108 
KATHY M. NICHOLS, J. H. BROWNE AND R. F. PARSONS 
short-lived in cultivation (Jones & Gray 1988), 
one of us (JHB) has observed individual plants 
of both species at Red Cliffs for more than 20 
years. There has been no apparent size increase. 
It is possible that such plants may be very long- 
lived like those of other clonal species (Janzen 
1975). 
Discussion 
Our observations suggest that some shoot 
growth occurred throughout the February- 
August period but that this was slow at the start 
and the finish, presumably due to low soil moist¬ 
ure and low temperatures respectively. Presu¬ 
mably shoot growth stops completely in very dry 
conditions like November-December 1990. 
Shoot growth is clearly much more vigorous in 
summer after thunderstorms or general rain 
than at other times. 
In colder areas of southern Australia, intro¬ 
duced species of Asclepias are said to “die back 
when (night) temperatures drop below 0°C” and 
so to “disappear over winter” (Zalucki 1986). In 
our 1990 work, Marsdenia and Rhyncharrhena 
did not show any frost damage in a winter when 
the lowest absolute minimum screen tempera¬ 
ture at Mildura was — 1°C. Both are said to be 
tolerant of light to moderate frosts (Jones & 
Gray 1988). However, for Marsdenia , “foliage 
may dry off after frosts” (Griffin 1985), and in 
the winter of 1985 plants of both species growing 
on a fence at Sunny Cliffs showed frost damage 
while Marsdenia plants growing inside shrubs 
nearby were unaffected (personal obser¬ 
vations). 
The two species were strikingly different in 
flowering behaviour. In Marsdenia flowering 
(and fruiting) occurs on a much higher pro¬ 
portion of plants than in Rhyncharrhena. There 
was regular November-December flowering of 
Marsdenia , even in very dry conditions, whereas 
Rhyncharrhena flowering only followed heavy 
rain. It is not known why heavy autumn rain can 
produce flowering of Rhyncharrhena but not 
Marsdenia , as in 1989. In Queensland rainforest 
“almost all liane species flower once a year, in 
early summer” (Hegarty 1988). If individual 
Marsdenia plants flower annually, summer 
flowering would mean that few or no plants 
would flower in the succeeding autumn. Neither 
species flowers or fruits in the cold conditions of 
winter; it seems that amount of fruiting is related 
to rainfall at other times, especially summer. For 
both species, rainfall can be sufficient to pro¬ 
duce flowering but be insufficient for any 
subsequent fruiting to occur. 
Marsdenia flowering phenology was categor¬ 
ized by Pate & Dixon (1982) as “flowers pro¬ 
duced annually during growth season”. 
It was hoped that artificial watering would 
produce widespread flowering and even fruiting, 
at least of Rhyncharrhena , but it only contri¬ 
buted to very limited flowering of that species. 
Watering a few shoots might not produce 
marked changes if those shoots were part of a 
very large clone covering most or all of the site, 
as is quite possible. 
For both species, large numbers of sucker 
shoots up to 300 mm high can appear in open 
areas adjacent to mature plants. This is es¬ 
pecially true in wet years like 1974-5, but plenty 
were found also in 1990 (Table 1). Before site 4 
was fenced, Rhyncharrhena sucker shoots were 
grazed right off for three successive years, prob¬ 
ably by kangaroos (T. Dominelli, personal com¬ 
munication). However, in unstocked areas near 
Red Cliffs lacking kangaroos and rabbits, large 
numbers of Rhyncharrhena suckers can appear 
after rain and then totally disappear during dry 
conditions, as they did in December 1990. In 
Marsdenia , only the smallest suckers die off 
during drought. 
Most such suckers are found in open areas, 
often on perennial grasses or on live or dead 
annuals, but also in completely bare areas. In 
Marsdenia , such suckers can remain small but be 
many years old. For both species, in the absence 
of a substantial aerial support the suckers re¬ 
main as small single shoots or die back; they do 
not form large, mature plants of shrub or creeper 
growth form, unlike Jasminum didymum (Cun¬ 
ningham et al. 1981, Hegarty & Clifford 1984). 
Casual observations of supported and unsup¬ 
ported seedlings (see seedling growth section 
above) suggest the potential for very rapid height 
growth responses to provision of support, as is 
the case for rainforest lianes (Putz 1984). 
Some of the striking phenological differences 
between Marsdenia and Rhyncharrhena may be 
because storage material in the tuberous roots of 
Marsdenia allows it to flower, fruit and retain 
leaves in conditions too dry for such behaviour 
in Rhyncharrhena. Work is needed to compare 
the water potential and intrinsic cellular resist¬ 
ance to desiccation of both species. 
FLORAL BIOLOGY 
Despite repeated observations, pollinators 
could not be found visiting flowers of either 
species. Rhyncharrhena is one of a number of 
asclepiads which has dark purple flowers (Good 
