cactus as a tree?

[Michael McKernan]

Joshua Tree is classified botanically in the family Asparagaceae (once,
Agavaceae, if I remember correctly), as Yucca brevifolia (short-leaved
yucca).  It is definitely not in the family Cactaceae, where botanists
classify most of the plants commonly referred to as "cactus."  Since it's a
monocot, what appears to be "trunk" and "branches" are probably composites
of leaf tissue, perhaps surrounding a pulpy interior.  If so, JTs would
probably fail the "woody" test for tree-hood, if there were one.  Saguaros
(and many other Cactaceae), OTOH, have internal wood-like frameworks, so
perhaps would woody-up if required by some wood pecker.  But this internal
framework is lattice-like, and quite different from the "solid" wood of a
typical "tree."

"Palm trees" are another case where the definition of "tree" may be
somewhat stretched.  Family Arecaceae (monocot angiosperms) includes
thousands of species, many of which are commonly known as "trees."
(Coconut palm tree, Cocos nucifera, for instance).

There are also a variety of plants known as "tree ferns," which are not
angiosperms (like most plants we think of as "trees"), and are classified
as members of the order Cyatheales.  These may have "tree-like stems up to
20 meters tall" (if you trust Wikipedia).  To at least some non-botanists,
various species have seemed enough like trees to elicit the common name.

I believe that botanists do not use the term "tree" as a technical term, so
you're barking up the wrong tree if you want to be botanically technical
about what "tree" means.

Joshua Trees are certainly the most tree-seeming Yucca spp. in North
America, as Saguaros (Cereus giganteus/Carnegiea gigantea) are the most
tree-like of the N.A. Cactaceae.  But for botanists, it's not an
interesting question whether or not either of these species fit "popular"
definitions of "tree," so they're just not going to go out on a limb about
this.

Michael McKernan
Benson, Arizona (just a few miles from the Saguaros of the Sonoran Desert).

On Sat, Mar 10, 2012 at 11:47 AM, Larry Sheldon <LarrySheldon at cox.net>wrote:

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> Sender:       American Dialect Society <ADS-L at LISTSERV.UGA.EDU>
> Poster:       Larry Sheldon <LarrySheldon at COX.NET>
> Organization: Maybe tomorrow
> Subject:      Re: cactus as a tree?
>
> -------------------------------------------------------------------------------
>
> On 3/10/2012 9:26 AM, Laurence Horn wrote:
>
> >> Look through these and tell me what you see.  Saguaro, Cholla,
> >> Joshua (Maybe not).
> >>
> > Hey, they call it a Joshua tree, not a Joshua "tree".  Of course, it
> > could be argued that despite its moniker a Joshua tree is no more a
> > tree than peanut butter is butter. And then there's phone sex.  But
> > still.
>
> My "Maybe not" indicated a question in my mind abort the Joshua Tree's
> status as a cactus--I'm not sure it is.  (And I see now that I'm not
> sure what a cactus is.)
>
> Bing says:  spiky desert plant: a spiny leafless plant with fleshy stems
> and branches and often with brilliantly colored flowers
>
> Joshua Trees have leaves.
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