King Palm - curled leaflets vs flat... Why?

[BayAndroid]

So this happens with all of the king palms I've tried and I'm not sure what the reason for it is... 

The below pictures are from the same Archontophoenix Cunninghamiana. An older frond has flat leaflets, whereas the new ones have more curled leaflets... The result is a pointy narrow leaflet, vs a more full and lush looking one. 

 

Anyone know what causes this? 

[James B]

Sun. King Palms natural environment in under canopy of older palms and taller Eucalyptus trees. 
 

Cunninghamiana seems to be the least sun tolerant(at least inland) especially the Illawarra type in my yard just looks terrible in full sun. The leaflets are curled and have an atrophied look and no matter how much I water seem to have much thinner trunks than the standard King especially the ones in afternoon shade. 

[BayAndroid]

Thank you, that clears up a lot. I just got some Purpurea and a Teracarpa tripple to add to my collection, I suppose those won't have the same issue?

[James B]

Purpurea in sun can do the same thing. Teracarpa is basically a Maxima type and will do better in full sun. You’ll see some curling on the last few leaflets at the end of the leaf. Overall the Alexandrae/Maxima complex I’ve found take sun better than Cunninghamiana.

[Tyrone]

All Archontophoenix are rainforest dwellers in nature. It's a sun issue I reckon.