Grevilleas for Cold Climates
Grevilleas have arguably become the most popular group of native plants cultivated in our gardens. Larger flowered species and hybrids such as Grevillea banksii, ‘Moonlight’, ‘Robyn Gordon’ and ‘Peaches and Cream’ are very widely planted and are in great demand. Unfortunately for gardeners in frosty climates these large flowered (sometimes referred to as ‘tropical’) grevilleas tend to suffer badly when the temperature drops below zero Celsius unless given plenty of protection.
The good news for cool climate gardeners is that there is a host of species and an ever increasing array of grevillea hybrids that are very frost hardy. Most of these species and hybrids belong to a group of grevilleas known as the spider flowered type, characterized by relatively small flower heads that are roughly spherical in shape. It is important, however, to point out that not every spider flowered grevillea is frost tolerant.
The epicentre for frost tolerant grevilleas is the mountainous country of southeastern Australia where a great diversity of species has evolved to survive frosts up to minus 100C, not to mention snow at the higher altitudes. These species often take many different forms in terms of flower colour and plant habit over their geographical range and many of the more interesting ones have been propagated by native plant enthusiasts and brought into cultivation. The juniper-leaf grevillea (G. juniperina) is a great example of this. This species varies from a prostrate ground cover to a decumbent shrub to 4 m in height with many different flower colour forms such as cream, yellow, orange to bright red. Many of these forms have been given cultivar names such a ‘Sulphurea’ (yellow), ‘Rubra’ (red) and ‘Pink Lady’.
Breeding cold tolerant grevilleas
As good as some of the wild species have proven to be for the garden there is now also an array of cold tolerant hybrid grevilleas available. Breeders such as Peter Ollerenshaw of Bywong Nursery near Canberra have created some wonderful hybrids that combine the best characteristics of two or more species. Many of these hybrids offer longer flowering periods on more compact plant habits that retain the outstanding cold tolerance of the parent species.
Growing cold tolerant grevilleas
- Before planting saturate the root ball by dunking the pot into a bucket of water
- If conditions are dry after planting supplementary watering may be needed until the roots are established in situ
- Tip prune before planting to ease transplant shock and create a more compact, floriferous specimen
- Use a low phosphorous native plant fertiliser in spring
- Prune lightly after each heavy flush of flowers
Grevillea ‘Lady O’
Grevillea ‘Lady ‘O’
Climate Frost hardy to at least -50C but also performs well in warmer climates including those with higher levels of humidity
Plant type A medium sized spreading shrub
Size 1-1.5m high by 2 m wide
Flower season All year in warmer climates, spring to autumn in colder areas
Comment This hybrid combines the vibrant red ever blooming flowers of G. rhyolitica with the frost hardiness of the elegant G. victoriae. The result is a compact plant that attracts birds to your garden all year round.
Grevillea ‘New Blood’
Grevillea ‘New Blood’
Climate Frost hardy to at least -50C but also performs well in warmer climates including those with higher levels of humidity
Plant type Groundcover
Size Up to 25cm tall with a spread of 1-1.5m
Flower season Autumn until spring
Comment The frost tolerant ground covering habit of G. juniperina has been combined with the long flowering habit of G. rhyolitica. This new hybrid is proving adaptable to a range of climates and soil types but a well drained situation will ensure success.
Grevillea ‘Fireworks’
Grevillea ‘Fireworks’
Climate Frost hardy to at least -50C and has proven to perform best in a cool temperate climate that is not too humid such as inland areas like Canberra as well as most parts of southern Australia.
Plant type Dwarf shrub
Size Approximately one metre in height and width
Flower season Flowers profusely from autumn to spring
Comment This hybrid of G. alpina is not recommended for humid climates such as coastal Sydney as it is somewhat susceptible to root rot. However, the spectacular bursts of red and yellow flowers make this a winner for colder, drier areas.
Royal Grevillea ‘Grevillea victoriae‘
Climate Most forms of this species will tolerate frosts below -50C. It prefers a cool temperate climate that is not too humid.
Plant type Dwarf to medium shrub
Size 1-3mx 1-2m
Flower season All year with peaks in autumn and spring
Comment The wild stronghold of this species is the snowgum woodlands of the Snowy Mountains, making this one of the most cold tolerant of all grevilleas. The olive green leaves have a silvery under surface that contrasts well with the red flowers.
Rosemary grevillea ‘Grevillea rosmarinifolia‘
Climate Most forms of this species will tolerate frosts below -50C. Tolerates dry conditions and can cope with moderate humidity levels
Plant type Dwarf to medium shrub
Size 0.3-3m in height by 1-3m in width
Flower season All year with a peak in spring
Comment This species has proven to be one of the toughest and most adaptable grevilleas for garden usage. Flower colour can vary from lemon-green to red to pink with cream highlights. Many forms of this species have been named as cultivars with some of the best including ‘Limelight’, ‘Pink Pixie’ and ‘Scarlet Sprite’.
Mountain grevillea ‘Grevillea alpina’
Climate Most forms of this species will tolerate frosts below -50C. It thrives in a cool temperate climate that is not too humid.
Plant type Dwarf to medium shrub
Size 0.2-2m in height and 0.5-2 m in width
Flower season Flowers sporadically all year with a peak in late winter to spring
Comment There are numerous forms of this species in cultivation with a tremendous range of flower colours including cream, green, pink, red , yellow with bicolour possible as well. It is quite sensitive to root rot and therefore does best in drier as well as colder climatic conditions.
Grevillea alpina in the wild
