What ever you do don't use plastic and if you cover with cloth don't let it touch the plant. Maybe just an Umbrella over top will do the trick as the frost may settle on the top of the umbrella and not on the plant.
Can they take any frost at all? Some Agaves can in which case -1 is not a big deal.
Would a sprinkler going over night help like they do in Florida with the orange groves?
I hope someone else has an idea that will work for you.
most of my agave will do fine to five degrees, tonight is -3. the natives will be fine but A. americana, A. chrysantha, and A. victoria-reginae not so. I've got lamps on under tarps now, now my issue is the 15' Eucalyptus
I have never had a Eucalyptus that large but I can tell you that when the frost hits us up here they are hardy and I have them as seedlings/anuals in pots. They out do many other plants due to the oil in their leaves. Do they drop the leaves in your parts? If so I would think they can take some frost as they are an oily tree but I am only guessing. Lamps under tarps will help a lot and as long as the tarp is not touching the foliage you will be fine. I used seed heating mats last spring when we had a turn to the -O's and managed to save most of my babies in my greenhouse as that heat rising was all they needed.
Good luck I hope tomorrow you can tell me all is good!
Strung christmas lights along the trunk and a 200watt blub in the branches then wrapped it in a canvas tarp. E.microtheca is supposed to be evergreen to 5 degrees but froze to the main trunk last year at 3. we'll see how much good it did at -6 this morning.
Jesse, No joke when you think you may loose a precious plant or two!
That "freeze" thing we are used to and still we seem surprized when it arrives occasionaly too soon.
I too do funny things to try and prolong the life of some plant that is special. My neighbors laugh when theres stuff all over my yard and box's on containers when Hail is suspected or when I'm running around with plywood to lean against a fence to protect new babies from another of Mother Natures shows of force.
I do hope you made it through the night unscathed.
Bye the way I think we warmed up to 0 today after 20 days of colder than -20 C it feels like spring!
Jesse you are now in trouble cause she knows that more lights can go up!
I actualy like the winter as it gives a big change and the sky is so blue and the ground so white. I'm not a west coast grey sky person.
I use bubble wrap in my green house to make the space smaller for my seedlings in early spring. The bubble wrap is used like a wall not touching the plants and a timer turns on the heat mats for the night only.
It is getting lighter every day here and come june it will be light from 5 am till 11 pm and you can't beat daylight for plants. So I guess I cram all my growing in instead of spreading it out the whole year.