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.
Most call caudatum by its common names:
- Pregnant onion
- False onion
- False sea onion
- Sea onion
Originally found in South Africa, the Ornithogalum caudatum also known as (Ornithogalum longibracteatum) has become popular, thanks to its unique characteristics.
This fascinating plant is easy to grow. Its thick succulent roots help retain water and doesn’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 to form a “bulb colony” on the mother bulb. Read on to learn more.
Pregnant Onion Ornithogalum longibracteatum Care
How Big Does The Sea Onion Grow?
An old-fashioned windowsill plant. Leaves of long green streamers for leaves.
The pregnant 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.
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 zones 4 – 10. It grows best in warmer locations but can grow indoors in cooler areas.
Flowering and Fragrance
The pregnant onion creates an unusual bloom in the spring and summer. It produces hundreds of small 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 sunlight. It should receive at least four hours of bright sunlight each day.
When planted in a container growing outdoors, move the sea onion to the ideal spot each season. In the spring and fall, it should get full sun or partial sun. 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.
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.
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 and Transplanting
For healthy pregnant onions, use a 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 tire of looking at the container. However, when transplanting, do so in the spring.
The 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: More on Allium Ornamental Onions
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 a rich soil with good drainage. When setting bulbs in soil, make sure they point upward. Set the pots in bright sunlight and water once.
Wait until the roots formed 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 Ornithogalum Caudatum 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 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 Ornithogalum Caudatum 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 in make a cold syrup.