What is (and is not) a Palm Tree?

I love palm trees and lush green foliage. Both evoke images of tropical islands, sun and sand, desperately needed right now in the coldest part of the Canadian winter. So last week, I decided to post some palm trees from my 9 month Australian trip, but part way through uploading the photos I realized they weren't all palm trees... and that needed sorting out...

What is a palm tree?

And here I found myself back in my high school biology class studying taxonomy. Well, not quite. New findings and the ability to check DNA have updated what I studied, moved entire branches, and changed names. It's not like it was static before but it's changing faster, and all along there were competing classification systems of which I was blissfully unaware.

In taxonomy, palms are in Kingdom: Plantae (plants)->Phylum: Magnoliophyta or Angiospermae (flowering plants)->Class: Liliopsida (Monocotyledons)->Order: Arecales->Family: Arecaceae (palmae) and we can stop there at the palm family.

There are over 2,600 species of palms and they are not all trees since the rattan species climb like lianas and others are more like shrubs. Palm trees are known for their branchless stems, more closely related to bamboos and grasses, and unlike real trees, there is no secondary growth i.e. no outward growth creating annual tree rings. There is no bark.

Their fronds are of two basic types; pinnate (feather-like) or palmate (fan-like). The coconut palm in the first photo is pinnate. The one, above, is palmate.

The Assyrians believed that a palm tree growing beside a stream was the symbol of eternal life. The palm was certainly their most valued tree and palms are of significant economic importance today, typically related to the fruit they bear.

This is not a palm tree. It's a cycad.

Cycadophyta, Cycads for short. Kingdom: Plantae (plants)->Clade: Tracheophytes->Division: Cycadophyta->Class: Cycadopsida. Although superficially resembling palms or ferns, they are not closely related to either and they bear cones. It doesn't help when the plants in this photo, above, are called Sago palms.

This is not a palm. It's a Ravenala.

It's common name of Traveler's palm is not helpful. Kingdom: Plantae (plants)->Clade: Tracheophytes->Clade: Angiosperms->Clade: Monocots->Clade: Commelinids->Order: Zingiberales->Family: Strelitziaceae->Genus: Ravenala.

This is not a palm tree. It's a Dracaena.

It helped to learn that palms don't have branches or bark so I was already wondering what it was. They call this a dragon tree. Kingdom: Plantae (plants)->Clade: Tracheophytes->Clade: Angiosperms->Monocots->Order: Asparagales->Family: Asparagaceae->Subfamily: Nolinoidea->Genus: Dracaena. (Thanks @nikv.)

Correct me if I'm wrong, but I think this might be a Dracaena too, although a difference species. Perhaps it's the one called a Dragon's blood tree.

This is not a palm. It's a Grasstree.

Grasstrees are unique to Australia, probably worth a post of their own. Family: Xanthorrhoeaceae->Genus: Xanthorrhoea->Species: Glauca.

Just a couple of palms (real ones) lining the Sydney waterfront.

Images

Photos taken with my Canon SX620 HS in Hawaii and Australia.

@kansuze