June, 1953 
THE SOUTH AUSTRALIAN NATURALIST 
Fifty-three 
Hardiness of Australian Plants 
In the last issue of “Lasca Leaves”! 1 ) 
an extremely interesting and pertinent 
article appears by Vernon T. Stoute- 
meyer, “Cold Resistance of Suptropical 
Ornamentals.” While dealing with a 
wide range of garden plants it contains 
some interesting observations on the 
hardiness of Australian plants growing 
under Californian conditions. 
These observations were recorded 
during the winters of 1947-48, 1948-49, 
1949 -jO, in the vicinity of West Los 
Angeles. Temperatures ranged from 
above freezing point to the lowest, which 
was 24 °F. during the 1947-48 winter 
(20-21 °F. in low lying areas), whilst in 
1949-50 winter the ireeze occurred in 
early December following a period of 
warm weather with rain in November. 
Under these conditions growth had com- 
menced, therefore damage was severe. 
The following details are taken from 
the above mentioned paper. 
Eucalyptus. — Most of the Eucalyptus 
species commonly grown were not 
seriously affected by temperatures down 
to 20 °F. Eucalyptus pci folia lost much 
wood of the tops at this minimum in 
January 1949, but recovered well. 
E. cladocalyx (E. corynocalyx) was 
observed to be frosted noticeably at this 
temperature. Some injuries were 
observed on E. citriodora, E. Lehmanni 
and E. cinerea, although E. cinerea was 
untouched below 20° F. 
Acacias. — Except in the colder areas, 
all species of Acacias kept blooming or 
were undamaged during and following 
the January 3-4 freeze of 1949. Recorded 
damage only on A. podalyriae folia at 
approximately 20 °F. 
Ferns . — These were in an unheated 
lath-house where the temperature fell to 
20°F. The damage would have been con- 
siderably greater had the plants been 
in the open. 
Ferns showing severe injury or killed 
at 20°F. were Alsophila australis and 
Cyathea medullaris. Those showing 
slight injury were Platycerium alcicorne 
and Platycerium grande while those 
showing no injury were Adiantum 
altadena, Dicksonia antarctica and 
P ter is tremula 
( 3 ) Lasca Leaves — Quarterly journal of the 
Los Angeles State and Country Arborteum, 
Vol. II, No. 3 (July, '52). 
Vines. — Most of the evergreen and 
flowering vines were severely damaged 
or killed at temperatures between 30 U F. 
to 20 °F. 
Hardenbergia comptoniana no injury 
at 25 °F. 
Hibbertia volubilis slight injury at 
26 °F. 
Pandorea pandorana no injury at 21 °F. 
Sollya heterophylla no injury at 21 °F. 
Shrubs. — Observations indicate a par 
ticularly adverse influence of frost accom- 
panied by low dewpoints on tender sub- 
tropical and tropical plants. However, 
this may be a relatively unimportant 
factor with plants in other groups such 
as many of the Californian native plants 
or Mediterranean plants, particularly 
those having sclerophyllous or grey- 
tomentose foliage. This is an unworked 
field for ecological study. The use of 
controlled laboratory techniques would 
present considerable mechanical diffi- 
culties. 
The following Australian shrubs arc- 
reported upon: — 
Chamaelaucium uncinatum no injury 
at 21°F. 
Chorizema varium no injury at 24°F. 
Correa alba no injury at 21 °F. 
Correa speciosa lowest temperature 
resisted 18°F. 
Grevillea Banksii lowest temperature 
resisted 20°F. 
Kunzea sericea no injury at 25 °F. 
Leptospermum laevigatum no injury 
at 21 °F. 
Leptospermum scoparium no injury 
at 21 °F. 
The recovery of many plants injured 
by the 1948-49 freeze was often slow. 
In some instances, new growth did not 
appear until late in the following 
summer. The best recovery was made 
when plants were left unpruned and un- 
fertilized with minimum irrigation until 
new growth was well started. 
Freezing w r eather early in the autumn 
may be much more serious than the 
same temperatures would be later in the 
season. 
Materials recently planted in the 
ground or shifted to larger containers 
were especially vulnerable. All through 
the two most severe winters, losses of 
nursery plants were large, but although 
