How to Grow and Care for Climbing Sea Onion Plants

Bowiea volubilis climbing sea onion plant

Robert Knapp / Getty Images

The Climbing Sea Onion Plant (Bowiea volubilis) is not really an onion nor is it edible. Part of the Asparagaceae family, it is not related to the onion or alliums at all; in fact, the plant has green string-like foliage reminiscent of ornamental asparagus ferns and edible asparagus. Hardy in USDA Zones 10 and 11, this bulbous succulent is a tropical, tender perennial. This plant grows from a bulb 8 inches wide in its native habitat, 4 inches wide in pots. Only about 10 percent of the bulb actually remains in the soil. From the base, the roots reach down into the soil. Slender stems come from the bulbs and branch out about 2 feet tall into feathery stalks. A fast-growing, twining, rambling vine emerges. Along the stems numerous flowers of greenish-yellow and white appear, forming delicate 6-pointed stars, from January through March.

Botanical Name Bowiea volubilis
Common Names Climbing Sea Onion, Climbing Onion, Sea Onion​, Zulu Potato, Climbing Potato
Family Asparagaceae
Plant Type Bulb, vine, succulent
Mature Size 2 ft. tall, 4 to 8 in. wide
Sun Exposure Full, partial
Soil Type Silt, well-drained
Soil pH Acidic, neutral (5.0-7.0)
Bloom Time Winter, spring
Flower Color Green, yellow, white
Hardiness Zones 10, 11
Native Area Africa
Bowiea volubilis (climbing onion, sea onion) is of the Asparagaceae family.
Paul Starosta / Getty Images

Climbing Sea Onion Care

This tender perennial enjoys soil meant especially for succulents, plenty of light, and warm temperatures. Treat it much like an African violet and take care to not overwater--but also don't let the soil dry out. With good care, this unique plant—also known as Zulu Potato or Climbing Potato—can give you many years of visual interest.

Light

If kept as a houseplant, the Climbing Sea Onion can be moved outside in full, sheltered summer sun where temperatures remain above 50 degrees Fahrenheit.

Soil

Establish in gritty, well-drained soil such as cactus mix, or a mix of half potting soil and half sand.

Water

During the growing season, water well but do not overwater. Allow for moderate, consistent moisture but don't let the soil dry out. Given proper care and conditions, the bulb should re-sprout in the fall. Resume watering as normal.

Temperature and Humidity

Akin to its native South Africa, the plant thrives best in warm temperatures but moderate humidity. If temperatures are too hot, the bulb calluses over and becomes dormant.

Fertilizer

The plant does not require fertilizer, as long as the bulb continues to produce well. The bulb stores carbohydrates that allow for continual plant growth.

Types of Climbing Sea Onion

This unique plant hails from Africa and has two subspecies: Bowiea volubilis subsp. gariepensis, which has shorter stems and thicker leaves. It tends to bloom in the fall. The other subspecies, Bowiea volubilis subsp. volubilis, is widely used in Africa for medicinal purposes.

Pruning

After it stops blooming, the stalks will dry and the plant will go dormant in late summer. Cut off the stems as they brown. If the foliage dries out during the growing season, cut back and let new growth appear.

Propagating Climbing Sea Onion

Divide every five years if the soil needs replenishing. Most Climbing Sea Onion plants are propagated clonally, so seed set rarely happens.

The more common means of propagation is to divide and repot smaller bulbs produced by the maturing plant in late summer and fall. Like most bulbs, climbing onion bulbs branch at their base and slowly produce "new daughter bulbs."

Another means is to cut the thick outer peel of the bulb scale from the mother bulb. Cut into two or three sections. Place on moist potting soil and wrap the container in a plastic bag. This is quite the test of patience. Small pea-sized bulblets may form in three to four months.

How to Grow Climbing Sea Onion From Seed

If you propagate or buy seeds, sprinkle them on top of the soil and cover with 1/4 inch of white pumice. Seeds will need warmth, light, and daily waterings to germinate and develop bulbs.

Potting and Repotting Climbing Sea Onion

Give this bulbous succulent a pot only slightly larger than the bulb that has drainage holes (too much moisture can cause the bulb to rot). The plant actually prefers to be in a crowded container. Establish the growing vine on a 2-foot-tall trellis. Unlike most vines that twine around structures, Climbing Sea Onion grows upwards and tangles on itself and on other nearby plants or structures. Consider offering it a companion plant that will serve this purpose such as a small shrub.

Overwintering

If grown in the garden in zones 10 or 11, this plant is winter dormant and needs only a good layer of mulch to help protect it from cold snaps. If growing in pots, make sure the temperature never dips below 50 degrees Fahrenheit where the plants are kept as temperatures lower than that can kill them.

Common Pests and Plant Diseases

Fortunately, climbing sea onion isn't prone to attracting pests. The only plant disease that could become a serious problem seems to be root rot, a problem that can be solved with adequate drainage and care in watering.

FAQ
  • How long does climbing sea onion live?

    When given the ideal conditions, climbing sea onion has been known to survive for 20 years or more.

  • Can climbing sea onion grow in gravel?

    Though climbing sea onion is considered a succulent and many home gardeners attempt to use gravel as a medium, growing it in gravel doesn't provide enough nutrients to sustain this unique plant and will shorten its lifespan.

  • Where should I place climbing sea onion in my house?

    You will want full but sheltered sun for your plant, though partial shade is also okay. A windowsill that gets some full sun in the morning and shade in the afternoon is a good idea.