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.
