September 11, 2015

Urban Gardening: Growing Onions (Part 1)

For your reference, here is a list of entries under the Urban Gardening series:

To add some variety to my balcony garden, I decided to plant some onions. Onions are a mainstay in the circulating lists of vegetables you can grow using kitchen scraps. There's nothing much to do while waiting for my tomato seedlings to grow strong, so perhaps it's time to take on another gardening project.

Day 0: Callousing the onion bottoms

The regrow-able part of the onion is its bottom part, consisting of the roots plus half an inch or so of onion flesh. A fresh onion vegetable is quite juicy after slicing, so it is quite important to let the onion bottoms dry for a day or two before planting them into the soil.

Just your garden variety yellow onion.

Day 1: Planting the calloused onion bottoms 

Onion bottoms that have dried nicely should exhibit curling and separation of the onion's fleshy layers. Notice that some onions will have more than one "center." Each center is a potential onion plant, which means that the bulb is expected to form from them.

The onion bottom on the upper right shows a perfectly
calloused onion bottom.

Now, plant these calloused onion bottoms in a starter pot, with enough soil just barely covering the onion parts. This is not the final container of the onion as it needs to be transplanted at least one more time.

You can hardly see any onion parts, but don't plant too deep.

Day 6: Shoots start to appear

Leaving the onion bottoms by a sunny window, the onion shoots will start to appear. Each of the "center" in the onion bottom will sprout a couple or so onion shoots.

The onion shoots are thick, but fragile as they are hollow inside.


  • Do not over-moisten the soil as onion bottoms have a high tendency to rot due to humidity.
  • Onion bottoms, being portions of an edible vegetable, are very attractive to egg-laying flies and other insects. I've lost a couple onion bottoms in this stage because they have been infected with maggots. Take precautionary measures to ensure that the soil will not harbor insect larvae.

Day 9: Transplanting the onions

Give the onion bottoms a couple more days for the shoots to grow to a sturdy height. Once satisfied with the growth of the shoots, carefully dig them out of the starter pot.

Looking good for transplanting, little onion bottom!

If there are more than one shoot growing from the onion bottom, separate them using a sharp knife. Ensure that each separated shoot includes a part of the root system growing under the onion bottom.

Two shoots in one onion bottom, separated using a knife.

Then, plant the onion shoots in a larger container, this time a little more deeply. Bulbs are expected to form from these shoots, so plant at a depth that you envision the size of your bulb to be.

The crucial part: protecting your onions from pests

Growing strong?

Unfortunately, I still wasn't able to grow a successful onion bulb. I would always find the leaves wilting a week after transplant, with most of the root bulb consumed or rotten. Little flies would fly out the soil when I dig up the remains of my wilted onion. I haven't explored the option of using insecticides on my garden, but it seems that I should start soon lest I suffer fly infestation on my balcony.

Hopefully the next time I blog about the progress of my onions, I am able to present a picture of my first harvest. Green fingers crossed!

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