Inspired by the potato question, I was wondering how we optimize growth for different parts of the same plant depending on what we want.
For example: I had a yellow onion actually sprout on our countertop after a week. I thought it would be fun for the kids if we planted it in the backyard, and after a couple months it had fully grown what I guess we call green onions? So I harvested it, and the yellow onion was completely drained and squishy, used to grow the green onion part.
So how do we tell the plant, “only grow the bulb underground, don’t use that energy for growing the leafy part”, or “only grow the leafy part”?
I might also be misunderstanding all of this, but I cut off the bulb and washed/diced the green onions and they were delicious on top of our chili this week.
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The onion plant stores energy in its bulb. That’s the part we eat and consider an “onion.” However, it needs some way to gather that energy and time to collect it. That’s where the aboveground stem comes in. Think of it like a straw drinking up all the sunlight to be stored in the bulb underground. Given time, your green onions may have developed more substantial bulbs, though growing them into grocery store-style onions would have been difficult. It helps to replant the green onions so each bulb has space to expand, or just harvest some of them early, leaving a lucky few to grow bigger.
Most onion species have a “setpoint size.” They can be grown from seed, or from 1cm onion “starts” or “sets” (which are themselves grown from seed). The onion grows, half underground, half above ground, until it reaches it’s mature size. When the fall freeze occurs, the tops die off and the onion goes dormant. Commercial plantings are then dug up and shipped to market. A few varieties – such as hard yellow onions – can be stored in a cool place for months. Others like sweet onions are more perishable.
What you did was to plant a mature first season onion, one that had already completed it’s normal growing cycle the previous season. It’s already fulfilled it’s “grow to setpoint size” mandate, and all it wants to do is try and set seed. Onions (and all Alliums) are biennials – they spend one season growing, the following season setting seed, and they they die.
It might interest you to know that the onions we grow for green onions are a different variety of allium cepa species, that are bred to produce small bulbs and abundant green tops in a single season.
Onions are biennial, in the first year they produce a bulb, in the second year they produce the flower and seeds. But we harvest them to eat after the first year, as that’s when there’s a bulb.
Although we normally grow onions from sets rather than from seed, where a commercial grower has grown the seeds into small bulbs called sets which then grow to the larger bulb in a single season.
Onions grow from seed. The first year, they stockpile energy by creating a bulb. In the autumn the leafy part wilts away and the bulb overwinters. This is when onions you eat are picked from the ground. If left to their devices, the onion starts using up the bulb during the winter and then during the next year as a supplement to the newly sprouted leafy part. At the end of the second growth season they produce seeds.
Tip: pearl onions are neat and a good candidate for home growing and pickling in vinegar.
Im baffled by the downvotes on this post. This is, for once, a genuine question that can truly be answered like you are five but somehow for some people it is not quantum physics nerdy enough and doesn’t require the knowledge of hard multi generational veterans on the subject so it gets downvoted.
I want to answer a part of your question you didn’t ask and no one answered.
>what I guess we call green onions?
This is what green onions are. Except a different species of allium. Garlic, onion, green onion, chives, and similar, all look like this while growing! You can eat more than just chives and green onion stalks as well, some are tastier than others. The bulbs are also various sizes, but they still exist even for chives and green onions.
One of the fun facts about food crops is that cabbage & its “cruciferous vegetable” relatives (kohlrabi/kale/broccoli and some others) are all one species, and breeding allowed people to make what looks like different plants out of that species. But even without any generic differences at all, it’s possible to grow some plants into wildly different forms base on how they’re exposed to light/temperature/moisture. Many plants have genes that tell them to go to seed or “bolt” in particular conditions, or alternatively to grow some other part of the plant like edible roots or leaves … and to an extent farming practices may control these behaviors in the plant.
My mom always grew green beans while I was growing up. Plant some plants (or seeds) and then all season long you harvest beans.
It’s absolutely crazy for me to comprehend that something I can pull out of a big bin at a grocery store for 99 cents a pound was basically purpose grown as one onion.