Aeonium
Aeonium arboreum · Tree Houseleek
It grows on dry, sunny, rocky volcanic slopes in the subtropical Atlantic islands, in a climate that is wet in winter and dry in summer. So it keeps the strangest calendar of any houseplant: it grows in cool winter and rests through the summer heat.
Family
Crassulaceae
Origin
Macaronesia
In the wild
Volcanic cliffs
Indoors
0.3–1 m
Growth
Slow
With pets
Non-toxic
Where it's from
The Canary Islands and Macaronesia
Island cliffs
Overwhelmingly the Canary Islands, with a few on the south-west Moroccan coast, on rocky volcanic slopes facing the Atlantic.
Outdoors: zones 9–11
Grown outdoors only in mild, frost-light climates. It must come in before the cold.
Threatened island cousins
The cultivated species are abundant, but some island endemics, like A. balsamiferum and A. gorgoneum, are Vulnerable or Endangered.
It keeps the calendar backwards
Its name means ageless, from the Greek, yet each rosette flowers exactly once and then dies. And it runs the year in reverse: it grows in cool, wet winter and goes dormant in summer heat. So when other plants peak, it closes up its rosettes and waits, then comes alive again in autumn.
Grows in winter
Active in the cool, damp season and dormant in summer, the opposite of most plants.
Each rosette blooms once
A rosette sends up yellow star-flowers, then dies, while offsets carry the plant on.
The black rose is a cultivar
'Zwartkop', the near-black rosette, is the defining image of the genus in design.
How to keep it
LightFull sun to part shade
Bright light keeps the colour and tight rosettes. Harsh midday summer sun can scorch.
WaterSoak and dry
Water in its active cool season, keep nearly dry in summer dormancy. Overwatering is the main killer.
HumidityDry air is fineOrdinary dry indoor air suits it. No misting.
TemperatureMild, not frost-hardyTolerates brief light frost but bring it in before nights hit about 4°C.
SoilGritty cactus mixFast-draining and sandy. Sharp drainage is essential.
FeedingLight, growing season onlyA little feed during the active cool season is plenty.
DifficultyEasy for beginnersSimple to keep once you learn its winter-grow, summer-rest rhythm.
With petsNon-toxicNot on the ASPCA toxic list, unlike its relative the jade plant. Still, any plant can cause mild upset.
PropagationStem cuttingsCut a rosette with a few inches of stem, let it callus, then set in dry gritty mix. A topped stem regrows side rosettes.
RepottingEvery 2–3 yearsInfrequent, or when rootbound or top-heavy. Repot in its active season.
What the data says
What it costs
A common, mass-propagated succulent at the genus level, with a modest collector layer for choice cultivars.
$8–25
Prized variegated and rose-form selections, or large 'Zwartkop' specimens, run higher, but there is no inflated collector bubble here.
IUCN · Per-species, varies
In the wild
The plant you can buy for ten dollars is mass-propagated and secure, while some of its island cousins cling to single cliffsides.
The genus is not assessed as a whole. Status is per-species: the cultivated ornamentals are abundant, but narrow-range island endemics like A. balsamiferum (Vulnerable) and A. gorgoneum (Endangered) are squeezed by habitat loss and grazing on small oceanic islands.
When it sulks
Mushy, rotting stem or rootsOverwatering, especially during summer dormancy. The classic mistake.
Looks half-dead in summerUsually normal summer dormancy, not death. It perks up in autumn.
Leggy, stretched bare stemsToo little light. Top it and re-root the rosette.
Brown, scorched patchesSunburn from intense direct summer sun.
PestsAphids, mealybugs, spider mites and scale.
Varieties & company
The varieties
ZwartkopSunburstKiwiAtropurpureumRose forms
Pairs with · keep apart from
EcheveriaJade PlantHaworthiaMonsteraFernsCalathea
A new plant, every week.
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