Aimee Bliss slowly walks a bushland path outside Hobart, searching for some of Tasmania’s most fascinating plants at the edge of a dry forest.
This time of year many of the state’s orchids and carnivorous plants are in full bloom.
Aimee Bliss and her friend Chrissi Charles find a flower.(ABC Radio Hobart: Zoe Kean)
“Look,” Aimee says while pointing out a carnivorous plant called a sundew.
A tangle of tiny, pink flowers protrudes from the bracken. Just beyond are the glittering leaves of the sundew.
“It has little bugs stuck in its sticky parts. It will digest them and extract all the nutrients from them…amazing.”
The black spots on the sundew leaves are half-digested insects.(ABC Radio Hobart: Zoe Kean)
Aimee, an ecologist, enjoys spending her free time scouring the local woods for her favorite plants.
She is on the lookout for carnivorous plants and orchids, many of which are also in bloom at this time of year.
A little further on she discovers a large patch of bird orchids. At first they don’t seem to be blooming and she recognizes them by their distinctive pair of leaves lying flat on the ground.
“Wait a minute, there’s a flower,” she points, “ah, so cute.”
Bird orchids (Chiloglottis) are found in eastern Australia and New Zealand. (ABC Radio Hobart: Zoe Kean)
The flowers are named for their resemblance to baby birds begging for food.
Their wide mouths, bobbing up and down in the wind, look bizarre to human eyes – but to male wasps they are irresistible and ensnaring.
Late spring is a treacherous time to be in the Tasmanian forest… if you’re an insect.
Danger and deception are ever present for the tiny flying and crawling creatures of the bushveld.
Orchids that seduce insects
There are more than 1,700 species of orchids in Australia, including more than 200 in Tasmania, explains Katharina Nargar, who directs the orchid research program at the Australian Tropical Herbarium.
“Over 90 percent of Australia’s orchid species are found nowhere else on the planet,” says Dr. Nargar.
Many of the Australian orchids are tiny like this Caladenia species. (ABC Radio Hobart: Zoe Kean)
Some Australian orchids attract insects to pollinate them the traditional way, producing nectar for insects to drink. Other orchids are far more deceptive.
Aimee Bliss’ top tips for flower hunting
- Stay on the trail: it’s the best place to see flowers. If you stray, you could trample them
- Take photos but leave the flowers where you found them
- Wear clean shoes to avoid walking pathogens into the bush
“What’s special about orchids is that they’ve found a mechanism for really efficient pollination,” says Dr. Nargar.
“They bundle the pollen into packets, and the packets have some glue on them so they can attach a whole packet to the pollinator.”
These pollen packets mean “they put all their eggs in one basket”.
If they want to be successful in spreading their genetics, which pollen does, they need to make sure the pollinator quickly visits another flower of the same species.
Avian orchids increase their chances by forming “close relationships” with certain wasp species, says Dr. Nargar.
Male wasps swarming the forest looking for a suitable female in the foliage often use their scent to spot them.
Unfortunately for the male, avian orchids have evolved to produce just that scent. Not only that, but they also have a series of raised dark bumps on their petals that look like a female wasp.
A bird orchid seen by a wasp. The raised bumps on the flower look a bit like a female wasp.(ABC Radio Hobart: Zoe Kean)
The male lands to try to mate with the flower; when intoxicated, the pollen packet is attached to the wasp.
He then moves on and continues his search for a mate, but if his next lover is another orchid, it will be the flower that spread its genetics, not him.
Aimee spots a flower in a bird orchid colony.(ABC Radio Hobart: Zoe Kean)
“Australia is particularly rich in elusive orchids compared to the rest of the world,” says Dr. Nargar.
A type of greenhood orchid, this maroonhood uses sexual deception to fool fungus gnats.ABC Radio Hobart: Zoe Kean)
They form highly specialized relationships; Often a species of orchid is pollinated by a specific insect.
It is this specialization that Aimee admires when she discovers orchids in the forest.
“It’s like finding treasure, they’re so delicate and highly specialized,” she says.
Chrissi Charles photographs a bird orchid.(ABC Hobart: Zoë Kean)
carnivorous plants
Staring at another tangle of carnivorous plants, Aimee says, “They’re doing something that’s very unusual for a plant, they’re behaving almost like an animal by hunting.”
Botanist Laura Skates explains that Australia is a “hot spot” for carnivorous plants, with around 250 carnivorous plants calling the continent home to an estimated 800 species worldwide.
The poor soils of Australia set the stage for the multiple evolution of carnivorous plants on our old continent, as plants that can obtain their nutrients from prey have an advantage in these environments.
There are two genera or groups of these plants in Tasmania: the Utricularia, better known as bladderwort, and the Drosera, also known as sundew.
The glittering shooting stars on the sundew that Aimee found were a modified leaf, explains Dr. skates.
“These sticky tentacles can wrap themselves around the insects that come in contact with them,” she says.
In this WA sundew species (Drosera erythrorhiza) the modified leaves are very conspicuous.(Included in delivery: Laura skates)
“There are glands on the leaf surface that release digestive enzymes and break down the prey so the plant can absorb the nutrients.”
Sundews also need insects to pollinate them, leading to a “pollinator-prey conflict,” she says.
The flower of this sundew stands on a long stalk, so pollinators don’t get caught on the sticky leaves. (ABC Radio Hobart: Zoe Kean)
“You need insects for two different purposes: one for pollination and one for food.”
The great sundew discovered by Aimee resolved this conflict by having its flowers far away from their sticky leaves on long, spindly stalks.
