Why won't my garden onions grow larger?

Becky P
by Becky P

I consider myself having a green thumb, but the one thing I can't do is grow onions as large as the ones in the store. I use yellow or white onion sets, found at the local store, because I love to eat green onions, and they grow fast. However, when I stop harvesting the green onions, my other onions will not grow any larger than an oversized golf ball. What gives? My mom always said not to let the July rains get them, but I have left them in the ground until Sept. sometimes, and still no large onions.

why won t my garden onions grow larger, gardening
  11 answers
  • I could be totally wrong, but all vegetables are demanding of nutrients and water. Poor soil lacking in organic matter and nutrients simply will not produce large veggie anything. Could this be your problem?

  • Sherrie Sherrie on Jul 28, 2013
    i always prepare my soil adding compost all year long. We get it free here. I take soil samples to Missouri Extention and have them test it. Everyone should have one close it doesn't cost much to have it tested. I also follow their planting guidelines they know our area and the best planting times. I found I was following the wrong planting time for our area and my stuff either wasn't producing or I was getting very little of it. I know onions grow better in cooler weather and when the tops are laying down it is time to start pulling them.

  • Becky P Becky P on Jul 28, 2013
    I have an abundance of horse manure, my sister has horses. This year, the garden got manure and homemade compost. Thanks @Renee, for the video, can't say I would go to all that $ just to grow a few onions! lol. (all the boxed additives she added). I will admit I start my garden too early (impatient gardener, here), so I will check into the time table for starting them, also. Thanks!

  • Susan Stodola Susan Stodola on Jul 30, 2013
    There is a little difference when growing onions from plants as in the video, vs growing them from sets. When using sets, if you plant them deep, the bulb does not develop and you will have the green onions you love to pull and eat. If you just set them in the ground, say about.......1/2 the bulb, the bulb will develop into a 'large' onion. 'Large' being relative to the kind of set you are working with to begin with. All the additives do make a difference, especially if you can get some animal compost, but keeping them well watered is equally important........Also watch for that special stalk that will grow up out of the middle......it's hollow and will get an allium type flower......then little baby onions develop. When you see one of those, it's time to bend the stalks over to keep the energy directed to the bulb instead of making baby onions. Onion sets do not generally get very big, but should be bigger than a golf ball. I have used the onion plants that Renee shows in her video having no idea that they would get so big. They were a freebie from a greenhouse friend. Imagine my shock when they turned out as big as softballs!!

  • Sherry Bullard Sherry Bullard on Jul 30, 2013
    Not sure about the type of onions you are growing but this is my first year growing purple onions and Spanish onions and I have just let them grow and add fertilizer every couple of weeks because mine are in pots and mine are about the size of a small orange right now so I'm going to just keep letting them grow and just use them as needed when I cook

  • Catherine Smith Catherine Smith on Jul 30, 2013
    Susan is right. You might want to double check the varieties you are planting. You many need to try some different types to get the size you want. You also might want to check with your local extension office (look under government in the phone book) the agent or one of the Master Gardeners should certainly have some ideas or suggestions to help you.

  • Mikell Paulson Mikell Paulson on Jul 30, 2013
    You might try to plant them in pots as your garden might not be healthy enough to grow onions. My mom had a garden and rotated her veggies every year. She had a beautiful garden. She could not grow onions in it! So grew them in pots and they did very good there!

  • Becky P Becky P on Jul 30, 2013
    good idea @Mikell. Next year I am considering moving my veggie garden to the other side of the yard. (dreading that!) I have 2 trees and shrubs that are starting to shade it too much in the afternoon.

  • Sherrie Sherrie on Jul 30, 2013
    Have your soil tested. It sounds like your planting them at the wrong time. I live in SW Missouri and was planting according to that, but when I looked on my area for the planting guidelines it was listed in the Northern area not the Southwestern area. It made big difference making sure of the planting season and having my soil checked.

  • Ina Kocian Ina Kocian on Jul 31, 2013
    I had an old farmer tell me to tramp on the green part before they go to seed. This discourages the green growth and encourages the onion. I also do not plant mine deep. In fact when the roots are set, I dig out the dirt around them and let them grow on top. (I have clay based soil) I get ones as big as softballs.