Editing Yucca brevifolia (section)

==Growth and development==
[[File:Joshua Tree Panicle 1.jpg|thumb|Flowers grow in [[panicle]]s]]

Joshua trees grow quickly for a desert species; new seedlings may grow at an average rate of {{convert|7.6|cm|in|1|abbr=on}} per year in their first 10 years, then only about {{convert|3.8|cm|in|1|abbr=on}} per year.<ref name="Keith 1982">{{cite journal | last1 = Keith | first1 = Sandra L | year = 1982 | title = A tree named Joshua | journal = American Forests | volume = 88 | issue = 7| pages = 40–42 }}</ref> The trunk consists of thousands of small [[fiber]]s and lacks annual [[growth ring]]s, making determining the tree's age difficult. This tree has a top-heavy branch system, and a broad root system, with roots in one case found {{convert|11|m|ft|0|abbr=on}} from the nearest Joshua tree.<ref name="Gucker 2006" /> If it survives the rigors of the desert, it can live for several hundred years. The tallest trees reach about {{convert|15|m|ft|0|abbr=on}}. New plants can grow from [[seed]], but in some populations, new stems grow from underground [[rhizome]]s that spread out around the parent tree.

The [[evergreen]] [[leaf|leaves]] are dark green, linear, bayonet-shaped, 15 to 35 cm long, and 7 to 15 mm broad at the base, tapering to a sharp point; they are borne in a dense spiral arrangement at the apex of the stems. The leaf margins are white and [[serrate]]d.

[[Flower]]s typically appear from February to late April, in [[panicle]]s 30 to 55 cm tall and 30 to 38 cm broad, the individual flowers erect, 4 to 7 cm tall, with six creamy white to green [[tepal]]s. The tepals are [[lanceolate]] and are fused to the middle. The fused [[pistil]]s are 3 cm tall, and the stigma cavity is surrounded by lobes. The semi-fleshy fruit that is produced is green-brown, elliptical, and contains many flat seeds. Joshua trees usually do not branch until after they bloom (though branching may also occur if the growing tip is destroyed by the yucca-boring [[weevil]]), and they do not bloom every year. Like most desert plants, their blooming depends on rainfall at the proper time. They also need a winter freeze before they bloom.

Once they bloom, the flowers are pollinated by the [[Tegeticula|yucca moth]] (''[[Tegeticula synthetica]]''), which spreads pollen while laying eggs inside the flower. The [[larva]]e feed on the seeds, but enough seeds remain to reproduce. The Joshua tree is also able to actively abort ovaries in which too many eggs have been produced.