The Joshua Tree

It was about 7:30 one night in May of 2015. Eight hours earlier we had loaded up our car in San Francisco with tools, clothes, and our cats. We had just bought The Joshua Tree House a week earlier and were making our first trip to stay for a few weeks. We got off I-10 and on to highway 62 to start heading up the mountain to Joshua Tree, a drive we now know so well. The sky was starting to turn pastel pink highlighting the Joshua trees which appear to be straight out of a Dr. Seuss book. As we entered Joshua Tree for the first time as home owners, we were reminded by the sign to “Slow down and enjoy the view”. Pulling into our driveway for the first time just as the moon was rising over the mountains on the northern side Joshua Tree National Park. We sat down on the porch of our new home and took in the glowing moonlight over the Joshua trees.

We have since geeked out over learning all of the details about the plant itself. In honor of protecting the western Joshua tree (which is at high extinction risk with global warming), we’re sharing everything we’ve learned below. Let’s learn and protect these incredible plants!

What is a Joshua tree?

The Joshua tree or Yucca Brevifolia is the namesake tree of Joshua Tree National Park, and a symbol of the Mojave desert. They’ve been around since the Pleistocene era, which was about 2.5 million years ago! They’re currently only found growing in the United States southwest (California, Nevada, Utah and Arizona) which makes them incredibly rare and special.

While they were long considered to be part of the lily family, they are actually part of the agave family. Though they are called a ‘tree’ they are actually a plant—they are made of fibers and have no growth rings making it difficult to know their exact age. With a deep and extensive root system that can go as deep as 36′, they find a way to survive one of the driest climates in the U.S.

If you’ve spotted a Joshua tree before, you’d see a goofy looking plant with a 1′-3′ diameter trunk with thick green linear bayonet leaves that come to a sharp point. Until they’re around 3-9′ feet tall they are armless, but once they grow their arms their quirkiness comes to life. An incredibly important part of the ecosystem, about twenty-five birds use the Joshua tree as a nesting tree.

How tall is a Joshua tree?

On occasion we’ll spot a Joshua Tree around 40′ in height, though those are rare. The tallest one in Joshua Tree National Park is about 43′ high in Queen Valley forest (it’s called the Barber Pole, though we call it Graham named after our friend), and is estimated to be around 960 years old. If you’re driving through the park, you should be able to spot it easily as its right along the road. On older Joshua trees you’ll see extensive branching. The branches themselves can grow to 7-20 feet and fork at 2-3 feet.

Joshua trees need to bloom in order to grow new arms, so if you see a Joshua tree with no arms it means it has never bloomed.

Name Origins

The name is commonly attributed to Mormon settlers in the mid 1800s, though there is no direct evidence.
The story goes that the shape of the Joshua tree reminded the settlers of when the biblical figure Joshua reaches out his hands for a long period of time to guide Israelites. Joshua 8:18–26

Habitat

Joshua trees love high elevations between 2,000 ft to 6,000 ft in locations with cold winters (temperatures down to -13°F), hot summers (up to 120°F), and little precipitation (4 to 10.5 inches). They prefer dry soils on slopes, plains, and mesas.

There are two types of Joshua trees: the Western Joshua tree and the Eastern Joshua tree. The western Joshua tree is mostly in California and southern Nevada (they’re also up for protection) and the eastern Joshua tree is further east in California, Nevada, Arizona, and Utah. Each type is pollinated by different types of moths.

• California
  Mojave desert including Joshua Tree National Park. Mojave National Preserve is the largest concentration of Joshua trees.
• Arizona
  Beaver Dam Mountains (Utah border), Grapevine Mesa, Pearce Ferry, Joshua Tree Forest Parkway.
• Nevada
  Southern Nevada, Wee Thump Joshua Tree Wilderness.
• Utah
  Joshua Tree National Natural Landmark, Virgin River Gorge.

How Long do they Live For?

The average lifespan of a Joshua tree is 150 years, but they can potentially live up to a 1000 years! The grow very slowly and only grow about 3″ per year for the first 5-10 years, then 1.5″ every year after. It takes about 50-60 years for a Joshua tree to mature.

Height is a good way to estimate age for mature plants, but there’s no way to know exact ages as weather conditions play a factor in growth.

Approximate size to years:
1′ tall – 4 years
4′ tall – 20 years
8′ tall – 45 years
12′ tall – 70 years

Joshua tree Blooms

The Joshua trees typically bloom from February to April (though a couple years back there were some blooms in November due to some abnormally warm weather). The flowers are clusters of creamy whitish-green flowers, with bell-shape blooms with large seed pods.

Typically, a bloom encourages a new branch for the plant. Blooms are dependent on rainfall and the winter freeze, which means climate change could have a major impact on the plant. If the climate is too warm or dry through the winter the Joshua tree may not bloom and in turn new growth will be halted. According to Joshua Tree National Park, researchers believe that something about freezing temperatures stimulates flowering and in turn branching.

