Our resident Pittocaulon praecox or palo loco (crazy pole/tree) is flowering for the first time this year. The Latin translates as "pitch-stemmed early one."
The genus Pittocaulon has been recently split from Senecio, a whale of a genus still containing over 1200 species. Members of Senecio have a wide range of forms: arid zone succulents to aqautics; annuals to perrenials; climbers, trees and small shrubs.
Pittocaulon contains five species indigenous to central and southern Mexico. They are shrubs or small trees with broomsick/pole-like branches that lose their leaves during the dry season (or winter in cultivation here in NZ). Pittocaulon occur over a diverse range of habitats, from dry scrub at 3000 meters to dry tropical forest at 300 meters. P. praecox has the widest range in the genus.
Both the Latin and common names refer to the phenology (specifically flowering) of P. praecox. In the wild the crazy-pole (as with some other members of Pittocaulon) flowers at the end of a dry season when the flora is under severe water stress, well before any of the other associated plants. This seemingly risky investment in early flowering ("early" = prior to the onset of rainfall) may give the crazy-pole an edge on its neighbours when it comes to competing for pollinator attention; Being the only show in town presumably bolsters patronage. I don't imaging insects are particularly abundant at this time of year either, but if exclusive access to pollinators really has driven selection for early flowering, then the book-keeping should work out in the crazy-pole's favour.
*Medicore plant-porn to follow*
Apologies for the mediocrity of some of the following pics. This plant is really hard to satisfactorily photograph without some kind of rudimentary studio set-up, which i do not possess.
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| Crazy-pole at the beginning of flowering |
The following photos chart the emergence of the inflorescence, a corymb.
The next sequence shows the opening of a single P. praecox capitulum. Capitula are a type of psuedanthia (false flowers) unique to the sunflower family (Asteraceae). At the edge of the capitulum, the conspicuous "petals" are actually ray florets - individual, bi-laterally symmetric, unisexual (female) flowers. The "petal" of a ray floret is actually a ligule - formed by the fusion of 3 petals. The remaining 2 petals are inconspicuous. At the centre of the capitulum is a cluster of disk florets - radially symmetric, bisexual flowers with 5 tiny petals fused into a corolla.
Below is a cross section of a capitulum. Immature disk florets in the centre appear submerged in a forest of white bristles.
These bristles are acutally the modified sepals of both types of floret. The sepals
of a flower/floret are collectively called a caylx. In the case of the
(many members of?) sunflower family the caylx has become a papus (pl. = pappi). Pappi aid in
wind dispersal of the seeds.
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| Cross section through a capitulum. |
The next 2 pics are of a ray floret. The papus (modified caylx) is obvious in the second picture. The two-lobed structure is the style (part of the female reproductive structures). Stamen (male reproductive structures) are absent.
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| Ray floret. The petal-like structure is a ligule made of 3 fused petals |
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| Ray floret. Papus is obvious from this angle |
Below are disk florets. The five lobes of the corolla are visible. In one of the florets (pictured alone to the right) you can see the style emerging from a theca - a sheath formed by the connate (fused together) stamina.
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| Crazy-pole near the end of flowering |
The crazy-pole commonly branches after flowering so by this time next year our resident one may start looking more candelabra-like.
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| First leaf appearing from the apex of a basal offshoot |
Lastly, here are a few pics of another sunflower relative that finished its first flowering a few weeks ago. Senecio pendulus (syn. Kleinia pendula), the inch-worm plant, is a scrambling succulent originally from Yemen and NE Africa. Senecio = "old man", after the grey-white hairs of the pappus. Colour of the florets notwithstanding the disk florets are similar to P. praecox. Notice the lack of ray florets. The inflorescence also differs, with capitula being borne singularly on loooooong peduncles (infloresence stalks).
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| A Capitulum of Sencecio pendulus |
Because of the compressed nature of a capitulum, the stalks of each
floret have been reduced to, well, practically nothing and their bracts,
that probably subtend each of those stalks in an ancestral species
prior to the evolution of capitula, have grouped to form an involucre
(pl. =involura ). To complete the resemblance of this false-flower
to a real one they take on the aspect of a caylx of sepals! As with the P. praecox, the actual
caylx of each individual floret has evolved into a pappus. The whitish,
waxy coating you can see on the involucre in the picture to the left is
one of a suite of adaptations to limit water loss (it also repels
water).
