where are you.. big city name ...

a blanket needs to trap rising warmth from the soil .. but if it is touching leaves.. the cold air will harm leaves touching the other side.. ergo.. it cant be touching leaves ...

if this happens year after year.. i might begin to question the alleged zone you claim to live in ...

one way to avoid all this is to get hardier versions of the plants you have.. if there are such ...

ken

ps: i bet its getting hard to find or replace xmas lights that actually generate heat ....

i see that forum was removed.. and bingo.. we now see answers ...

I'm outside Houston metro area, zone 9a. A low couple nights ago was 17F. Then 23-25F for two more nights.

I use old fashioned green string outdoor Xmas lights. This year I mostly placed them on/around the tropicals, and left the rest of the shrubs with just the frost cover blankets.

Frost cloth is from Dewitt, 2.5oz weight (supposed to add 8-10degrees), custom sewn to fit the plants, and weighted down at the bottom with the rocks.

If I were to create something that has air trapped between frost blanket layers, would bubble wrap be something I could use? Cardboard? Plastic trash bags? Thermal/foil material? So it would be frost cloth-mystery material-frost cloth sandwich.

Building structures to create air pocket for 2 freezing nights is not very practical. I would consider a custom/layered cloth covers thou. I have over 70 plants to cover, so there's a cost and storage factor to keep in mind. I have made trash bag "jackets" for the plants that I have used over frost cloth in the past when we were expecting rain/snow. I had better results with plastic bags+frost cloth on than this time around with just frost cloth. There was still some leaf burn, but only at the very top, not all the way throughout a plant.

The plants I have aren't supposed to be very finicky, except for a couple tropicals. I guess keeping them evergreen is a challenge when the temps dip into 20s. None of them died, just lost/burnt most of the leaves.

Thank you, all!

With regard to making air gaps with layers of material, it isn't that hard. Bubblewrap and cardboard will do nicely, but just layered sheets are a lot simpler. They will have few touch-points, and are mostly separated by air. Note that jackets that surround plants won't do the job. The strategy is to capture warm air rising from the soil. A jacket surrounding people keeps people warm because people generate heat, and the jacket holds it in. Plants don't generate heat. Lights of any kind under the sheets are good. You want a hundred watts or so under every square yard or two. That's easy to get with incandescents. Xmas lights are nice because the wattage is well distributed, and there little risk of burning things.

If you must cover and supply supplemental heat for landscape plants,you have the wrong plants and will lose them eventually despite your best efforts. Your time and expense can better binifit landscape if used elsewhere. There is an abundance of plants adapted to thrive in Houston without Winter protection. Let those that survive,survive unattended and replace those that don't survive with adapted plants.

Plants adapted to thrive in certain climates won't thrive if temperatures are abnormally low for that climate. It happens. It happened last week in central Texas. We had 12F. We're 8b, and plants adapted to our area are good to 20+F. So adaptation is meaningless if you get temperatures that are unusual. Happened two years ago as well. Well adapted plants were toast. So if you replace all your plants with well adapted plants, you may be in for a rare surprise.

Temps in the teens are very rare in zone 9, but plants adapted to zone 9, like gardenias and roses, will certainly be damaged by them.