Yucca Moth

Tegeticula synthetica

We of course can’t talk about a Joshua tree without mentioning the Yucca Moth. Their symbiotic relationship is a special one. The Joshua tree depends on the Yucca moth to pollinate it, while the moth depends on the tree for a few seeds to lay eggs in the flower’s ovary. The moth ends up pollinating while laying eggs in the flower ovary, and when the larvae hatch within several days they feed on some of the seeds. Then, the leftover seeds are able to  grow into new Joshua trees.

The yucca moth is silvery, white and small in size with a body length of less than an inch, and an inch wingspan. They will hatch from cocoons in the spring time, and follow the scent of yuccas. Through the day, the Yucca Moth can be found resting and will pollinate at night once the blooms open.

Native American Uses

Cahuilla Native Americans referred to the tree as “hunuvat chiy’a” or “humwichawa;” and used leaves to make sandals, ropes, clothing and baskets. They also would harvest seeds and flower buds for meals, and used the reddish roots to make natural dye. The roots themselves are also rich in saponins and can be used as a soap.

Climate Change

Sadly, Joshua trees may virtually disappear from Joshua Tree National Park by 2070 due to climate change.
In the best case scenario, we will greatly reduce heat-trapping gasses in the atmosphere and 19% of the population will survive. If we take no action against climate change, it’s estimated that only 0.02% will survive.

As temperatures rise, Joshua trees are migrating to higher elevations in JTNP to find cooler weather and more moisture. While older trees use their water reserves to survive droughts, younger trees don’t have the reserves to withstand draughts. Climate change is unfortunately expected to bring more of this.

Rising temperatures, draughts, and carbon dioxide in the atmosphere which allows invasive grasses to grow all contribute to the desert susceptibility to fires. Only about 10% of Joshua trees survive fires, creating yet another challenge for the longevity of the Joshua tree.

Conservation

The Center for Biological Diversity petitioned the State in October 2019 to protect the western Joshua trees under the California Endangered Species Act. On August 19, 2020 the California Fish and Game Commission will decide whether to accept a recommendation from the California Department of Fish and Wildlife to grant the western Joshua tree protection under the California Endangered Species Act

How you can help protect the Western Joshua Tree

Words from the Mojave Desert Land Trust:

Let the commissioners know that you support the recommendations of the California Department of Fish and Wildlife and would like to see a YES vote for advancement to candidacy status under CESA.

Email: fgc@fgc.ca.gov

Talking points:

• This important species is under a barrage of threats, including climate change impacts, wildfire risk, and large-scale development projects. Four published studies have concluded that without intervention, climate change alone creates a high risk of losing western Joshua tree habitat almost entirely.
• The presence of the western Joshua tree benefits our economy. Its iconic presence attracts people to visit, live and work in the high desert. Its protection will encourage responsible development, preventing urban sprawl and overcrowding, increase property values, and preserve the rural quality of life which attracts people to our area.
• While some protection is provided by local ordinances, these are inadequate to respond to the multitude of threats that could lead to its disappearance. Not all Joshua trees are within National Park and National Monument boundaries. In fact, 40% of Joshua tree habitat is on private land, where it has only modest protection at best.
• We are at a critical juncture for the western Joshua tree. A collection of scientific studies predict the widespread decline of this iconic endemic species.
• Joshua trees don’t grow anywhere else on Earth. They attract visitors and new residents which, in turn, support our economy. In 2018, visitors to the National Park created an economic benefit of nearly $196 million both within the Park and its vicinity — that’s almost double the expenditure in 2014. For the local communities adjacent to the Park, 1,823 jobs were related to visitation.
• Attracted by the area’s scenic beauty and Joshua trees, the real estate market in the Joshua Tree region has steadily increased. New residents generally are not seeking a home in densely developed areas such as a subdivision, but instead are looking for a more rural lifestyle, ideally with proximity to the National Park, and Joshua trees are a very desirable feature.
• We recognize that the rapid growth of our communities and the dramatic increase in visitation at the National Park has resulted in its own issues such as traffic. These issues need to be addressed, but protection of the Joshua tree will help, not hurt our communities. Its listing will encourage local governments to develop a regional approach to conservation through a Natural Communities Conservation Plan. These plans focus on the conservation of large undeveloped areas, while encouraging new development on vacant land in already developed areas. This helps prevent sprawl and overdevelopment.

Sources:
Wikipedia
National Park System
National Wildlife Federation
Desert USA
Daily Press
Youtube
Joshua Tree NP on Facebook
Youtube
Ten Tree
US Forest Service
Wildflower
American Southwest
Mojave Project
USDA Plants
UC Riverside
MDLT on Medium