Photo by Melody

PlantFiles: Joshua Tree
Yucca brevifolia

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Family: Agavaceae (ah-gav-AY-see-ee) (Info)
Genus: Yucca (YUK-uh) (Info)
Species: brevifolia (brev-ee-FOH-lee-uh) (Info)

2 vendors have this plant for sale.

16 members have or want this plant for trade.

Category:
Trees
Cactus and Succulents

Height:
Unknown - Tell us

Spacing:
8-10 ft. (2.4-3 m)
10-12 ft. (3-3.6 m)
12-15 ft. (3.6-4.7 m)
15-20 ft. (4.7-6 m)

Hardiness:
USDA Zone 6a: to -23.3 C (-10 F)
USDA Zone 6b: to -20.5 C (-5 F)
USDA Zone 7a: to -17.7 C (0 F)
USDA Zone 7b: to -14.9 C (5 F)
USDA Zone 8a: to -12.2 C (10 F)
USDA Zone 8b: to -9.4 C (15 F)
USDA Zone 9a: to -6.6 C (20 F)
USDA Zone 9b: to -3.8 C (25 F)
USDA Zone 10a: to -1.1 C (30 F)
USDA Zone 10b: to 1.7 C (35 F)

Sun Exposure:
Full Sun

Danger:
Plant has spines or sharp edges; use extreme caution when handling

Bloom Color:
White/Near White

Bloom Time:
Late Winter/Early Spring

Foliage:
Evergreen

Other details:
Drought-tolerant; suitable for xeriscaping

Soil pH requirements:
6.1 to 6.5 (mildly acidic)
6.6 to 7.5 (neutral)
7.6 to 7.8 (mildly alkaline)

Patent Information:
Non-patented

Propagation Methods:
By dividing rhizomes, tubers, corms or bulbs (including offsets)
From seed; winter sow in vented containers, coldframe or unheated greenhouse
From seed; sow indoors before last frost

Seed Collecting:
Allow pods to dry on plant; break open to collect seeds

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There are a total of 72 photos.
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Profile:

3 positives
4 neutrals
No negatives

Gardeners' Notes:

RatingAuthorContent
Positive Kell On Feb 23, 2015, Kell from Northern California, CA (Zone 9b) wrote:

Per Jan Emming owner of the Destination:Forever Ranch and Gardens, a 40 acre desert botanical garden and sustainable living homestead in the Arizona desert with a nursery:

COMMENTARY ON MY PHOTOS;
1. http://davesgarden.com/guides/pf/showimage/386096/
Joshua tree flower clusters are about 18 inches / 45 cm long. They are scented with a musky, yet lemony, fragrance that appeals to the yucca moths they must attract to do the pollination required.

2. http://davesgarden.com/guides/pf/showimage/386097
Joshua trees flowering moderately in late February 2015, after no flowering at all in 2014.

3. http://davesgarden.com/guides/pf/showimage/386098
This close up of Joshua tree flowers shows the stamens arranged at the base of the pistil above the petals. At the tip of each stamen is a glob of sticky yellow pollen. The yucca moth females take this wad of pollen and purposefully pack it into a groove at the apex of the ridged, greenish pistil at the center of each flower. This completes the pollination of the flower, and the female then lays one or two eggs on the pistil. The developing larvae feed upon some, but never all, of the seeds of the growing pods. The fact that yucca pollen is too sticky to easily be transferred to the pistils by random accident and wandering insects other than the yucca moth means that the deliberate actions of the female moth are a critical link in the chain of reproduction for the species. By ensuring that the flowers get fertilized however, the female moth guarantees that her young will have the only food supply they can eat. This is one of the best examples of symbiosis, where each partner benefits from the arrangement of mutual interdependency.

4. http://davesgarden.com/guides/pf/showimage/386099
This scene and all of the others were taken on my 40-acre parcel at D:F Ranch. The narrow band of land where the Sonoran Desert and the Mojave Desert interface between Yucca, Wikieup, and Wickenburg AZ are the only places on earth where you can see saguaros and Joshua trees growing together naturally.

5. http://davesgarden.com/guides/pf/showimage/386100
Another scene of a wild Joshua tree and a saguaro growing only feet apart on my property near Yucca, Arizona. The town was named for the Joshua trees that grow in the vicinity.


GENERAL COMMENTS
After skipping virtually all flowering in the springtime of 2014, the Joshua trees (Yucca brevifolia) have decided to bloom again in 2015 (at Destination:Forever Ranch and Gardens, a 40 acre desert botanical garden/sustainable living homestead in Arizona), although not quite as abundantly as they did in 2013.

This cyclical flowering pattern, with good years interspersed with poor ones, appears to be a function of at least a couple of factors. One is that Joshua trees can only flower once out of a given "head", since the process eventually kills the terminal meristem as the cells do their final division from leaf and stem cells into reproductive ones.

