Tips for Growing Bigger Onions

2 comments by Halley -Author at MIGardener

How To Grow Bigger Onions

Often times people look at onions in the store and think, "these are HUGE But I can never grow them like this in a million years." I was one of those people, and often times we try so hard, but only to find out we have golfballs instead of softballs when it comes to onions. I learned from my mistakes, and I will now bring to you the things I learned so that you can too have a truly huge onion for harvest.

Rule 1: Make sure you have the right onion for your growing zone. Onions bulb up based on day length. So if you are SOUTH of the 37* latitude line, you need to go with short day onions. If you are NORTH of the 37* latitude line, go with a long day onion.                                       

Tip 1: Start early. Onions need all the time you can give them, at 100-110 days till maturity, an onion will require all the time you can give it. I typically start my onions indoors about 6 weeks before my last frost date.

big huge onionTip 2: Nitrogen. Many people think that onions require lots of phosphorus because they are a root vegetable, however you want growth. Each leaf the onion puts out is a ring on an onion, this means the more leaves, the bigger the onion. I like to go with blood meal as my organic nitrogen source.

Tip 3: avoid onion sets, start from seed. Onion sets are great if you are a lazy gardener, but just because they are already started and easy, does not mean they will give you the best results. The issue with onion sets is that onions are bi-annual, this means that they flower on the 2nd year of growing. Many onion growers will grow small onions, store them, and sell them as onion sets. This means that when you grow them, they will flower that year and this will not only reduce the storage time that the onions will have, but it will also reduce the amount of energy to enlarge the ball.

Tip 4: Water frequently. Onions like lots of water, because the more water, the more plump the onion can get. The soil should never be allowed to get bone dry.

Tip 5: mulch. Mulching will eliminate weeds. Weeds not only steal nutrients and water from the onion, but it will transmit viruses and diseases to the onion.

Tip 6: Good soil Sandy loam soil is the ticket for large onions. Compaction in the soil will lead to a pinched onion, and this will reduce the size of the onion. A bulb that will freely expand in the soil will be the biggest.

Tip 7: leave plant till the tops become like paper. Even once the tops die back, the onion will continue to absorb water for up to 2 weeks. So an onion should be left in the ground till the tops fall over and become like paper.


  • Ron

    I understand you are to dry out the onion after harvest. How do I go about this? And for how long?

  • Vickey Des Lauriers

    How do I prevent sow bugs from eating the root of the onion? Which caused them to rot. I did know this had happened until I pulled the onions out at the end of the season.
    Thank you

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