How to grow big onions

When most people see big onions, they can never imagine growing them like that in a thousand years. This is because onion plants often fail to produce the large firm bulbs and are susceptible to a host of diseases. However, following a few simple tips can make a big difference in your harvest.

It all starts with whether you should start your crop with seeds, sets, or transplants as well as the varieties you should grow. Make sure you have the right onion. You need short day cultivars which include Hanna, San, Shahar, Red Creole and Texas Grano take between 220 and 230 days to mature.

1. Start early

Onions need all the time you can give them. An early start is always beneficial, because the longer onion plants grow before they form bulbs, the bigger and better the onions will be.

2: Nitrogen

Most people think that because onions rare root vegetables, they require lots of phosphorus. However, each leaf the onion puts out is a ring on an onion, this means the more leaves, the bigger the onion. You want growth especially in the early stages so, nitrogen is the way to go.

Related article: Onions-Low maintenance crops for beginner farmers

3. Avoid onion sets, start from seed

Onion sets are perfect for lazy farmers. They are already started and easy to plant. But, they might not give you the best results. The biggest problem with onion sets is that many onion growers will grow small onions, store them, and sell them as onion sets. Furthermore, onions are bi-annual – they flower on the 2nd year of growing. Therefore, when you grow them, they will flower that year. This unfortunately will not only reduce the storage time, but it will also reduce the amount of energy to enlarge the ball.

4. Water frequently

Onions love water, because the more water, the more plump the onion can get. As much as you shouldn’t overwater, the soil should also never be allowed to get bone dry.

5. Mulch

Mulching helps to eliminate weeds which steal nutrients and water from the onion. The weeds can also transmit viruses and diseases to the onion.

6. Ensure you have good soil

Sandy loam soil is the ticket for large onions. When the onion is compacted in the soil, it leads to a pinched onion which reduce the size of the onion. However, a bulb that can freely expand in the soil is usually the biggest.

7. Don’t harvest too quickly

Leave the onion plant till the tops become like paper. Sometimes, the tops die back, but the onions still continue to absorb water for up to 2 weeks. So, leave an onion in the ground till the tops fall over and become like paper.

Related article: Basics on growing garlic

53 thoughts on “How to grow big onions

  1. Is there a farm that I can go to, to practically learn onion farming. I am very much interested in growing onions as my main crop.

    1. Hi Esther, please join groups on Facebook. There you can find a farmer near you that would be able to show you what they’ve done.

    1. Hi Peter, It’s not possible to estimate how much profit you can make. There are a number of factors to consider including whether the land is leased or not, farm worker salaries etc. However, if all growing conditions are met, you can get about 30 large bags of sweet potatoes from an acre land.

  2. Which Part Of Of Zambian Is Suitable To Grow Onion 2 Hector.Apart From Seedling,do Onion Need Fertilizer? If So What Type Of Fertilizer And The Quantity For 2kg Seedling.Where Do I Buy The Fertilizer.What Is The Best Time To Start Onion Farming?

    1. Please go to the search bar on our website and type onion.We have a few articles on onions. All your questions will be answered. Thanks

    2. How are you Sir.

      Am specialized in rain fed onion and we use sets, 1kg will give u one Lima, with the 2kg u r talking about ,that’s two limas,

      But for a starter like u sound ,I would advise you to start with a Lima just one kg, if well managed it can give u up to K200,000.

      All you need is management, spray copper oxy, cyphermethrine every week, prevention is better than cure.

      7days from planting your sets, apply D compound fertilizer, and at 4 to 6 weeks apply CAN fertilizer, this will improve the quality of your onions.

      Remember Copper Oxy is on the preventive side, but once u begin to see fungals ,change to something on the curerable side.

      I thank u

      1. Hi Mad Farmer Kapwata,
        How much in terms of KGS of onion sets do I need to plant on a Lima? Also how many bags of fertilizer of each type will be required on the same space of land?

    1. Good day Kenneth,
      You have to dry the onions before you store them in a place that is well ventilated, cool and dry. You shouldn’t store them in a plastic bag because they need to breathe. Inspect all onions for soft spots, mold or other signs of damage and only perfect onions as they are suitable for long-term storage. If they are already sprouting, don’t think of storing them – use them immediately. If you’re storing few onions, cut the roots and place the onions in a pantyhose(onion sacks) and tie in knots after each onion and hang the pantyhose in a cool, dry place.Onions in a pantyhose For larger quantities, once the necks are completely tight and dry, and the stems contain no moisture, trim the roots off the bottom of each bulb. The leaves can also be trimmed to within 3 cm of the bulb and hang in mesh bags

    1. Onion root maggots eat onion roots and bulbs.Especially when the Zambian rainy season is in full swing. Onions are harvested after 25-35 weeks. So, ensure that by then there’s no rain so your onions can dry for harvest.

    2. It will be great if you specify how many bags of fertilizer i can use in a lima of onion and what type of fertilizer in 50 kg bags.

  3. Hy.thanks for THIS platform..i planted some onions in may and got very big onions by september and women traders came to buy the onions from my farm!(imagine my excitement as a new farmer!!!)..i’m now “hooked” and want to plant more through the rainy season because i noticed that in april ,onion prices were at MAX in most parts of zambia…which variety can i grow in rainy season and/or what agri-chemicals can i use to support my onions?..Please: help me grow!

    1. Tell me dear Nakwambwa what measure were you using when selling and price, mine are almost ready I need info pls.. Thanks

  4. Thank you so much for such a wonderfull and educating page!To my fellow farmers,”Never stop learning because life never stop teaching”.

  5. The article is very inspiring and I am very interested in onion farming and other crops.Please continue publishing these information that will change our country….

  6. Hai my name is Paul and am aspiring to plant onions during the this rain season . what variety and most importantly is it possible to do so

    1. Hi Paul, We have a number of articles for onions. Please use the search function on our site and type onion.

  7. I want to disagree with you that planti g onion sets is for lazy farmers Well, according to my experience onion sets does very well during rain season.The sets are disease and drought resistant.They mature first and grow very big bulbs.

    1. Hi Sam, Maybe the reason we have small onions is because of staying in comfort zones! If we as farmers tried other methods, maybe we would improve our quality of onions.

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