Alluaudia is a spiny succulent shrub from Madagascar that most people meet under the name Madagascar ocotillo. It has the architecture of a desert plant taken to an extreme: tall, near-vertical stems armoured with spines, small round leaves tucked in beside each spine, and, in summer, small yellow or green flowers in a rounded umbel-like head. It grows from 1-10 m (3-30 feet), is hardy in zones 9-12a, and it is slow – which shapes almost every decision you make about it.
Is it really an ocotillo?
No, and the difference is worth knowing before you buy. The true ocotillo of the American southwest is Fouquieria splendens, an unrelated plant. Alluaudia only looks like it. Both are tall, whippy, spine-covered stems that carry small leaves seasonally and drop them in drought – a classic case of two lineages arriving at the same solution to the same problem in two different deserts.
The practical consequence: care instructions written for the American ocotillo are not a safe guide here. Alluaudia comes from the spiny forests of southern Madagascar, is toxic, and is more tender than the desert-southwest look suggests.
Drainage first: the one thing that kills Alluaudia
The soil requirement is short: drained soil. Everything about the plant follows from that. Its whole growth strategy is to store water in thick stems and survive long dry spells, so the roots are adapted to soil that dries out quickly between soakings. Leave them in wet ground and they rot, and rot in a succulent stem travels upward.
- Plant into gritty, sharply draining soil – a raised bed, a slope, or a mineral-heavy container mix.
- Water only a small amount, and let it dry properly before the next drink.
- Be especially careful in summer. When you plant in the hot season the plant needs enough water to root in but is at its most vulnerable to overwatering – our own notes flag exactly this balance, “careful to not too much water and not enough water”.
Light and climate
Grow it in full sun to half shade. Full sun gives the densest, sturdiest stems; half shade is tolerated and can be useful in a fiercely hot, dry position. It suits desert, mediterranean and subtropical climates, and hardiness zones 9 to 12a – zone 9 is defined by an annual low of about -7°C (20°F), so realistically this is a frost-free or near-frost-free plant. Below that range it has to be a container plant that comes indoors or under cover, or a greenhouse specimen.
Support the stems – this is not optional
The most useful piece of care advice for Alluaudia is also the least obvious: support the stems so they cannot fall. A tall succulent stem is heavy with stored water and structurally weak compared with a woody trunk, and once it starts to lean it keeps going. A fallen stem on this plant is a real problem, because the whole thing is covered in spines – you cannot simply grab it and lift it back, and dealing with it after the fact means gloves, padding and a genuine risk of injury.
Stake early, while the plant is small and light. Use broad ties rather than thin wire, which cuts into soft succulent tissue. Check the ties as the stem thickens.
It is toxic – handle accordingly
Our growing notes list toxic as the plant’s main difficulty. Combine that with the spines and the sensible routine is: thick gloves and long sleeves for any pruning, keep cut surfaces and sap off your skin and away from your eyes, wash tools and hands afterwards, and site the plant where children and pets are not brushing past it. It is a superb sculptural specimen for a gravel bed or a courtyard corner; it is a poor choice for a narrow path.
Pruning: cutting out rot
You can prune all year, because pruning here is not about shaping to a season – it is about removing damage before it spreads. The rule from our notes is precise and worth following exactly:
- Find the rotten or infected section. Soft, discoloured or collapsing tissue on an otherwise firm stem.
- Cut one centimetre below the infected area, into clean, firm, healthy tissue. Rot runs ahead of what you can see, so cutting at the visible edge leaves infection behind.
- If the cut face still looks discoloured, cut again, lower, until it is clean.
- Use a clean blade, and clean it between cuts so you do not carry the problem to healthy stems.
- Let the wound dry and callus in the air. Do not water heavily straight afterwards.
Propagation: seed, cuttings or a bought plant
You can start Alluaudia from a plant, from seed, or vegetatively. Grafting is not necessary, though vegetative propagation is easy and is the fastest route. Seed is genuinely easy to germinate – the catch is not germination, it is time. This plant is slow growing, so a seedling is a project measured in years, and buying an established plant or rooting a cutting gets you to a presentable specimen far sooner.
From seed
- Sow in drained soil in full sun.
- Sow at 0.5 cm deep – shallow.
- Give a small amount of water and do not overwater. Damp, not wet, is the target; seedling succulents damp off very easily.
- Sow from spring through to autumn. Spring is best because the seedlings get a full warm season to build roots.
- If you sow in autumn, protect the seedlings over winter. They are small, they have no water reserves yet, and cold wet conditions will finish them.
From cuttings
Take a stem section, let the cut surface dry and callus before it goes anywhere near soil, then set it in the same gritty, fast-draining mix and keep it barely moist until roots form. Callusing first is what stops the cut end rotting – the same principle as pruning out infected tissue and letting the wound dry.
Planting season
Plant in spring or autumn for the easiest establishment. Summer planting is possible but demands more attention to watering, for the reason above. Spring is the safest choice in most gardens: warm soil, a long growing season ahead, and no risk of a cold wet spell hitting a plant that has not rooted in yet.
Growing in containers
Container growing works well, and in any climate colder than zone 9 it is the only realistic option. Use a wide, stable, heavy pot – a top-heavy spiny plant in a light plastic pot will tip, and you now have the fallen-stem problem indoors. Use a mineral, free-draining mix, water sparingly, and put it in the brightest position you have. Note that Alluaudia is not suited to life as an ordinary houseplant; a container plant should live outdoors in the warm months and come in only to escape cold.
Flowers
Flowering is in summer. The flowers are small and yellow or green, carried in an inflorescence shaped like an umbel or a ball. They are a pleasant detail rather than the reason to grow the plant – the stems and spines are the display, and they are on show all year.
For the full plant profile see our Alluaudia growing page.
