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Site preparation - frost protection
Site preparation - Protection from frost
Frost is a significant cause of tree death or damage in some parts of Australia. Frost is more prevalent at higher altitudes, but can occur almost anywhere in southern and inland Australia. There are parts of the landscape where frost will be more severe than in others. In low depressions or areas with a very low slope cold air cannot freely drain away and so accumulates overnight. Frost is less prevalent on sloping sites or where there is free movement of air.
Plants naturally harden if the severity and onset of frost is gradual, but most damage occurs from early or late frosts when plants are not hardened. A -2 degree frost can do more damage in May than a -7 degree frost in July.
There are several strategies for overcoming frost:
- Species selection - get the right species for the site,
- Provenance selection - collect seed from the same altitude and topographic position (populations in frost hollows are much more tolerant than those on slopes),
- Timing - plant frost sensitive species as early in the season as possible and encourage rapid vigorous growth,
- Hardening - no supplementary watering or fertiliser in Autumn (discourages soft new growth prior to winter) and harden plants after they leave nursery conditions for a few weeks prior to planting,
- Exception to above is to use a foliar spray of a Potassium fertiliser in Autumn as this hardens leaves. There are commercial K fertilisers available.
- Use tree guards when planting in autumn or late summer in very frost prone areas (only useful to protect basal stems from splitting or to protect leaves within tree guards and only confer about 20 of protection)
- Use anti-transpirant polymer as foliar spray or dip when planting - this gives about 6 weeks of protection, 2-30 only.
- Useful for early spring or autumn plantings where you get a sudden frost.
- Don't mulch in winter as it stops the ground warming up.
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