The Joshua tree (Yucca brevifolia) is an iconic, slow-growing, evergreen synonymous with the Mojave Desert in the southwestern United States. The largest of all the Yucca species, they can grow to over 30 feet.
When these long-lived plants mature, they develop distinctive extensive branching with rounded, open crowns (usually when they reach between 3 and 9 feet in height). The foliage develops in rosettes on the tips of the branches. However, young trees grown in a garden setting will usually lack branches and have bent backwards leaves.
The creamy-white, small flowers that cluster at the ends of long panicles develop into light green seedpods. This species provides an important food source and shelter for birds and small mammals in its harsh native environment.
These trees are only suitable for growing in areas with similar conditions to their dry, desert native habitat. They are sometimes grown in desert gardens, xeriscape landscapes, and rock gardens. As a specimen plant, their unusual, architectural shape makes a bold focal statement.
Joshua trees can be hard to find, and purchasing from a reputable supplier is important to ensure the trees or seeds are not from protected, wild populations. It's best to plant these trees from November to March—they don't have a good recovery rate if you transplant them when the weather heats up.
|Common Name||Joshua Tree, Yucca Palm, Tree Yucca, Palm Tree Yucca|
|Botanical Name||Yucca brevifolia|
|Plant Type||Woody Perennial, Evergreen, Tree-like|
|Mature Size||15-30 ft. tall|
|Sun Exposure||Full Sun|
|Soil Type||Sandy, Loamy, Well-Drained|
|Soil pH||Acidic, Neutral, Alkaline|
|Hardiness Zones||6-10, USA|
|Native Area||Southwestern USA|
Joshua Tree (Yucca Brevifolia) Care
A highly cultivated garden environment isn't going to be right for growing a Joshua tree. They thrive in poor soils and where summers are long, hot, and arid, and there's a significant drop in temperatures come winter. Your tree won't survive in a region with high humidity and rainfall.
The rhizomatic root system of these trees is deep and vast. They need plenty of space to grow—keep them away from the home foundation and any pipes or utilities. Think carefully about the position as Joshua trees don't transplant well.
As you would expect of a tree native to the desert, it needs a full sun position to thrive.
Joshua trees can grow in sandy, loamy, rocky, and clay soils, but they must be well-drained and dry. Unlike many plants, the poorer the quality of soil, the better they are likely to grow. Fertile, rich soil is not the Joshua tree's friend.
This is a highly drought-tolerant tree. Established Joshua trees only need supplemental watering in periods of drought. When the ground is dry, dusty, and crumbly to the touch, you can water until the soil is saturated. Don't water it again until it fully dries out, at a maximum of once per month during the growing season. Overwatering can lead to root rot.
Temperature and Humidity
For your Joshua tree to survive, the climate should replicate the extreme, elevated Mojave Desert as closely as possible. It needs a scorching hot, dry summer and a cold winter. Without a dormant period, the tree will die, so these changes in temperatures are important. They can tolerate winters as cold as 12 degrees Fahrenheit and summers as hot as 120 degrees Fahrenheit. It's certainly not a tree for growing in the tropical, humid southern regions or in areas with high volumes of rainfall.
Wild Joshua trees thrive in poor, infertile soils, so they shouldn't need supplemental feeding. Fertilizing may encourage faster growth, but this can alter the naturally appealing form of the tree.
If you want to use fertilizer, select a slow-release type suitable for desert plants or a mild, slightly acidic organic option like a fish emulsion. It won't need regular feeding—an annual dose or one in late spring and early fall is sufficient.
Types of Joshua Tree
This is not a highly cultivated species, but if you're looking for a compact version of the tree for a smaller landscape, you can opt for Yucca brevifolia var. jaegeriana. This dwarf tree version typically grows to around 10 feet and has shorter branches than the standard Yucca brevifolia.
Part of the appeal of the Joshua tree is its distinctive natural form—it won't need any pruning other than to remove any old, damaged flowering stems. By leaving the branches with dry leaves, they can insulate the plant in cold winters by absorbing moisture.
How to Grow Joshua Tree From Seed
Growing Yucca brevifolia from seed is tricky but not impossible. The flowers can only be pollinated by a species of moth native to the trees natural habitat, so hand-pollination using the likes of a small paintbrush is often necessary. For best results, you should sow fully ripe and fresh seeds.
- Seeds are usually ready to harvest in late summer. The seed pods should be dry with black rather than tan seeds inside and not fully split open.
- Once you have collected the black seeds, check them over to make sure they don't have any holes in them. This will only be a problem in native areas where the moth larvae may eat the seeds.
- Use a shallow tray with a moist paper towel on it and place the seeds on this and then cover them with another moist paper towel.
- Keep the tray at room temperature and moisten the paper towels whenever they start to dry out. Make sure, however, that the seeds are not sitting in water.
- After around 10 days, there should be stems starting to sprout from the seed end.
- Once these shoots appear, they can be moved into a fresh potting mix and kept in a greenhouse. Because the seedlings won't appreciate being disturbed while establishing, select a large container rather than a small pot, so you don't need to transplant them for at least the first two winters.
- Make sure the white sprouting stems are facing up when you pot them.
Potting and Repotting
Joshua trees are slow-growing, but they do have an extensive root system. If they are being grown in a container, you should repot them in a larger pot every few years at the end of winter. Because they don't like being transplanted, you need to do this very carefully.
How to Get Yucca Brevifolia to Bloom
When a Joshua tree is in flower in spring, it produces densely clustered panicles that can be up to 20 inches long. The small, individual, white-green flowers are oval-shaped and have an unpleasant, mushroom-like fragrance. Not every tree flowers annually. There needs to be perfect weather conditions to facilitate flowering, and not every tree will bloom annually. Freezing winter conditions stimulate the following season's flowers. Too little or too much rainfall can also impact blooming success rates.
How long can Joshua Trees live?
These are long-lived trees. Experts estimate one tree in California to be around 1,000 years old. Typically, they take about 50 years to fully mature and live around 150 years.
Are Joshua trees easy to grow?
This species is incredibly low maintenance, but only if it gets the very specific desert conditions it needs to thrive. It hardly needs watering, won't need fertilizing, and you won't need to prune it. A bit of neglect rather than being too attentive is what the Joshua tree favors.
Can Joshua trees grow indoors?
Because these trees need cold winter conditions and hot and dry summer weather, they aren't likely to flourish indoors. This is definitely a tree best kept outside.