Senecio crassissimus Humbert is the vertical leaf or airplane plant. It belongs to the group that has remained in Senecio sensu stricto under the reclassifications. The common names refer to its striking habit of orienting flat paddle leaves vertically, edge-on to the midday sun.
Native to southern and western Madagascar, where it grows in seasonally dry scrub on rocky substrates. Part of the Complete Senecio Guide.
Identification
- Upright semi-shrub, 45–60 cm tall at maturity.
- Leaves flat, ovate-oblong, 3–5 cm long, grey-green with a waxy bloom and a distinct reddish-purple margin.
- Leaves attached to the stem at an angle that positions the blade plane vertically, minimising midday solar gain.
- Flower heads yellow, in loose terminal clusters on leafless peduncles.
The vertical leaf orientation is diagnostic. No other common succulent in cultivation holds its leaves this way.
Cultivation
A good beginner's succulent for bright outdoor positions. Where it diverges from the pillar's general guidance:
- Light. The vertical-leaf trick only works under strong overhead light. In dim conditions the leaves drop flat and horizontal, losing the characteristic silhouette. Full sun outdoors, brightest available window indoors.
- Water. Tolerates somewhat more water than the Curio trailers; the thick stem and taproot buffer short dry-wet cycles well. The standard indoor 10–14 day schedule is appropriate.
- Substrate. Ordinary gritty succulent mix. Less fussy than bead-leaved species.
- Cold. Frost-sensitive; leaves burn below −1 °C, though the stem often resprouts from the base if the roots escape freezing.
Etiolation in low light is obvious and reversible by beheading. The cut stem resprouts along its length.
Propagation
Stem cuttings are reliable. Take a 10–15 cm section, remove the lower leaves, callus for three days, and insert into dry substrate. Roots form within two weeks.
Leaf propagation is unreliable here as with most Senecio; occasionally a detached leaf forms a small plantlet at the base, but success rate is under 20%.
Notes and quirks
The red leaf margin intensifies under strong light and cool nights, and fades to green in shade or heat. A well-lit autumn specimen can show almost crimson edging; the same plant moved indoors for winter reverts to plain grey-green within weeks.
S. crassissimus is frequently sold as the ancestor of a range of upright cultivars and trade names, including "Mount Everest", "Skyscraper", and sometimes "Himalaya". Many of these are simply well-grown specimens of the species selected for height. See the Senecio 'Skyscraper' satellite and the Senecio 'Himalaya' note.
Mildly toxic to pets and livestock.
See also
- Senecio 'Skyscraper' — tall-stemmed trade selection.
- Senecio barbertonicus — another shrubby true Senecio.
- Senecio articulatus — candle plant.