Pregnant Onion Care: Growing The Unique Ornithogalum Caudatum

Pinterest Hidden Image

The ‘Pregnant Onion” – Ornithogalum caudatum [or-ni-THOG-al-um] [kaw-DAY-tum] is a bulbous flowering plant belonging to the Asparagaceae family. The family is known famously for the asparagus plant.

pregnant onion with the new bulblets formingPin
Pregnant Onion Ornithogalum Longibracteatum has a shallow root system

Most call caudatum by its common names, such as:

  • Pregnant onion plant
  • False onion
  • False sea onion
  • Sea onion

Originally found in South Africa, the Ornithogalum caudatum also known as (Ornithogalum longibracteatum, Ornithogalum bracteatum, and Albuca bracteata) has become popular thanks to its unique characteristics.

This fascinating plant is easy to grow. Its thick succulent roots help retain water and don’t face any significant diseases or pests.

Where Did The Name ‘Pregnant Onion” Come From?

This plant earned the name “pregnant onion” because of the bulblets forming in spring below the outer layer of the mother plant bulb.



The baby bulbs swell and remain attached, forming a “bulb colony” on the mother bulb. Read on to learn more.

Ornithogalum Quick Care Tips

  • Botanical Name: Ornithogalum Caudatum
  • Common Name(s): Pregnant Onion, False Sea Onion
  • Synonyms: Ornithogalum longibracteatum, Albuca bracteata
  • Family & Origin: Asparagaceae family, native to South Africa
  • Growability: Easy to grow
  • Grow Zone: USDA zones 4-10
  • Size: Grows up to 2′ feet tall
  • Flowering: Produces small white flowers on a tall stalk
  • Light: Prefers bright, indirect light
  • Humidity: Tolerates low humidity
  • Temperature: Thrives in temperatures between 60-80°F
  • Soil: Well-draining soil
  • Water: Water thoroughly when soil is dry to the touch
  • Fertilizer: Fertilize once a month during growing season with a balanced fertilizer
  • Pests & Diseases: Susceptible to mealybugs and spider mites. Watch for root rot if overwatered.
  • Propagation: Propagated by separating offsets from the main bulb
  • Plant Uses: Grown as a houseplant or in outdoor gardens. The bulb is edible and can be used in cooking.

Ornithogalum Longibracteatum Pregnant Onion Care And Growth Requirements

How Big Does The Sea Onion Grow?

An old-fashioned windowsill pot plant. Leaves of long green streamers for leaves.

The pregnancy onion produces unusual growth. The large green bulbs reach up to 4″ inches in size.

Long, strap-like leaves sprout from the top of the main bulb and reach about 2′ feet tall. In ideal conditions, the leaves can reach five feet.

Green plant with bulbous base and budding pods.Pin
Photo Credit: Instagram @arch.gully

The pregnant onion is such a visually appealing and easy-to-grow houseplant, preferably for first-timers.

The plant grows at a medium rate and is easy to contain in a pot or planter. 

The recommended growing zones for the “Pregnant Onion” is USDA hardiness zone 4 – 10. It grows best in warmer locations but can grow indoors in cooler areas.

Pregnant Onion Flower and Fragrance

Pregnant onion plants create an unusual bloom in the spring and summer. It produces hundreds of small white flowers on a spike sitting atop a two-foot tall stem.

These small green and white star-shaped flowers offer a light, pleasant scent.

Light and Temperature

This subtropical plant needs lots of direct sunlight. It should receive at least four hours of bright sunlight each day.

But then, if you’re looking to have more radiant foliage, it’s far much better to put the growing medium indoors under warmer temperatures.

When planted in a container growing outdoors, move the sea onion to the ideal spot each season. It should get full or partial sun in the spring and fall. In the summer, it should receive partial shade.

When growing indoors, any window receiving bright sunlight throughout the day should work. A south-facing window is often the best choice.

It is generally a low-maintenance plant and is best grown indoors in a sunny window or outdoors in an area with some afternoon shade.

Normal room temperature (72° degrees Fahreinite) is fine for this plant indoors. It can’t survive a freezing winter outdoors.

Watering and Feeding

Pregnant onions need regular watering but not soggy soil. Allow the soil to dry between watering.

 When this species receives too much water, its stems and leaves may begin to wilt and turn from green to yellow. 

In the winter, reduce watering. Supply enough water to help keep the bulbs from shriveling.

Fertilize in the spring, summer, and fall, adding water-soluble liquid fertilizer to the water before watering. Don’t fertilize in the winter.

Soil Requirements and Transplanting

Soil requirements are minimal, with adequate drainage being the most crucial factor. 

Traditional potting soils should be avoided, as they tend to retain moisture. Preferred choices include using pure construction sand or a blend suitable for cacti or orchids. 

For healthy pregnant onions, use rich, well-drained soil. You can use regular potting soil with additional perlite added.

The bulb sits or grows above ground on top of the potting mixture.

Repotting is only needed if you get tired of looking at the container. However, when transplanting, do so in the spring.

Springtime is also the right time to look for new bulbs growing off the older bulbs.

Grooming and Maintenance

While grooming is not required for this unique plant, there is one task you will want to perform.

As the outer layers of the bulbs start to dry and peel off, remove them. This helps encourage healthy growth throughout the growing season.

Related Reading:

How To Propagate Ornithogalum longibracteatum

Propagate plants by separating new bulbs from the larger parent bulbs. Easily remove these bulbs without damaging the parent bulbs.

Place the younger bulbs in individual pots using rich soil with good drainage. When setting bulbs in the soil, make sure they point upward. Set the pots in bright sunlight and water once.

Wait until the roots form before watering again. When the plant takes root, move the bulb to a larger pot. With proper care, these young bulbs may last for several years.

What Pests or Disease Problems Does False Sea Onion Encounter?

This hardy plant doesn’t have any significant threats, but there are a few issues to look for. You may notice mealybugs on the plant. They typically hide between the leaves.

TIP: To remove mealybugs, use a cotton swab dipped in alcohol. Wipe the bugs away. For a larger infestation, spray the plant with insecticide.

If you notice bulbs loose in the soil, it may be time to get rid of the older bulbs. Collect the younger bulbs and replant them while tossing the older bulbs.

The bulbs may also start to rot, which is typically a sign that the soil is too wet. If you notice orange-brown patches on the leaves, the plant is getting too much sunlight.

Suggested Sea Onion Plant Uses

This unusual plant is a great conversation starter. If grown indoors, set it somewhere guests can see it. Make sure it still receives enough sunlight.

A hanging basket is also a great option for this plant, as the basket allows the leaves to cascade over the sides.

As a medicinal plant, it is known as the German onion. Residents of the German countryside used crushed leaves to cauterize cuts and bruises. It was also cooked with rock candy to make cold syrup.

JOIN Our FREE Plant Care Newsletter 

By entering your email address you agree to receive a daily email newsletter from Plant Care Today. We'll respect your privacy and unsubscribe at any time.