#52 A couple of winter Greenhoods

The Superb Greenhood really is a beauty. This was my first sighting, but I knew exactly what it was when I spotted it amongst the pine needles in the Watagans State Forest on the southern rim of the Hunter Valley in late July. I found only a single specimen.

Diplodium grandiflora - Superb (or Cobra) Greenhood

Diplodium grandiflora, formerly known as Pterostylis grandiflora, is commonly known as the Superb or Cobra Greenhood. Its flowering period is from May to July.

The habitat of the Superb Greenhood is amongst undergrowth on sandy soil in cool moist gullies. I found my specimen on a shaded grassy mound on the edge of a grove of introduced conifers.

It is a slender plant 15 to 25 cm high with two forms of leaves (ref: Native Plants of the Sydney District by Alan Fairley and Philip Moore). The stem-clasping (cauline) leaves are about 5 cm long and taper to an acute apex from a broad base, while a separate rosette of leaves is often absent at flowering time.

The lower sepals are erect, united in the lower third then abruptly contracting at the broad flat sinus (mouth of the flower) to 2 long points which extend high above the galea (top of the flower).

Back view of the lateral sepals

Stem-clasping leaves of the Cobra or Superb Greenhood

The Midget Greenhood (pictured below) was a great find in winter and spring of 2007 in Werakata National Park near Cessnock in the Hunter Valley. Its flowering period is July to October.

Hymenochilus muticus, Midget Greenhood, was formerly known as Pterostylis muticus. Its habitat is fairly dry open country. All my sightings were in small open patches amongst low scrub.

This orchid species varies from short and robust to about 30 cm tall and rather slender. It has small ovate to lanceolate leaves which are sometimes numerous in a basal rosette. It also has 3 to 8 closely sheathing stem bracts and a similar number of very small pale-green flowers in a spike-like raceme.

Midget Greenhood

The sepals are short and broad and joined for most of their length. They point downward exposing the short irritable labellum which has a thick dark basal appendage turned backwards.

The centre flower has the dark appendage exposed

Rosette of leaves of the Midget Greenhood

Although I haven't done much orchid hunting this year, I hope to get out and discover some more spring-flowering orchids as the warmer months approach.

More of my Greenhood Orchid posts

Blunt Greenhood - Pterostylis curta

Trim Greenhood - Taurantha concinna

Maroonhood - Pterostylis pedunculata

Tall Greenhood - Bunochilus longifolius

Nodding Greenhood - Pterostylis nutans

#27 Winter orchids

Before the official end of winter I'd like to show off some of the Hunter Valley's delicate and pretty Greenhood orchids. At a casual glance, ground orchids often go unnoticed amongst grasses and leaf litter, but they are well worth searching out.

The twisted labellum of the Blunt Greenhood

Last week I posted a brief outline of the biology of greenhoods, along with some pictures of the delightful Nodding Greenhood, Pterostylis nutans. I've found another four species in the mid and lower Hunter.

Blunt Greenhood, Pterostylis curta, is a charming flower with a twisted labellum (tongue), somewhat resembling a cheeky cartoon character. This twisted labellum is a distinctive identifying feature. A single stem up to 30cm tall emerges from a basal rosette of 3 to 6 dark green ovate stalked leaves, and bears a single flower. The flower is surprising large, up to 3.5cm height.

The flowering season of Pt. curta is from August to October, and it has been recorded in all eastern states of Australia, as well as South Australia. It can form extensive colonies, and I have seen it growing in moss over rock, moist sheltered areas, grassy woodland and leaf litter.

My Hunter Valley sightings in August of 2007 include Werakata National Park, Watagans National Park, Broke/Wollembi and Hunter Region Botanic Gardens. More information on Pterostylis curta is available at PlantNET.

A rear view of Pterostylis curta, Blunt Greenhood

Trim Greenhood, Taurantha concinna, which has recently had a name change from Pterostylis concinna, is another greenhood with a distinctive labellum, making identification a little easier. The apex of the redddish-brown labellum is notched, forming a 'fork'.

The plant is variable in height, depending on conditions, and I have seen it up to about 20cm high. It has long erect lateral sepals. Whilst the flower is predominently green and white, there are brown tints to the lateral (side) sepals and sinus (V-shape formed at the front of the flower by the lateral sepals). More information on Taurantha concinna at PlantNET.

I have observed Taurantha concinna, Trim Greenhood, growing in leaf litter and grassy open woodland at the Hunter Regional Botanic Gardens at Heatherbrae (May, Jun), and Werakata National Park near Cessnock (Jul, Aug).

The distinctive forked labellum of the Trim Greenhood

Long erect lateral sepals of the Trim Greenhood, in this specimen, sweeping inwards to touch.

Maroonhood, Pterostylis pedunculata, diverts from the usual green to display a dark reddish-brown flower. It has a solitary narrow flower atop a stalk up to about 25cm high. The tip of the labellum is just visible through the deep 'V' formed at the front of the flower by the lateral sepals. Lateral sepals spread upwards or backwards into long linear points.

I have seen Maroonhoods growing in dense colonies at Hunter Region Botanic Gardens at Heatherbrae in the Lower Hunter Valley in a shaded moist position amongst leaf litter in August 2007. More information on Pterostylis pedunculata at PlantNET.

