Common names: Dutchman’s Pipe
In my December Notes I mentioned the large number of seeds that had been left in the soil when we cleared out these vines. Thousands of these seeds have now germinated and they completely carpet many square metres of bushland. Spraying with a herbicide will be the only viable solution. I can only hope that the recent wet weather has caused most of the seeds to germinate so that we don’t have to face this problem over and over like we do with the Rivina humilis (Coral Berry).
Our last few working bees have focused on clearing the area below the southern side of the picnic ground. The main reason for this is to clear the severe infestation of Aristolochia elegans (Dutchman’s Pipe) creeper. This species is a declared class 3 pest in Queensland. It grows vigorously and smothers understorey trees and shrubs. Some of the creepers that were growing here had stems that were 4 cm in diameter and these vines carried dozens of old mature seed capsules that had already released their seeds onto the ground. It is possible that this patch of plants has already released 100,000 seeds! I suspect that this means that we can look forward to several years of serious weeding in this area to eliminate this pest from the reserve.
As well as smothering native vegetation, this weed is also toxic to the larvae of Richmond Birdwing (Ornithoptera richmondia) and Clearwing Swallowtail (Cressida cressida) butterflies. If these butterflies lay their eggs on the Dutchman’s Pipe vines the larvae die before they reach maturity (unless the larvae feed only on the flowers). The photo below shows their spectacular flowers and an empty seed capsule that contained many hundreds of flattish heart shaped seeds.
This species seems to be appearing in increasing numbers as natural regeneration occurs in the weeded areas. It is the main host plant in the Reserve for Clearwing Swallowtail butterflies. Finding these plants can be quite difficult as they are normally quite small with only about 6 or 8 leaves, but it doesn’t seem to pose too much of a problem for the butterflies because all but one of the plants I found had already been visited by a butterfly that had laid an egg or two on the leaves. The eggs are visible in the photograph as the bright yellow spots.
This species possesses an amazing ability to flower and fruit on very young plants. I wonder if this ability to produce fruit and seeds very quickly has evolved in response to the predation by the Clearwing Butterfly caterpillars. These caterpillars can strip the plant bare very quickly indeed! So the plant needs to produce seeds quickly before it is found and destroyed.
This previously undescribed plant species Aristolochia sp. (D’Aguilar Range L.H.Bird+ AQ520943) has now been classified as Aristolochia meridionalis subsp. meridionalis. It continues to come up in small numbers at the bottom of the bank below the picnic area. However the plants don’t seem to be there very long before they are discovered by a Clearwing Swallowtail butterfly which lays an egg or two on them. The developing caterpillars then proceed to defoliate the plants. It is quite amazing that the butterfly can find such small and uncommon plants in the middle of the forest!
Common name: Richmond Birdwing vine
I have planted into the reserve just over a dozen plants of Pararistolochia praevenosa (Richmond Birdwing Vine). While I have no specific evidence that this species ever grew in the reserve it did originally grow right across the Brisbane area. It is the most common host plant for the Richmond Birdwing butterfly. The Richmond Birdwing Conservation Network is trying to establish a patchwork of these plants throughout SE Queensland and Northern NSW. We have four large vines growing in our garden and they provided the seeds for these plants. I suspect that this species may be difficult to transplant, but once established these vines seem to be remarkably hardy and drought tolerant. As they say “if you plant it, they will come”. However, although we’ve had our plants for about ten years I’m yet to see a butterfly. (February 2013)