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What is a Joshua Tree?

Joshua trees can be seen in the Mojave Desert in the United States.
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  • Written By: Megan W.
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  • Last Modified Date: 09 September 2014
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The Joshua tree, a distinctively American plant, grows only in the southwestern United States; it thrives in the arid soils of the Mojave Desert. The Yucca brevifolia, as it is scientifically known, is the largest member of its genus with a height between five and fifteen meters (16.4 feet and 49.2 feet). The Joshua tree has long, straight, dagger-shaped leaves that are about a centimeter (0.39 inches) wide at the base and taper to sharp points at the end. The leaves grow in a spiraling pattern at the ends of the stems; the dead leaves of previous seasons remain on the stem and build up below the new growth. When a winter freeze occurs and the amount of seasonal rainfall has been sufficient, these trees flower between February and April. Its off-white blossoms grow in clusters and give off an unpleasant odor.

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The Joshua tree reproduces in an exclusive and mutually beneficial arrangement with the female Yucca moth, whose organs are uniquely capable of gathering and transferring the tree’s pollen. The moth helps the tree reproduce while she completes her own reproductive cycle: she gathers the pollen when she lays eggs inside the ovary of a flower. As her eggs incubate, the tree’s seeds grow, and the moth’s larvae feed on the seeds when they hatch. The larvae usually leave enough seeds to grow more trees, but the Joshua tree has special capabilities to assure that the Yucca moth offspring don’t inadvertently overeat their welcome: if there are too many moth eggs in an ovary, the tree can abort it.

In addition to growing from seeds, the Joshua tree can grow from rhizomes of other trees. This type of growth helps the tree to survive floods and fires that kill the main tree but leave the root system unharmed. The tree grows rather slowly. In it's first few years, seedlings may gain two centimeters (0.79 inches) a year, but afterwards they generally grow only one centimeter a year (0.39 inches). The tree trunk is made of fibers and therefore doesn’t possess the growth rings that most other trees have. It also has a shallow root system that must support its disproportionately large and heavy size, which makes survival in the desert difficult. Despite this, a Joshua tree often lives to be several hundred years old.

Mormon settlers gave the Joshua tree its distinctive name when they were traveling westward toward their promised land. The shape of the tree’s outstretched branches reminded them of the Biblical story in which the prophet Joshua reaches his hands towards the sky. Joshua Tree National Park gives the tree another important place in American history: Franklin Roosevelt dedicated the park in 1936 to assure that California’s rapid urban sprawl wouldn't threaten the unique desert ecosystem in which the trees are king.

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anon158315
Post 5

The joshua tree has shallow roots because it does not rain often in the desert so when it does rain the tree can absorb the water fast.

anon143980
Post 4

what are the advantages to the joshua tree having shallow roots spreading out over a large area and having large, bulb-like roots deep in the soil?

LittleMan
Post 3

When I was growing up, my grandmother had a joshua tree in her back yard. She said that it represented triumph in the face of hardship, and would always get so excited when it blossomed.

To this day, I still keep a joshua tree poster on my wall, just to remember her -- although I have to say, I could never quite muster up the same excitement that she had when her tree flowered -- those things really do smell terrible!

EarlyForest
Post 2

I personally have never gotten the whole thing about joshua trees being inspiring. I mean, I think joshua tree photos look cool and everything, but the trees themselves just look kind of scraggly, if you know what I mean.

I do really like the area of Joshua Tree though -- I often travel through Joshua Tree for business, and I've always found the Joshua tree lodging and hotels to be very nice, for what it's worth. Just something you might want to bear in mind next time you're traveling out that way.

Charlie89
Post 1

I have always loved the symbolism of the Joshua tree, climbing up to the sky like it does. Although I wouldn't call them pretty per se, they do have a certain resilience and majesty that can really be very inspiring.

I guess that's why you see so many joshua tree posters and pictures -- people just can't get enough of these spare, yet fascinating trees.

I myself happen to live in an area with a lot of joshua trees around, and I always find it very peaceful and restful to take a walk around them and just take in their resilience. If you've never done it before, next time you see a joshua tree while camping or traveling, just take a few minutes and go and sit by it.

You'll see what I mean -- you'll come away refreshed and with a new sense of purpose. At least I always do.

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