Well you could add sugar... that would be good for your plants and prevent a freeze. However is a freeze going to be hard enough to do some damage? I could see it damaging what ever you had connecting your site-glass to the barrel but an open air barrel should be fine in a freeze.

I have to disagree that Y. filamentosa is good in all zones. I have problems with Y. filamentosa leaves (and someetimes the plants) surviving here in USDA zone 4a (-25ðF to -30ðF). In most winters the leaves that are not covered by snow are burned off and don't survive the winter. I have never had a Y. filamentosa flower in my yard. Or are you talking about Sunset zones? Sunset zones are entirely different from the USDA zones. I know many Californians use the Sunset zones since they're a little more precise than the USDA zones and cover a much smaller area than the USDA zones. USDA zone 1 is -50ðF or below. Very few plants can handle temps like that. Y. glauca I think is hardy to zone 3 and maybe into zone 2.

Have the seeds germinated yet? If you have actual plants, I have read that watering before the freeze helps with survival. The other question of course would be how cold is cold? Most of those plants have done very well for me with just a row cover (or nothing) even when it dipped to 20 last week. If the seeds have not germinated, I might consider holding off on the watering to keep them dormant just a little longer, but it could go either way.

Thank you so much for the links. The NRMCA link was a great summation of the research I have been doing. I obviously have no concrete experience but have done hours of reading in the last couple days. I am just butting heads with a sub who says that 40 years of experience tells him it should be OK because they are just footers - - even though no publication I can find supports this. The building inspector states that technically they have not violated a local code. Any advice on what I can do other than just document? Thank you!!