Is it frost-hardy?


 Frost on parsley

As warm and sunny as our country can be, much of Australia is prone to regular frosts during the colder months, which means we can't just plant any old thing anywhere. Almost all of Australia falls into USDA cold zone 9a or above, and although that is not as severe as many other parts of the world, if you live in a frost-prone area it is worth checking the frost-hardiness of a plant before you buy. The good news is that there are many herbaceous perennials and bulbs that actually require an amount of chill hours to germinate, flower, and grow well. Here are some of our favourite plants that will happily overwinter without dying of cold in Australia:

Hollyhocks, delphiniums, and aquilegias are hardy to -40˚C.

Foxgloves are hardy to -35˚C.

Hellebores and Canterbury Bells are hardy to -28˚C.

Hydrangeas can withstand temperatures to -23˚C, although some bud damage can occur when the temperature drops below -6˚C.

Given that the coldest temperature ever recorded in Australia was -23˚C at Charlotte Pass, NSW, all of the above plants will survive the coldest of Australian winters. But watch out for unseasonal weather. Although it might not kill a plant outright, new buds and young leaf growth on even the toughest plants can be damaged during a sudden cold snap in spring. So if your delphiniums are popping up with new green leaves and you know a severe frost is coming, it is best to give the emerging plants some protection.

We also love growing different varieties of salvias. These plants come from all over the world, with varying degrees of hardiness. 

Salvia yangii (commonly known as Russian Sage, though actually native to Central Asia) is hardy to -40˚C.

Salvia nemorosa 'Ostfriesland', native to Europe, is hardy to -35˚C.

The native Mexican sages, Salvia leucantha (Mexican Bush Sage), Salvia uliginosa (Bog Sage), and Salvia microphylla 'Huntington Red' are hardy to -12˚C.

The South American native Salvia chamaedryoides 'Marine Blue' is hardy to -6˚C.

A hybrid of two species native to South Africa, Salvia 'African Sky' is hardy to -3˚C.

Salvia involucrata, and its cultivar 'Romantic Rose', will have its young shoots damaged by any frost at all. It is native to the tropical Caribbean coast of Mexico.

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