You can easily do an internet search to give you an idea about hardiness, Plant Delights Nursery has many agaves along with temp limits, but there's nothing better than some good old experimentation. I am in Zone 7, we haven't had anything lower than about 8F for many years, I have ovatifolia, americana, and parryi truncata that have survived in pots, they are kept completely dry underneath an awning during the cold months.

If your budget allows it, I say go for it, many should survive nicely, although you may want to grow them in pots that are plunged underground in case a severe cold spell comes, you can retrieve some plants into safety, even though it won't be easy digging through frozen soil. And try to choose clumping varieties, the babies can be plucked and saved in case the parent plants don't make it.

The cold frame idea seems OK, but what will you do if/ when the plants get large? I also question the ventilation, it might get quite warm on a sunny day, but in reality it shouldn't harm agaves that are outdoors all year.

How big of a cold frame were you planning?

hi xerophyte, and thanks for the detailed reply.

I've looked at the information from plant delights nursery as well as yucca do nursery to guide my agave selection for the more hardy varieties. I actually composed my list based on their information as well as google searches. Since most of the ones they list are still rated zone 7, I decided to ask and see if anyone has experience growing them in colder zones(hence this post).

My cold frame idea will be rather large, about 4 or 5 feet tall in the back, sloping to a 1 to 2 foot height in the front. I have a series of sliding glass doors that I picked up last summer and was thinking about making the cold frame out of them (i.e. wood on all four sides and glass on top). The reason for ventilation would be to reduce humidity inside the cold frame during the winter months. I plan on completely removing the glass covering during the summer. My current budget will only allow me to choose two or possibly three from the list I posted, which is why I was interested in hearing other people's experiences with those species/cultivars. Any other tips? Thanks!

I live in West Arkansas. We had 29+ inches of rain in two months of winter with a mild ice storm, snow, freezing rain, and 12 degree lows. I have a young agave havardiana and several of the utahensis and its subspecies(eborispina, nevadensis) and toumeyana and they all were unfazed by winter even though they were planted right before the rains started. All are planted in 50/50 gravel-sand mix in a raised west-facing bed and were not even affected by the late freeze. havardiana seems particularly tough. I get my cacti and agave from either high country gardens or e-bay. Good luck!

Hi tree_guy. I have some spare agave lophantha. They are growing in raised beds with no covers. Have survived 10 F without loss. Can trade please advise. Thanks Doc

Another simple alternative, at least before the plants get too large, might be to cover your plants with a plastic garbage can or other large container, and place a brick or rocks on top to prevent tipping over from wind.

When it is cold, the agaves are dormant, so they do not need light, and the can would prevent precipitation.

Thanks all for the input. The garbage can idea sounds interesting and significantly less labor intensive. I might try that instead.

saquaroa, Thanks for the offer, but I don't think it would survive for me. 10F would be pretty mild for my area during the end of winter. Early winter usually stays above 0F, ranging from single digits to just below freezing. Late winter gets a bit colder, our temps usually stay between -10F and about 10F during all of January and most of February.

Well, I decided to go with Agave gentryi jaws, Agave parryi ssp. truncata, and Agave montana baccarat. I'll let y'all know how they fare next spring!

Hey, it is spring again! tree guy, how did the agaves do over the winter?
If all went well then I might try to get a hold of the steel blue type of agave americana.
I am in a marginal zone between 6b and 7a, with relatively dry winters and quick draining sandy soil. Do you think that I would be able to keep the plant alive with minimal protection?

Hi koicool1,
Thanks for reminding me of my post here! Spring isn't quite here yet in my area, we just got 4 inches of snow the other day! However, I peeked in through my covering, and everything seems to have survived. I'll only know for sure once growth begins again in a few weeks(end of April to early May). Because of Lake Erie, we get spring pretty late here in Buffalo.

Here's what I ended up doing:
I made a raised bed out of cinder blocks. I tilled up the existing soil and mixed in bags of paver sand and paver base(chunks of gravel) resulting in really well drained soil. I planted the following species, which then had most of the summer to establish themselves:
Yucca brevifolia v. jaegeriana
Yucca faxoniana
Yucca rostrata
Echinocactus texensis
Echinocereus fendleri v. kuenzleri
Echinocereus triglochidiatus 'White Sands Strain'
Echinocereus reichenbachii v. Baileyii
Agave gentryi jaws
Agave havardiana
Agave parryi
Agave parryi ssp. truncata
Agave montana baccarat
Agave utahensis
For the winter I covered the raised bed with large glass panes like I previously mentioned. However, those began to leak, so I put a layer of heavy duty transparent plastic over top of it. I'll remove the plastic and glass covering once the chance of frost has passed (late April).

If you are between zone 6b and 7a with dry winters and quick draining sandy soil, I'd deffinately give some Agave's a try. If I remember, I'll post again once I know for sure which of my guys made it and which didn't, but that won't be for a few weeks.

The verdict is in, here's what made it and what didn't make it for me this past winter.

These species came through pretty much unscathed:
Yucca faxoniana
Echinocereus fendleri v. kuenzleri
Echinocereus triglochidiatus 'White Sands Strain'
Echinocereus reichenbachii v. Baileyii
Agave havardiana
Agave parryi
Agave parryi ssp. truncata
Agave montana baccarat
Agave utahensis

My Yucca rostrata and Yucca brevifolia v. jaegeriana were eaten by rodents.
The Agave parryi ssp. truncata lost its outermost leaves but is otherwise in perfect condition.
The Agave gentryi jaws was outright killed.