Soil & potting mix
Best soil for Climbing Onion (Bowiea volubilis)
Also called Climbing Onion, Sea Onion, Zulu Potato.
More about climbing onion
About Climbing Onion
Bowiea volubilis · also called Climbing Onion, Sea Onion · houseplant
Climbing Onion is a fascinating South African geophyte with a large, green, above-ground bulb that sends up slender twining stems armed with thread-like leaves. It prefers bright indirect light, infrequent watering, and a dry rest period after the vine dies back. An unusual and easy-to-grow collectors' succulent bulb that tolerates neglect well.
Preferred mix: Well-draining succulent or cactus mix
Why climbing onion needs this mix
Climbing Onion is an easy-going houseplant — it just wants a free-draining general mix that holds some moisture but never stays soggy.
- Climbing Onion is adaptable, but like most houseplants it still needs air at the roots — a mix that drains freely while holding a working moisture reserve.
- A little perlite or bark stops ordinary compost compacting into an airless block over time, which is the slow, common cause of decline.
- It is not fussy about pH or special ingredients; getting the air-to-moisture balance right is what matters.
For the full picture on what makes up a good mix, see our guide to the main types of soil and potting media — it explains why each ingredient above behaves the way it does.
What goes wrong with the wrong mix
The wrong soil is one of the most common reasons climbing onion struggles, and the damage often shows up weeks later as a watering problem. For this species specifically:
- Plain garden soil or a cheap, claggy compost compacts in the pot and slowly suffocates climbing onion's roots.
- A pure peat mix that dries to a hard, water-repelling block is hard to re-wet and stresses the plant.
- No drainage hole turns even a good mix into a stagnant, root-rotting sump.
Reusing tired, compacted old compost or skipping the perlite. A free-draining mix in a pot with a hole solves most "why is it struggling" cases for climbing onion.
pH — does it matter for climbing onion?
Climbing Onion is not fussy about pH — a slightly acidic to neutral mix (around pH 6.0-7.0), which a standard peat-free compost provides, is perfectly fine. No testing needed.
If you want to check or adjust it, the soil pH guide walks through testing and the safe ways to nudge a mix more acidic or more alkaline.
DIY mix vs a bagged one
A decent bagged houseplant compost works for climbing onion as long as you mix in perlite for air. The simple DIY ratio above is cheap and more reliable than a budget bag alone.
Drainage and the pot
A pot with a drainage hole and a saucer you empty after watering is all climbing onion needs — the free-draining mix does the rest.
Refresh climbing onion's mix every 18-24 months; even good compost slumps and compacts, and fresh, airy mix is often the simplest fix for a tired plant. When the time comes, our repotting guide for climbing onion covers the timing and technique step by step.
Climbing Onion soil — frequently asked questions
What is the best soil mix for climbing onion?
3 parts peat-free houseplant compost : 1 part perlite : 1 part orchid bark or coco chips (optional). Climbing Onion is adaptable, but like most houseplants it still needs air at the roots — a mix that drains freely while holding a working moisture reserve.
Can I use normal potting soil for climbing onion?
Plain garden soil or a cheap, claggy compost compacts in the pot and slowly suffocates climbing onion's roots. A decent bagged houseplant compost works for climbing onion as long as you mix in perlite for air. The simple DIY ratio above is cheap and more reliable than a budget bag alone.
Does climbing onion need a special pH?
Climbing Onion is not fussy about pH — a slightly acidic to neutral mix (around pH 6.0-7.0), which a standard peat-free compost provides, is perfectly fine. No testing needed.
Should I buy a bagged mix or make my own for climbing onion?
A decent bagged houseplant compost works for climbing onion as long as you mix in perlite for air. The simple DIY ratio above is cheap and more reliable than a budget bag alone.
How often should I refresh the soil for climbing onion?
Refresh climbing onion's mix every 18-24 months; even good compost slumps and compacts, and fresh, airy mix is often the simplest fix for a tired plant. A pot with a drainage hole and a saucer you empty after watering is all climbing onion needs — the free-draining mix does the rest.
Keep reading
- Climbing Onion care — the full brief (light, water, humidity, problems, pet safety)
- How often to water climbing onion — the schedule the mix feeds into
- Repotting climbing onion — when and how to refresh the mix
- Soil pH guide — test it and adjust it safely
- Should I water my plant? The simple check first
- Overwatered plant — signs and recovery
- Root rot — how the wrong soil starts it, and how to save the plant
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- All 8452 soil and potting-mix guides in the Growli library