The Climbing Sea Onion Plant (Bowiea volubilis) is not really an onion. 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. This tender perennial is also known as simply Climbing Onion or Sea Onion, Zulu Potato, Climbing Potato, as well as "igibisila." "gifisila," "umagaqana," and "knolklimop" in its native regions of South Africa through Kenya. Hardy in USDA Zones 10 and 11, this bulbous succulent is a tropical, tender perennial.
This plant grows from a bulb eight inches wide in its native habitat, four 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 two feet tall into feathery stalks. A fast growing twining, rambling vine emerges. Along the stems numerous flowers of greenish yellow-white appear, forming delicate six-pointed stars, from January through March. Learn to care for this plant on an outdoor patio or in an indoor sunroom.
|Botanical Name||Bowiea volubilis|
|Common Names||Climbing Sea Onion, Climbing Onion, Sea Onion, Zulu Potato, Climbing Potato|
|Plant Type||Bulb / Bulbous succulent|
|Mature Size||Two feet tall, four to eight inches wide|
|Sun Exposure||Full, but sheltered, sun or partial shade|
|Soil Type||Gritty, well-drained (half potting soil, half sand)|
|Soil pH||Acid to neutral, 5.0-7.0|
|Bloom Time||January through March|
|Flower Color||Greenish yellow-white|
|Hardiness Zones||10, 11|
|Native Area||South Africa, Zimbabwe, Zambia, Tanzania, Uganda, Kenya, Mozambique, Malawi, Angola|
How to Grow Climbing Sea Onion Plants in Containers
Give this bulbous succulent a six-to-eight-inch pot that has drainage holes (too much moisture can cause the bulb to rot). The plant actually prefers to be in a crowded container that is just larger than its bulb. Establish the growing vine a two-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.
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.
Establish in gritty, well-drained soil such as cactus mix, or a mix of half potting soil and half sand. Akin to its native South Africa, the plant thrives best in warm temperatures but moderate humidity.
During the growing season, water well but do not overwater. Allow for moderate, consistent moisture and let the soil dry out between watering much as you would for an African Violet.
After it stops blooming, the stalks will dry and the plant will go dormant in late summer. Cut off the stems as they brown. Keep dry.
Give proper care and conditions, the bulb should re-sprout in fall. Resume watering. If the foliage dries out during the growing season, cut back and let new growth appear.
According to North Carolina Extension Gardener, the Sea Onion is toxic if consumed in large quantities. The bark, flowers, fruits, leaves, roots, seeds, stems are all mildly poisonous. Minor skin irritation, especially of wet skin, lasts a few minutes. Nausea, vomiting, diarrhea, abdominal pain, cramping, and slow pulse can also occur.
Divide every five years if the soil needs replenishing. Most Climbing Sea Onion plants are propagated clonally, so seed set rarely happens. If you do propagate or buy seeds, sprinkle them on top of the soil and cover with a quarter-inch of white pumice. Seeds will need warmth, light, and daily waterings to germinate and develop bulbs.
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.
No wonder the Climbing Sea Onion is beloved as a "curiosity specimen." Experiment with all its ways of propagation and more. Enjoy this distant relative of the lily for its asparagus-like foliage, rambling vine, and tender yet versatile nature for years to come.