Do Onions Grow Underground

When answering the question about whether onions grow underground, the answer is ambiguous. The bulb of the onion grows underground, but the onion tops grow above ground. Gardeners harvest yellow onions and red onions for their bulbs, which would be underground. On the other hand, you harvest green onions for their stalks, which grow above ground.


Growing Underground Onion Bulbs

When you’re ready to plant your onion bulbs or seedlings, test your soil first. It should test as slightly acidic and contain organic matter that’s full of nitrogen. Make sure your garden soil drains well before planting your onions. Add organic matter or organic fertilizer to your soil, if it lacks sufficient nutrients. Follow these steps for planting your onion bulbs or transplants:

  • Dig furrows in your garden soil that are 1 to 1.5 inches deep and in rows that are 1 to 1.5 feet apart.
  • Place the onion bulbs in the furrows, separating them by 3 inches.
  • Cover the bulbs with loose soil, allowing the tops to stick out.
  • Water the onions until the soil is moist without forming puddles. You can also spread mulch around the onion bulbs to conserve water.
  • Harvest your underground onions when the onion stalks start to yellow and fall over.

Growing Onion Tops above Ground

You grow onion tops following the same procedure as growing underground onion bulbs. The only difference is that you’ll harvest the onion tops, instead of the bulbs. The green onion stalks will grow within two weeks from the time you plant the bulbs. All you have to do is cut off the stems that your need and more will grow.

Growing Green Onions in Containers

You can also grow green onions in containers, leaving them in the house, rather than outside in the garden. If you decide to use containers, choose one that is about 6-inches deep. Fill the container about half-way with nutrient rich soil. Place your green onion bulb in the soil and cover it with soil. Keep the soil moist, and place the pot in a window that gets sun most of the day. Trim off your green onions whenever you need them.