Welcome to a Canberra winter morning! This was our backyard yesterday morning – the temperature was a fresh –4*C! There was a nice coating of frost over the lawn, and the Sarracenia growing outside.
Here is a S. purpurea ssp. venosa from Triffid Park nicely frosted up. Note the thin layer of ice in the pitcher at bottom left and in the water tray. The Sphagnum and peat I use also freeze solid in smaller pots without harming the plants in any way; some northern hemisphere growers report pots being frozen solid for weeks on end with no harm caused to their plants.
Frost forms on items that are able to change temperature faster than surrounding items, including the air. For this reason, more frost develops on dried plant material – including dead Sarracenia pitchers – than on live plant material. Compare the amount of frost on the live S. leucophylla hybrid pitchers (above left) than the dead S. flava pitcher (above right).
Leaving some dead leaves on your Sarracenia collection can encourage light frosts to form preferentially on the dead leaves if there is a light frost. I personally don’t do this because I am rather fastidious with my collection’s hygiene, but others do with good results.
Stringing materials with lower specific heat around plants in your collection should also have the same effect – I thought frost decoys sounded like a nice name for such materials while researching how frost forms. Some lightweight cane fencing would likely work well as a frost decoy because it has essentially no thermal mass, but something darker would likely be even better, as it would radiate heat more efficiently. Even so, the use of frost decoys will only delay the formation of frost, not prevent it entirely. This means they will not allow you to grow Nepenthes under frosty conditions, for example. However, frost decoys would likely be helpful where frosts are not severe by distracting frost from forming on frost tolerant but sensitive plants like subtropical Drosera. Mulch works in much the same way, with the added benefit of providing insulation.