A short list that varies depending on your definition of 'hardy' and trunking:

Hardy (no protection):
Yucca elata (some forms)
Yucca glauca (and var's)

Hardy (moisture protection):
Yucca elata
Yucca brevifolia
Yucca rostrata
Yucca thompsoniana

Others?

Can't speak for States side but Yucca Linearifolia performed better than Rostrata over here in the UK some plants taking -18C/ 0F without damage unprotected. An amazing plant and by far the most sought after here.They do have to be well rooted though.

Thank you. I have a yucca rostrata. I was thinking about just putting a plastic bag over it in the winter and maybe poking some holes in the side of the bag. Does anyone think this would work or would placing a bag over it kill it?

Be careful, some plastic bags are harmful to plants. I only use window cover plastic. It comes in rolls for winter sealing of windows.

Never use garbage bags, I have killed many plants before I knew this. 🙂

Woa! Thanks for telling me that! I've been nurturing this tiny rostrata for over 2 years now!

Hi cuja1, welcome aboard Palms North! 😀

Would love to see a photo of your Y.rostrata.
Any palms?

Blows me away that you're a 5b that far south of ... well.... Canada 😆 😆 😆 😯

Look forward to seeing how you protect it for winter.

Oh...did I say the "w" word already? 😐
(will put $1 in the curse jar).

Barb

Rostrata in 5b? I am having a terrible time here with my rostrata in 7a. Significant dieback each year, even though well planted, sized and sited. I wish you and your tiny rostrata luck in 5b. Don't leave it out there with only a bag over it.

I have to agree with that last post and I do have some experience with that. I live in a very solid zone 5. I planted a small rostrata from plant delight. It was planted in a very good microclimate up against south side of my house protected by an overhang. What happened was it stayed a permanent juvenile no bigger that the day I planted it. It lived for about 8 years but would completely die back to the ground every year than regrow to a little 6 inch tall plant in summer. It finally died 2 years ago. Maybe some straines or naturally accruing hybrids (with thompsonis perhaps) are hardier. They are also supposed to be a little more cold tolerant as larger plant. I think the main difference in a eastern zone 5 and western zone 5 (other than more moisture) is we may both hit -20, but we have a more constant cold. I suspect that's what will do them in. Maybe one of those min pop up greenhouses will do the trick because the temps will warm up quite a bit while the sun is shining so they will get a temporary break in the cold.

McKatelyn, agree with you 100%.
I also bought Y.rostrata sapphire skies from Plant Delights nursery and have them in a good south area under the overhang.
But they do need considerable winter protection.

Here are 3 of mine between the two in-progress winter protection for Washies.
<a href=" http://www.flickr.com/photos/southslope/6308802643/" title="DSC05069 by edible_plum, on Flickr"><img src=" " width="500" height="375" alt="DSC05069"></a>

The 3 y.rostrata initially had C-9 Christmas lights coiled at their base covered by a large sheet of clear plastic.
Then as it got colder, I inverted uninsulated garbage cans over the y.rostrata, with quite a bit of air place between that and the large sheet of clear plastic.
Lots of leaf-filled bags around each to keep the soil from getting too cold.

They made it but I was concerned they needed light in winter.
Very little damage by spring, so I was happy.

On mild days, yucca protection was opened up.

<a href=" http://www.flickr.com/photos/southslope/6792076099/" title="DSC05350 by edible_plum, on Flickr"><img src=" " width="500" height="375" alt="DSC05350"></a>

And thankfully the "protection mess" cannot be seen from the road 😆 😆 😳

Found the photo when I first received them from Plant Delights 4 years ago.
Cost a fortune with the phytosanitary cert, etc. 😆
<a href=" http://www.flickr.com/photos/southslope/2636882322/" title="DSC01429 by edible_plum, on Flickr"><img src=" " width="500" height="375" alt="DSC01429"></a>

Barb

Build a mound with good draining soil, use a small green house, make sure the air stays fresh inside, leave the zipper down a bit or open it on warm days, and I would bet it will live through a winter. On very cold days cover the green house with an old blanket. 😀

Here is a zone 5b winter pic. I had many uncovered yuccas that winter, and still do. 🙂

I have to agree with that last post and I do have some experience with that. I live in a very solid zone 5. I planted a small rostrata from plant delight. It was planted in a very good microclimate up against south side of my house protected by an overhang. What happened was it stayed a permanent juvenile no bigger that the day I planted it. It lived for about 8 years but would completely die back to the ground every year than regrow to a little 6 inch tall plant in summer. It finally died 2 years ago. Maybe some straines or naturally accruing hybrids (with thompsonis perhaps) are hardier. They are also supposed to be a little more cold tolerant as larger plant. I think the main difference in a eastern zone 5 and western zone 5 (other than more moisture) is we may both hit -20, but we have a more constant cold. I suspect that's what will do them in. Maybe one of those min pop up greenhouses will do the trick because the temps will warm up quite a bit while the sun is shining so they will get a temporary break in the cold.

A good observation there MCKATELYN. Rostrata is generally quoted as being hardy to -15C in its own habitat where temperatures can recover to above freezing but in cold dank Northern Europe and the UK the sun can be too weak. Last Winter's Siberian high caused havoc in Europe where many places remained below freezing for a long period of time. Luckily the UK escaped the worst. Without temperature recovery the freeze will penetrate further into the plant and kill off sap flow. The perma freeze in 2010 killed many Cordylines, Dicksonias and palms which had previously been use to freezes followed by temperature recovery 🙄

That's not what I expected from yucca rostratas. There's so much talk about them being hardy to zone 5b. They have pictures of them in New York. Mine's real small right now, my plan for this winter was to place a clear storage tub over it with lots of air holes drilled into it.

I'll try to get some pics soon!

Thanks for the welcoming Barb! I'm glad I found this site! I'm on Gardenweb but this seems to speak more to my obsession with exotic plants that may stand a chance where I live.

I was equally amazed that anywhere in Canada is warmer than here. That's one of the sucky things about living in the Midwest. Those darned Alberta clippers come down and make our temperatures plunge (no offense intended to Alberta)

Anyone know a good place to get zone 5b hardy yucca elata?

That's not what I expected from yucca rostratas. There's so much talk about them being hardy to zone 5b. They have pictures of them in New York. Mine's real small right now, my plan for this winter was to place a clear storage tub over it with lots of air holes drilled into it.

I'll try to get some pics soon!

I think that will work. Drill just enough for air movement, don't wont the heat to excape.

They are hardy to a zone 5b, but that depends how and where they are planted, and how big they are, and possibly where they seed came from. 😆

I have had small ones planted without cover in the pic above and they lived, still have them. 😉