I'm often taken aback by how wrong my preconceived notions of what destinations will be like compared to the real thing.
However with Joshua Tree, I found that my expectations were exactly what met me upon my arrival. It's a big desert full of Joshua trees. Although I might add that I was slightly disheartened when, after arriving in a large grove, I yelled out, "Hey Joshua". Not a single tree responded. Though in hindsight, maybe that was for the best because I'm not sure what my recourse would've been had one of them given a response.
Trying to describe Joshua trees by standard metrics and vocabulary is a hopeless task. So instead, I'll resort to the method I'm generally most comfortable with: ambiguous analogy and nonsensical rhetoric.
A Joshua tree is what occurs when a Pineapple grows up in a supportive and new age school that tells kids their dreams can come true. The teacher went around the room and asked each child what they'd like to be when they grows up. When it came time from the little pineapple, he exuberantly yelled, "A Tree!" And by golly, he did it.
Another? Ok, you asked for it...
A Joshua tree is what happens when the National Forestry Service asks Dr. Seuss to create a new park in the desert. But being the terrible procrastinator that he is, waits until the night before it's due and freaks out after realizing that he only has rocks, sticks, and a few pineapples for supplies. So he takes some hallucinogenic drugs and copy pastes the same thing over and over again across the desert and BOOM! Joshua Tree.