Everything about the Onion Plant


Common Name: Onion

Latin Name: Allium cepa

Family: Amaryllidaceae

Plant Time: -

Mature Size: 12–18 in. tall, 6–12 in. wide

Sun Preference: Full sun

Soil Preference: Loamy, well-drained, neutral soil

Bloom Time: Summer

Flower Color: purple, white, red

Native Area: Asia

Toxicity: Toxic to pets

Growth Rate: -

Wildlife Value: -

Table of Contents

The onion plant, (Allium cepa), is a biennial bulb closely related to garlic, shallots, and chives. Its leaves are blue-green and tubular, emerging from a bulb that consists of numerous modified leaf structures.

It has a shallow root system and may push partially above ground as it matures. With its moderate growth rate, it is typically planted in the spring using seeds, transplants, or sets. However, it’s important to keep in mind that onions can be toxic to pets due to their chemical compounds, so careful consideration should be taken when deciding where to plant them.

Most common Onion varieties:

  • Ailsa Craig
  • White Grano
  • White Grano
  • Italian Torpedo
  • Red Burgundy
  • Utah Yellow Sweet Spanish
  • Walla Walla


The three most important things when it comes to caring for Onions are to provide full sun for at least six hours daily (like the Eucalyptus plant), use well-drained soil with organic matter and a neutral to slightly acidic pH, and water regularly but avoid overwatering or allowing the bulbs to sit in soggy soil.

  • Soil: The key is to give it proper soil that is well-drained, sandy, and rich in organic matter. A loose loam is suitable, and a neutral to slightly acidic soil pH is optimal.
  • Water: Onions require regular watering (just like pumpkins) to support bulb growth, with a recommended 1 inch of water per week. Overwatering or allowing the bulbs to sit in damp soil can cause bulb rot. A light layer of mulch can help to maintain soil moisture.
  • Light: For proper growth, onions require a minimum of six hours of direct sunlight per day. The more sunlight the better.
  • Temperature: Onion seeds require temperatures above 40 degrees Fahrenheit to germinate, and the ideal temperature range for onion growth is between 68 to 77 degrees Fahrenheit. As long as soil moisture needs are met, you don’t have to worry about humidity levels.

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Onions can be propagated from seeds, sets, or scraps. Propagating onions from scraps is a great way to reduce waste and extend your harvest.

To do this,

  1. cut an inch off the bottom of the fresh onion, remove the outer skin, and let it dry out for a day.
  2. Place the root side down in moist soilless potting mix, cover with soil, and keep in a warm, bright spot.
  3. Keep the soil moist but not soggy. In two weeks, green leaves and roots should emerge.
  4. Once the leaves are several inches long and the roots are well-developed, transplant the onion.

Check out our full guide on Growing Onions!

Common Pests

Frequently Asked Questions

Can I grow onions from an onion?

Yes, you can cultivate your own onions from cuttings by cutting off the bottom of an onion bulb and planting it into the soil.

Do onions need full sun?

Yes. Onion plants love sunlight, so you are going to need lots of it if you want to grow them.

Do onions need a lot of water?

Onion plants need 1 inch of water every week, but the best way to see if you need to water them is by checking their soil. If it is dry, it is time for a shower.

Are onions toxic to cats?

Yes. Unfortunately, the chemicals in the onion plant are toxic to pets.

Do onions need a lot of soil?

To grow onions in a container, it’s important to ensure that the container is deep enough, with at least 10 inches of soil depth. The width of the container can be as large as possible, depending on the available space.