This superb bit of Pachypodium baronii ssp. windsorii came to me some years ago from an enthusiast in Nelson who was selling a gorgeous array of seed-grown plants. I've had a couple of other Pachypodium species but have moved them on after it became apparent our conditions were unsuitable and now enjoy just this guy and the diminutive P, brevicaule. Which is supposed to be fussy and rot-prone, although no one seems to have told my plant.
P. b. windsorii is increasingly designated just 'windsorii' and distinguishes itself from the original species by its shorter stature and isolation on a couple of Madagascan massifs (including the titular Windsor Castle). It does seem to be more cold-tolerant than the classic variety, which occupies lower forests in situ.
Incidentally, I have a number of species from the Madagascan uplands and find them probably the most adaptable to our quite challenging conditions along with those from southern African hills, so if you're starting a serious succulent collection and feel you're at the edge of temperature viability for unheated cultivation, I'd point you in these two directions for your foundational plants.
> The same plant budding up at the end of spring.
P. windsorii rejoices in a fat-bootied form dressed in large stegosaurus-type spines that graduate from the base toward the growing tip, at which point it divides into plump, waxy branches, each one crowned with frangipani-like leaves in deep leathery green with a yearly burst of hot red blooms. They look as though they should emit some intoxicating perfume and I'd say this plant's only aesthetic deficit is that they do not. Oh well.
I love the way the spines seem to originate and divide laterally, as though it is mirroring itself. Weird.
Which is easy enough to do, at least in the case of P. windsorii. It's said that they like a larger root run than you'd usually allow for a plant this size, and I support this contention after constraining mine in a too-small pot for a couple of years and seeing little growth and bugger-all flowering. Restricted subsistence also seemed to make my plant more susceptible to mealy bug drama at the growing tips as well, resulting in leaf retardation. I run a strict no-spray gladiatorial policy with insect pests and either bin or move on plants that cannot prosper without toxic intervention, so it was a relief to see this guy outgrow the initial infestation this year and go on to flower non-stop for about five months after a generous repotting. Check the underside of your leaf bases on a regular basis; I squash and wipe away any mealy bullshit with a narrow hard-bristled paintbrush (the type kids use at primary school), which avoids damage to plants and keeps hands clear of spines. I find outdoor living can clear a susceptible plant of mealy bugs- just be careful not to fry a formerly sheltered specimen with too much UV and introduce it gradually to full exposure.
During the active, leafed-out summer period I've taken to giving it a generous watering every third day in lieu of rainfall and this plant seems to be happy with that amount, judging from the flowering continuity and leaf health.
As with most of my succulent collection, I use a half and half proprietary cactus soil/coarse pumice mix and (especially in the case of bulbous or globose species) take the precaution of topping off the last couple of centimetres around the plant's base with pure pumice in an attempt to fend off rot, which seems to work a treat since I've never rotted out a pachy.
Pachypodiums aren't really beginner's plants, strictly speaking, but if you've gathered a few clues about general succulent culture you should be able to manage the easier species. I'd rank P. windsorii amongst them.