for the onions to keep them together. Once you complete the harvest, onions need to be cured for almost 20-25 days. This makes it easier to store the onions and keep them as rigid as you like. 

Growing tips for onions

After knowing about the various onion growing stages, it is important to know some tips to ensure the process is successful for you.

  • Use well-draining and fertile soil and add compost, a small handful of fertilizer, or well-rotted manure to the soil before growing onions. 
  • Keep the soil moist when sowing the onion seeds and cover them lightly after sowing them shallowly. It is better to sow a number of seeds greater than how much you need as there are usually seed losses during poor germination.
  • Mulch the seedling bed to reduce weeds and transplant the seedlings from places where there has been a lot of germination to where there are sparse seedlings.
  • The best advice for sowing seeds is to sow them at the right time according to your climate. Sow towards the end of autumn if you live in places with subtropical climates. While in warmer climates, sow the seeds through the driest part of the year. It is best to sow seeds through spring in cold climates.
  • Check the number of daylight hours and your climate before choosing the right variety of onions to grow. You should also consider when you are growing and how early you need the harvest while looking at onion growing stages. For instance, for winter planting, you should plant varieties that mature fast and early. 
  • Maximize your space by growing the onions in the garden bed. This makes the onions grow taller rather than wider and prevents weeds from growing around the plant.

Common onion problems

It can be challenging to grow root vegetables as you cannot see what is bothering your bulbs under the ground. But if you care for onions properly and provide them with the right growing conditions, you will be able to minimize the risk of failure and crop damage. We list some common issues that arise when growing onions and also include tips to fix them.

  • Stunted growth: If you see that your seedlings and onion plants are growing at a snail’s pace, then it can be a result of lack of nutrients or poor soil conditions. The soil should be loose, well-draining, and has a pH of between 6.0 and 6.8. To provide essential nutrients to the plants, apply a balanced fertilizer.

Also There are

Stunted growth onion growing stages
  • Leaves turning yellow: Nutrient deficiency, pests, and lack of water can make onion leaves turn yellow. Feed the onion plants with a fertilizer containing phosphorus, potassium, and nitrogen, and water the plants regularly. Look out for thrips and maggots that can damage the leaves significantly.
  • Wilting plants: Both overwatering and underwatering can make the onion plants wilt and droop. Check the soil moisture level and the surrounding environmental conditions to determine how much watering your onion plants need.
  • Deformed bulbs: Compact soil and inconsistent soil moisture levels can prevent the bulbs from forming properly. Loosen the soil to make space for bulbs and water the onion plants regularly.
Deformed bulbs onion growing stages
  • Diseases and pest infestation: Onion crops can be damaged significantly by onion maggots, thrips, and fungal diseases including white rot and downy mildew. Remove the infected plants immediately, maintain good plant hygiene, and practice good crop rotation, to prevent these issues. You may also use natural or chemical pesticides to solve these problems. 

Are you also planning to grow chillis after knowing the onion growing stages? Then read Chilli Plant Growing Stages (Life Cycle): Ultimate Guide


Onion is part of many different cuisines around the world and it also promotes weight loss. It contains lots of fiber and makes digestion better, plus you can store onions for many months. If you know about the onion growing stages, then you can grow them from seed at home easily. He onion plants need temperatures between 60 and 80 degrees Fahrenheit with 6 to 7 hours of daily sunlight. You can start following the steps we mentioned above and the growing tips to get an amazing onion-growing experience and harvest onions in your own homes and gardens. 

How long is the onion life cycle?

Similar to many other root vegetables, the life cycle of onions is two years. The two year life cycle makes the plant use all its energy to grow green fleshy leaves and store energy for the next year. This energy reserve is the onion bulb that we eat. The bulb is usually at its biggest point at the end of the first year, so this is the time to harvest onions. 

If you allow the onion to grow naturally, it sprouts in the next spring and grows a flower. The bulb is reduced in size and shriveled as the plant uses its stored energy to grow the flower. The bolting and going to the seed stage of onions make the bulb useless. So, only let this happen if you are growing onions for seeds. 

When to harvest and grow the different types of onions?

When to harvest and grow the different types of onions?

To fully understand the onion growing stages, it is important to know about the planting, harvesting, and growing timelines for different onion species. This will help you to choose the variety you wish to grow at home:

Onion varietyWhen to plant?HarvestGrowth type
Green (Scallions)Early springEarly, when they are immatureGrows in bunches
White onionsEarly springFallGrows alone
Yellow onionsEarly springFallGrows alone
Purple onionsEarly springFallGrows alone
Spring onionEarly springEnd of spring or early summerGrows alone or in bunches