By Erin Marissa Russell
If you’re growing onions, you’ve probably heard of a trick many gardeners claim is the ticket to growing a crop with heavy bulbs: folding, cutting, or stepping on the tops of onions. It’s true that some of the reasoning behind breaking the green tops of onions to encourage more productive bulb growth makes sense on the surface, and the advice to snap the green foliage if you want onions with big bulbs is certainly widespread.
Should I break, cut, or step on the tops of onions so they’ll grow larger bulbs?
The real gardening experts (university researchers and professionals in agricultural exchanges) disagree with the idea that breaking onion tops leads to larger bulb development. They contend that folding, breaking, or stepping on the tops of your onions doesn’t actually increase the size of their bulbs. In fact, this incredibly common gardening myth is especially aggravating because following this well-meaning but false advice will actually have the opposite of the intended effect. Stepping on the green tops of your developing onions will actually result in smaller bulbs, not larger ones.
Some of the advice encouraging gardeners to break onions tops so they’ll create larger bulbs is especially convincing because of how specific it gets. Instructions may include precise heights or time periods when the onion’s greenery should be broken, along with exactly how far the foliage should be cut back. Advocates of stepping on or cutting onion leaves to promote bulb growth say it works because breaking the foliage forces the onion to spend its resources working on its bottom half—the bulb forming underground.
While this explanation seems to make good sense, the truth is more simple. Breaking the top of the onion plant ruins the system that delivers size-building sugars to the bulb that gardeners want to grow larger. When the foliage is broken and sugar can’t be delivered to the bulb, it stops growing entirely, resulting in onions that aren’t as large as they could have been if the green tops were allowed to continue doing their job throughout the onion’s maturation period.
Skeptics may wonder why this myth is so widespread if it’s so completely false, which is a puzzling question. Perhaps the onion-cutting technique has spread based on anecdotal evidence, and well-meaning gardeners who tried this trick ended up with large onions that season for another reason entirely. Development of large bulbs in onion plants depends on adequate spacing between plants, firm control of weeds that will compete with the slow-growing onions for resources, and sufficient sunlight in the days of the onion’s growth period to allow the bulb to reach its maximum potential.
Be advised that although it’s definitely false that breaking, cutting, or stepping on the tops of onion plants causes them to grow larger bulbs, folding down the tops of onions is a different process. Gardeners fold the tops of their onions when they are nearing harvest so the onions will start the ripening process before they’re pulled.
Onions that are ready to harvest will naturally start to fold over. When you see this happening, you can fold over the tops of your onions and let them sit for a few days. This puts all the energy into maturing the bulb. Once the tops start to brown you can finish harvesting them.