|
There are 20,000 vascular plant species in
Australia, the majority found nowhere else in
the world. The Protea (genera Banksia,
Dryandra,
Grevillea,
Hakea,
Isopogon,
Telopea)
and Myrtle families (genera Callistemon,
Eucalyptus,
Kunzea,
Melaleuca,
Leptospermum,
Xanthostemon)
are found chiefly in the southern hemisphere
and trace their history back to the supercontinent
Gondwana. These plants require adequate light,
even root temperature, air movement, good drainage,
and, for many, a Mediterranean rather than a
humid, tropical environment. I grow these plants
in containers that are kept in a well-ventilated
sunroom under full spectrum fluorescent lamps during the winter and outdoors in the
summer. Growing these plants in the Washington,
DC area is a real challenge because they do
not like the hot, humid summers and cold, frosty
winters. This climate is quite different from
the flora-diverse
area of southwestern Australia where summers
are long, hot, and dry and winters are cool
and moist. Most Australian plants can only tolerate
a period indoors from a few days to a few weeks
(Blombery
1983; Elliot
1988) and eventually need to be put outside
(Ratcliffe
and Ratcliffe 1987). I lost 18 plants in
just 3 days in September 2001. Too low humidity
and the leaves become dry and brown around the
edges. Too much water and high humidity promotes
mold, root rot, leaf spots and blotches, and
insect larvae. Older leaves develop powdery
mildew and drop off when the soil is too damp
or humidity is too high. The soil fungus Phytophthora
cinnamomi can kill large numbers of plants
rapidly. Soils for Proteaceae should be well-drained,
acidic (pH less than 6.5), and low in nutrients,
especially phosphate and calcium (Matthews
1993). Banksias particularly western Australian
species, Anigozanthos (Kangaroo Paw), and others
don't like 'wet feet' and high humidity. Many
Callistemons tolerate even poorly drained soils.
The growing
medium that I use is a mixture of pine bark, perlite, and Pro-Mix® BX. Although the soil is free
draining, these plants still require adequate
moisture. Inexpensive moisture and pH meters
routinely monitor the moisture at the base of
the container and the acidity. Elemental sulfur
or iron sulfate can lower soil pH. Most Australian
plants have adapted to low-phosphorus (P) soils
so avoid high-P fertilizer. Every 2 weeks, I
apply fish
emulsion (5-1-1). Yellow leaves with green
veins may indicate an iron deficiency, so iron
chelate should be periodically applied to the
soil.
|
