The Frost Factor

The Frost FactorSpencer ShawIts that time of year when those of us who have planted trees over the past year, make our way to our tree planting’s after still and clear nights with a slight sense of dread as to what damage frost may have wreaked upon our young planting’s. Frost can be extremely destructive on a young tree planting if you are not aware of what plants can survive or even be immune to frost damage. Frost damage is at its worse when plants are frozen during the night and then thaw too quickly at sunrise. If nearby trees shade your planting’s first thing in the morning this can provide some frost protection, by allowing them to gently thaw. Even weed trees maybe worth retaining initially on a site for this reason.The key to surviving frosts is using species that are naturally frost resilient.   Using species that are frost hardy does limit your species selection initially but fortunately these plants are also generally very quick growing and within one or two years you may have developed an improved microclimate that allows you to establish many other plant species and add diversity to the site. Tree guards are often touted as the best way of protecting your trees from frost damage but the results seem to be very variable. The best success I have seen is a two-sided guard up slope of trees, the theory being that they cause the frost to flow around the trees rather than collecting on them. Only two sides being protected also exposes the young plant to less of a ‘softer environment’ and the resulting tougher growth means greater frost resistance. Various foliar sprays are also available that can assist with frost resistance such as Envy TM. But again they are not miracle cures and it comes back to species selection and choosing plants that can cope with the conditions existing on your site. Frost isn’t an unformidable barrier in the re-establishment of native vegetation but it does require some thought and planning. Lots of experimenting may be required yet to expand the diversity of planting’s in frost prone areas and improve their growth but if you stick with frost hardy species for the first few years of your revegetation you can’t go wrong. Talk to your local native plant nursery about frost hardy species. And don’t be left out in the cold when it comes time for your next planting.
Some Frost Hardy Species of the Mary River CatchmentSPECIES NAME      COMMON NAMEAcacia sp. Wattle’sAllocasuarina sp. She Oak’sAraucaria sp. Bunya or Hoop PineCallicoma serratifolia White AlderCallistemon sp. BottlebrushesCasuarina cunninghamiana River She OakEucalypt sp. Gum’sGrevillea robusta Silky OakHymenosporum flavum Native FrangipaniMelia azederach White Cedar