Fifty-four 
THE SOUTH AUSTRALIAN NATURALIST 
June, 1953 
well established ornamental plantings | 
were damaged severely, most plants 
eventually recovered. 
Active shoot growth should be 
restrained as much as possible during 
the winter. This can be aided by with 
holding fertilizer and water in the 
autumn. However, in California, which I 
has a typical Mediterranean climate, the j 
autumn and winter rains when accom- < 
panied by periods of warm weather may j 
start growth in spite of such precautions. I 
Some colder regions with dry winters 
are known to be safer for certain plants 
than California. On the other hand, 
when freezing weather comes, it is some- 
times advantageous to have moist soil 
since this accumulates more heat. 
Many striking instances of the 
influence of ground radiation were 
observed in West Los Angeles during 
the freezes of 1947-48 and 1948-49. Since 
low temperatures in southern California 
are usually of short duration, ground 
radiation of heat is frequently an im- 
portant factor in mitigating the effects 
of low air temperatures. After prolonged 
low temperatures this reserve may 
become depleted, however. 
On the night of January 3-4, 1949 
(temp. 20° F.), plants under lath usually 
fared better than those fully exposed. 
In the West Los Angeles area, plants 
under overhanging eaves of houses or 
under trees often escaped serious injury 
only a short distance from locations 
where fully exposed plants were killed 
to the ground. 
Plants against masonry walls or 
stones were often much less injured 
than those against wooden walls. 
Although drying out of the soil is used 
as a means of conditioning plants against 
cold, the soil should be moist rather 
than dry in advance of the freeze, as the 
moist soil will store more heat. 
Trees. — The following records are of 
interest: — 
Agonis flexuosa severe injury 21 °F. 
Brachy chiton acerifolium slight injury 
25 °F. 
Brachychiton populneus no injur\ 
21 °F. 
Callistemon speciosus no injury 21 °F. 
Castanospermum australe no injury 
25 °F. and lower. 
Eugenia paniculata australis slight 
injury 24° F. 
Grevillea robusta no injury 21 °F. 
Hymenosporum fiavum no injury 21 °F. 
Lagunaria Pattersonii no injury 21 °F. 
Pittosporum. rhombifolium slight 
injury 26 °F. 
Pittosporum undulalum severe injurs 
21 °F. 
Stenocarpus sinuatus no injury 25°F. 
Some general recommendations are 
made at the end of this article. They 
are: — 
The following species should not be 
planted when cold temperatures are 
likely to be prolonged during the winter 
(or in low lying areas), Eucalyptus 
citriodora, E. ficifolia, E. Lehmanni, 
Eugenia paniculata , Melaleuca leuca 
dendon, Pittosporum undulalum, Tris- 
lania conferta and Harpullia pendula. 
Some trees likely to be destroyed 
when temperatures drop to 20°F. are 
Cupania anacardioides and Hymenu- 
sporum fiavum. 
Some trees which appear to be entirely 
safe at temperatures below 20°F. are 
Callistemon , Casuarina, Grevillea robusta, 
Hakea saligna, Lagunaria Pattersonii, 
Melaleuca genistifolia and Pittosporum 
phillyraeoides. 
Editor’s Note 
It would appear that this important 
field is untouched, for papers of a 
similar nature have not been noted in 
any Australian journals. Further obser- 
vations would be welcomed and members 
are asked to forward them to the 
Editor, giving details regarding species, 
degrees of cold endured and conditions 
prior to the frost. 
NATIONAL PARK 
HANDBOOK 
Advice has been received from 
the Commissioners of National 
Park that a new edition, com- 
pletely re-written of the Handbook 
lias been prepared. It is expected 
that this will be available in Aug- 
ust or September, and the cost will 
be 5/- per copy. Members wishing 
to secure copies should apply 
either to Secretary, National Park, 
Belair, or the Secretary of the 
Section. 
