Fouquieria columnaris
| Light | Full sun to very bright light; acclimate gradually to avoid scorch |
|---|---|
| Water | Sparingly; water during its cool-season growth and keep dry through hot summer dormancy |
| Soil | Very fast-draining, gritty mineral mix (see Soil and potting mix) |
| Temperature | Tolerates light frost when dry; USDA zones 9b–11 |
| Propagation | Seed (primary); very slow |
| Toxicity | No significant toxicity reported |
Fouquieria columnaris is a bizarre, slowly tapering columnar succulent tree from the deserts of Baja California, Mexico, prized among collectors as one of the strangest of all pachycaul plants. Its thick, water-storing pachycaul trunk rises like a fat, upside-down carrot studded with short spiny branches, and in older plants it can reach many metres tall while twisting and forking into surreal shapes. These features have earned it the common names boojum tree — coined after the imaginary creature in Lewis Carroll's The Hunting of the Snark — and cirio (Spanish for "candle"), and it remains one of the most sought-after slow-growing succulents in cultivation.
Description
Fouquieria columnaris forms a stout, tapering pachycaul trunk that is broadest at the base and narrows toward the top, giving mature plants their distinctive candle- or carrot-like silhouette. The soft, water-storing wood is clad in a pale bark, and from all along the trunk sprout numerous short, wiry lateral branches armed with spines. Old specimens in habitat can reach well over 10 m tall, sometimes bending, arching, or fusing into fantastical forms, though potted plants stay far smaller and grow at a famously slow pace.
Like its relatives, the boojum is drought-deciduous: small leaves flush from the branch spines when moisture and cool temperatures allow, then drop as conditions dry. Creamy yellow, honey-scented flowers are borne in clusters near the top of the plant, typically in the warmer part of the year, and are pollinated by insects in the wild.
Distribution and habitat
The species is essentially endemic to the central desert of Baja California, Mexico, with a small disjunct population across the Gulf of California in coastal Sonora (the Sierra Bacha). It grows on rocky slopes, granitic soils, and coastal desert flats in an arid, fog-influenced climate, where most of its meagre moisture arrives in the cooler months.
Because of this rhythm, the boojum is largely a cool-season grower, leafing out and putting on growth when temperatures drop and rains or coastal fog arrive, then going dormant and dropping its leaves through the heat of summer. Its habitat is remote and slow to regenerate, so wild plants and seed are best left undisturbed; like all cacti and many succulents traded internationally, Fouquieria is subject to conservation regulation, and nursery-grown, seed-raised plants are the responsible source (see CITES).
Cultivation
Fouquieria columnaris is a rewarding but demanding subject that tests a grower's patience. Give it full sun or the brightest light available, and plant it in an extremely free-draining, gritty, mostly mineral mix in a pot with generous drainage. The single most important thing is to match watering to its unusual seasonal rhythm: water while the plant is in leaf and actively growing in the cooler months, then reduce sharply and keep it dry and warm during summer dormancy, when excess moisture readily causes rot.
The boojum resents cold, wet conditions but will tolerate light frost when kept dry, making it best suited to warm, arid climates or a bright greenhouse elsewhere. Move seedlings and imports into stronger light gradually to avoid scorching the soft bark. See Watering and Repotting for general technique, and expect only a little growth each year — this is a plant grown for the long haul.
Propagation
Seed is the standard and most reliable method. Fresh seed sown on a warm, gritty, well-aerated surface and kept lightly moist will germinate, after which seedlings must be grown slowly and never kept soggy. Cuttings are difficult and rarely successful, so vegetative increase is uncommon. Because seedlings are so slow, most growers simply raise plants on from seed over many years. See Propagation — seed for a full walkthrough.
Common problems
- Rot — by far the biggest killer, caused by watering during summer dormancy, a slow-draining mix, or cold-and-wet winter conditions; the trunk softens and discolours.
- Leaf drop out of season — usually a normal response to heat or drought as the plant enters dormancy, not necessarily a sign of trouble.
- Sunscald — soft, freshly imported, or shade-grown plants can scorch if moved into intense sun too quickly.
- Pests — scale and mealybugs may shelter among the spines and branch bases; inspect regularly (see Pests and diseases).
See also
- Fouquieria — the genus overview
- Soil and potting mix · Watering · Repotting · Propagation — seed
- CITES