Joshua Tree NP - Joshua Trees in Bloom

The blooming cycle of the Joshua Tree is totally dependent on climatic conditions. Depending on the timing and intensity of winter rains, blossoming can occur any time from March to May, and can vary from very sparse to a rare abundance of blossoms in relative wet years. We were fortunate to be there in a good blooming year.

The flowers begin as greenish buds clustered near the end of the branches. The six tepals (3 petals and 3 similar sepals) then open up, to reveal a pod-like ovary, surrounded by six stamens, with one pistil. The flowers are waxy, white-to-greenish-white, and 2-3 inches long (5-7 cm). The flowers emit a sweet fragrance reminiscent of coconut.




PROPAGATION
The Joshua Tree pollen is so sticky that it cannot be carried by the wind. Pollination is accomplished only with the help of the tiny Yucca moth, with which this species has evolved a symbiotic relationship. This moth (Pronuba yuccasella) collects the pollen from a number of flowers and then chooses one flower as a home for its offspring. It deposits the pollen on the flower’s stigma in the process of laying eggs in the flower’s ovary. The newly hatched larvae will feed on the seeds (consuming only about 20 out of 200 in each ovary).

After the Joshua Tree flower is pollinated, the ovary swells with seeds and the flower falls away. The ripened fruit then falls to the ground where the seeds are scattered, often taken up by the wind. Very few will be able to germinate in the harsh desert conditions, but it is by this process of seed propagation that the new plant colonies are established. 

The Joshua Tree can also propagate by shoots from its roots or crown, and this is particularly important when the upper part of the tree is destroyed by fire.

Information for this post was taken from a variety of online sources: Flower Essence Society, Joshua Tree NP Info Page, Desert Tortoise Preserve Committee, Graeme Somerville: The Biogeography of The Joshua Tree (Yucca brevifolia).

Joshua Tree NP - Joshua Trees-1

Joshua Tree National Park is named for the abundance of Joshua Trees that grow there. This spectacular plant has become the symbol of the Mojave Desert. The name came from 19th century Mormon settlers: the uplifted branches of the trees reminded them of Joshua, the biblical Israelite leader, praying and pointing to the heavens.

There are two varieties of Joshua Trees. The ones we saw growing in the western and southern Mojave Desert are Yucca brevifolia herbetti. These are the largest trees, have relatively long leaves and branch only after they have flowered. (The other variety is Yucca brevifolia jaegeriana, which grows in the eastern Mojave Desert.)Joshua trees can grow from seed or from an underground rhizome of another Joshua tree. They are slow growers; new seedlings may reach a height of 10-20 cm in their first few years, then only grow about 10 cm per year thereafter. The trunk of a Joshua tree is made of thousands of small fibers and lacks annual growth rings, making it difficult to determine the tree's age. Because of their shallow root area and top-heavy branch system, Joshua trees are not very sturdy, but if they survive the rigors of the desert, they can grow as tall as 15 m and can live for two hundred years. One specimen in the park is about 12 m (40 feet) tall and is estimated to be 300 years old.
Serrano, Chemehuevi and Cahuilla Indians who have lived in the area for over four hundred years still identify the Joshua Tree as a valuable resource. Their elders call it “hunuvat chiy’a” or “humwichawa”. Their ancestors used the leaves of Y. brevifolia to weave sandals and baskets in addition to harvesting the seeds and flower buds for nutritious meals. In the nineteenth century, ranchers and miners arrived in the high desert concurrently with the Mormons. They hoped to raise cattle and mine gold. These homesteaders used the Joshua tree’s limbs and trunks for fencing and corrals. Miners used Joshua Trees as a source of fuel for the steam engines used in processing ore.
Information for this post was taken from a variety of online sources: nps.gov-Joshua Tree, Joshua Tree NP Info Page, Desert Tortoise Preserve Committee, Graeme Somerville: The Biogeography of The Joshua Tree (Yucca brevifolia).