Hi Tony - I have never seen this growing here. I don't think it would be hardy in Denver- or elsewhere in Colorado. It tolerates Zone 7, but nothing close to the Zone 5 climate we have. Of course, maybe there is another cultivar that you are considering that is hardier! I'm certainly not an expert. I personally don't grow any Yucca because it is too painful to work around. :-D

Holly

Here is a link that might be useful: Yucca brevifolia - Joshua Tree Yucca

I'm growing Joshua tree here in Boulder. No damage after last winter, and is growing new leaves very quickly...it's about 6 inches tall and is starting to form a trunk. I would consider Denver/Boulder as Zone 6, not Zone 5. Just because we have hit cold temperatures in the past, doesn't mean that the temperatures are going to be that extreme every winter. I would try planting a Joshua tree in Denver; you might be suprised at the results!

There are also other trunk-forming yuccas that are more tolerant of cold. Check out HighCountryGardens.com and type "yucca" in the search field at the upper right of the screen. Yucca rostrata, Yucca faxoniana, Yucca brevifolia are some of the trunk-formers that are theoretically cold-hardy to Z5.

Nancy

I was just at Timberline Gardens on Sunday and I saw some of these. I was looking at other things and didn't notice if they were in pots for sale or if they were in the ground, but you might want to give them a call (ask for Kelly) and see what they can tell you.

Here is a link that might be useful: Timberline

Just checked his broadleaf evergreen list and he has both Yucca rostrata, Yucca faxoniana. Ouch on the price! But the ones I saw were BIG.

Yes, nrynes is right. Check out highcountrygardens.com, that's where I got most of my plants that are growing here. They grow under similar climate and conditions in Santa Fe, NM. Basically, if the plants can grow in Albuquerque and Santa Fe, they do have a chance and will grow in Denver and sorrounding areas because we somewhat have the same kind of climate.

I also am looking to purchase a hardy Joshua Tree, specifically Yucca brevifolia v. jaegeriana. I was going to purchase it from High Country Gardens, but it is not available right now. Does anyone know of any other sources for this plant that ship? I am definitely looking for a plant, not seed. Thanks very much! Leslie

I am aware of a Joshua Tree that is at least 9-10 feet tall with several branches located in the warmer side of zone 5. It is located at Willard Bay Gardens which is north of Ogden, Utah. I spoke with the owner and it has been outside for 18 years. I've also seen Joshua Trees in several locations in Salt Lake City (probably zone 6). I Have a 1 gallon pot size Joshua Tree I am growing and I live in zone 4. After several years of keeping it inside it's going outside. We'll see what happens.

Kevin

I've killed a couple of them here in Canon City. Killed a nice two-gallon size one that I brought up from Albuquerque. Also killed the little 'brevifolia v. jaegeriana' that I got from High Country Gardens, that's supposed to be hardy to zone 5.

Not sure what the problem has been. I've got a lot of different yuccas, so I know what they need generally, but if I do try another Joshua Tree it will be down to it's last strike, so to speak. Good luck.

Call for Kelly at timberline.. agreed. If it can be grown, he would know. Another person who would know is by the name Tom Peace. He experiments with things of this nature incessantly.. Kelly could probably get you in touch with him.

sorry to bump such an old thread...but the smaller joshua tree variety called yYucca brevifolia v. jaegeriana is very hardy in denver.
i know because i have one that won't stop growing.

Not sure if the Joshua Tree yucca would survive in Denver, although there a nice specimans in Salt Lake City, Reno, and even Boise. They typically need excellent drainage, up on at least 2 - 3 foot berms, and can survive and thrive in desert climates with temps much below zero. There are many large Joshua trees in the area of Caliente, NV, where the temps regularly go into the below zero range. And I personally have several growing here in the Boise area --- some for more than 20 years.

I have included a photo of a nice sized Joshua tree that has been growing in this particular yard for over 20 years. It was about 3 feet tall when planted.

Former Denver, Santa Fe, and Albuquerque resident here...

I've seen both typical Y. brevifolia var. brevifolia and Y. b. var. jaegeriana in the wild, and they both have colder and warmer ranges. I've used both in landscapes, and to me the main difference is the smaller v. jaegeriana is more sensitive to transplant and slower to establish.

Depends where one is located in huge Denver or other western cities and towns, as to which climate zone one is in. Not microclimate, but climate.

ABQ is a much different zone or two warmer than Santa Fe, even if one looks for a few exceptions. Santa Fe is milder than Denver (less cold, less hot, less up and down). Boise might compare to Santa Fe, but hotter and drier summers, wetter winters.

Consider the location on the continent, before using USDA. Then add latitude, growing season, and amounts of 32F, 90F, and other weather. Sunset's system is better for that. This is how Sunset compares with USDA (I might be wrong, and their maps might be) -

Denver = Sunset z 2b / USDA 5a-6a (semi-arid, great plains)

Santa Fe = z 3a / USDA 5b-6b (semi-arid, intermountain)

Boise = z 3b / USDA 6a-7a (arid, intermountain)

Abq = z 10 and spots of z 3b / USDA 7a-8a and spots of 6b (arid, intermountain)

Joshua Tree, both varieties, are native to Sunset z 3, 10, and 11 in the Mojave Desert - like the Chihuahuan, but drier and the "wet" season switched. In USDA terms, that's the intermountain arid parts of z 6a - 9a.

So, the plant source is probably as important a a healthy, rooted Joshua Tree..then planting in well-draining soil, gravel mulch, with other very xeric plants, and not over-watering.

Yes, I have over 20 planted in my yard in Southwest Denver

As for Denver I'm not sure but I have a friend in Leadville that has 3 of them growing in her back yard, in the winter months she just covers them with an insulated tarp. the smallest one is about 6' and the biggest about 8' all of them have good branches and they seem to be thriving up there.