This does not mean that the branch dies after flowering, just that new side-buds need to activate, grow for a few years, and then they too can rebloom. This feature is the one primarily responsible for ramification, aka new branch formation, in Joshua trees and other yuccas. If a given tree has three heads, and all of them flower one year, then it will be at minimum several more years before the new replacement branches are large enough to also bloom. But if each of the three heads that terminated is replaced by two side-shoots, then the plant may have 6 branches after flowering, which equates to greater reproductive potential. If trees bloomed heavily two or three years ago then it will simply be impossible for them to flower as much for awhile until new branches are big enough to do so.

Weather also plays an important role in how much the trees can bloom. Dry winters are obviously not conducive to much blooming, even if they are otherwise ready. The heavy bloom of 2013 followed by the dry winter and spring of 2014 resulted in a near-total absence of flowers last year. A winter of at least average precipitation, especially if it receives a cold snap sometime in December or January, appears to stimulate flowering as well. I assume that the several inches of snow this area received on New Year's Eve and Day helped spur the plants to flower, especially since they entirely skipped last year.

One more intriguing question is what happens to the yucca moths (Tegeticula sp) during years of poor or absent flowering? Yucca moths are the only insects capable of reliably pollinating the Joshua tree and other yuccas, and the moth requires the yucca plants in order to survive as well. Each species would soon become extinct without the other. But when you are a tiny white moth and your food supply is not present at all one year, how do you manage? What do you do for the entire year or more when yuccas are not blooming for one reason or another? How do the plants communicate to the moths, if in fact they do? Do they send pheromone signals to dormant moth pupae to emerge when they are flowering, and stay dormant if they are not? I have not seen any research into this important matter myself, but if anyone out there has I would be interested to find out more.

Regardless, this year (2015) is a decent one for Joshua tree flowers. Enjoy the pictures since it might be two more years before we get to see them again.

Neutral UtahTropics12 On May 5, 2013, UtahTropics12 from Orem, UT wrote:

This plant is so beautiful! And I see a lot of them here! They Are The palm trees Of northern Utah! They Grow great here!

Positive sag64 On Mar 7, 2011, sag64 from Salem, OR wrote:

I have a Joshua tree that I raised from seed that is about 14 years old. I keep it in a tall pot (3") as I live in western Oregon and am afraid it would be too wet if planted in the silty loam soil with a high water table in the wet season. I also keep it under the eave of the house on the east side so that it doesn't get a lot of rain falling into the pot. It is about 18" tall. It has damaged me and my wife with the sharp leaves many times!

Neutral baldrad On Jul 26, 2010, baldrad from Nampa, ID wrote:

Joshua Trees do great in Treasure Valley, Idaho (Boise area), 2500' elevation, high desert (10 or 11 inches precip.), variety of soils, so planting area must be prepared suitably. Hot summer days and evenings til midnite or so, several days in winter that may be connected or random down to zero or -5, but typical Dec or Jan night is 20 degrees or warmer, daytime 25-35. I'vd been here since '93; stories tell of some colder winters, but there are some Joshuas here 10' in height.

Trachycarpus takil (Kumayon (sp?) palm) has been tried here over the past 5 years (cold hardy to -5) but do poorly; the right index of factors apparently not here.

Neutral Kaelkitty On Jul 21, 2008, Kaelkitty from Adelaide
Australia (Zone 10a) wrote:

A synonym of this plant is Clistoyucca brevifolia (Engelm.) Rydb.

Positive peachespickett On Mar 8, 2008, peachespickett from Huntington, AR wrote:

Spent a lot of time with the Joshua Trees living outside Death Valley in Nevada for some years. Now I have one growing in one of my xeriscape beds here in Arkansas and it's actually surviving, wet and cold haven't bothered it, though it is planted in a 50/50 gravel/sand mix on a southwest wall. Grew from seed years ago, now about a foot tall. You can grow almost anything from the desert anywhere, provided it's hardy enough, you give it amazing drainage and plenty of sun. Also have sagebrush, pinyons, and a hundred other things that don't grow naturally within a thousand miles of here.

Neutral Matt33 On Mar 14, 2002, Matt33 wrote:

The Joshua tree is a large, erect, evergreen, arborescent monocot. It is usually single-stemmed, but trees with two or three stems will sometimes occur. The Joshua tree is the largest nonriparian plant of the Mojave desert, they can reach heights of 16 to 49 feet, and the trunks can grow 2 to 4 feet in diameter. Erratic branching will generally begin at 3 to 10 feet above the ground. Flowering of the Joshua tree requires a year with sufficient precipitation, if enough precipitation occurs they will generally begin to bloom in early spring with 18 inch clusters of 1.5 inch yellowish, bell-shaped flowers. This species grows from southern California, Mexico, and western Arizona eastward into southern Nevada and southwestern Utah.

Regional...

This plant has been said to grow in the following regions:

Phoenix, Arizona
Scottsdale, Arizona
Tucson, Arizona
Yucca, Arizona
Acton, California
El Cajon, California
Folsom, California
Mountain View Acres, California
San Diego, California
Twentynine Palms Base, California
Nampa, Idaho
Salineno, Texas
Magna, Utah
Orem, Utah



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