A Maroonhood adorned with spider web. Notice the pointed labellum is just visible

Side and rear view of Pterostylis pedunculata

Rosette of dark-green ovate stalked leaves of Maroonhoods

A colony of Pterostylis pedunculata, Maroonhoods

Tall Greenhood, Bunochilus longifolius, was formerly known as Pterostylis longifolia. It has a long scape (or stem) up to 40cm high bearing lanceolate stem-clasping leaves between 3 and 8 cm in length. At some time in its life, this plant also has a ground-hugging rosette of leaves (although I have not seen this on the plants I found).

Several flowers on the single stem open in succession from the bottom to the top of the plant. Flowers are small (12mm high by 7mm wide) and are translucent green with darker green markings. Lateral sepals are narrow and point downwards exposing an extremely touch-sensitive brown and yellow labellum. More information on Bunochilus longifolius (synonym Pterostylis longifolia) at PlantNET.

Left, the irritable labellum of the Tall Greenhood has been triggered by disturbance to flip back against the column. Right, the labellum of another Tall Greenhood plant has reset itself awaiting an insect pollinator.

Tall Greenhoods that I found flowering in grassy open forest at Hunter Region Botanic Gardens in August 2007 were not growing in dense colonies, but in sparse groupings of 2 to 6 plants.

A Tall Greenhood plant showing leaves, fertilised ovaries developed into seed pods (the brown and green swollen growths), with the top-most flower still active.

And I'll finish my list of winter orchids with some Nodding Greenhoods, Pterostylis nutans, that I featured last week. It was such a delightful group that I couldn't resist photographing them.

#26 Greenhoods get the nod

The colour green is a rarity amongst flowers, which makes greenhoods rather special. But not only are these charming little native orchids green, they have an odd, almost comical 'alien' appearance, along with fascinating lives hidden amongst grasses and leaf litter.

Nodding Greenhood, Pterostylis nutans. Notice the pollen packages visible through the translucent hood - resembling frosted glass with green veins.

Late winter has been productive for my orchid hunting in the Hunter Valley, but rather than post several of my recent finds, I'm going to share some of the details of these remarkable natives and their secret lives, along with my images of the cute Nodding Greenhood, Pterostylis nutans.

My previous orchid biology entry gives a general and simple outline of orchid structure, but greenhoods defy the 'normal' petal and sepal structure (if indeed anything amongst orchids is 'normal' or constant).

Greenhood flower structure

Orchid flowers have three sepals and three petals, although at a casual glance, greenhoods don't appear to have this configuration.

Height is variable amongst Nodding Greenhoods. I have visited the colony below on Mount Royal Road east of Singleton over a couple of seasons, and found the plants were all from 4 to 6 cm high. They were growing in moss and lichen over rock. Nodding Greenhoods I've seen in the Lower Hunter growing amongst grasses in sandy soil have been much taller - up to 18cm. [I am presuming the yellow mass in the background is a slime mould]

As their common name suggests, greenhoods have a hood-shaped flower. The two lateral (side) petals and the dorsal (back) sepal have united to form a predominantly green, hood-like structure which protects the reproductive organs.

The two lateral sepals are fused together at the base to form the front of the flower, and protrude to form 'points' or 'ears'. These points generally extend above or to the side of the 'hood'. The third petal is the labellum (or tongue) which is hidden inside the hood.

The ovary of this successfully fertilised greenhood has swollen as seed develops.

In orchids, the male and female reproductive organs are highly modified and fused together, unlike most other plant families where the sex organs are separate.

The remarkable sex lives of Greenhoods

Generally, but not always, greenhood leaves take the form of a rosette of ovate ground-hugging green leaves. All greenhoods are deciduous. After seeds have been released, the above ground parts of the plant die and the plant exists as an underground tuber.

The the seed capsule dries and splits vertically to expose the dust-like seed to the breeze for dispersal. Notice at this stage, the stem has stiffened but is not yet dead - it holds the seed capsule erect in the breeze.

Pollinia (packages of pollen grains) are attached to the tip of the anther (male reproductive organ). The stigma (female reproductive organ) is located just below the anther, and receives the packet of pollen from a visiting insect, which is then transferred to the ovary where fertilisation occurs.

Greenhood flowers are usually pollinated by gnats, and sometimes mosquitos. I didn't know what gnats were, so I checked them out: gnats are common names for a large number of small, non-biting fly or mosquito-like insects in the order Diptera of the genus Mycomya. These tiny flies do not feed. They only live long enough to mate, lay eggs, and die. Eggs are laid in masses in the water or on aquatic vegetation, and larvae feed on living and dead plant matter.

Male gnats are enticed to greenhood flowers by a scent which imitates pheromones (chemical substances) emitted by females of particular gnat species.

The labellum is extremely sensitive to touch, and when triggered by a visiting insect, flips inwards towards the column, temporarily trapping the insect. A pollen package is either collected or received as the insect struggles to escape.

The greenhood flower does not offer nectar to the insect as a reward. This is sexual deception at its best. So the poor young gnat that only has a fleeting life in which to find and fertilise a mate, is duped by this clever little plant.

From a front-on angle, the Nodding Greenhood, Pterostylis nutans, has a sharp down-turned 'beak' and lateral sepals that form points facing the ground.

Cross pollination between different species is largely prevented by using different pollinators, or by placing the pollinium on a different part of the pollinator's body.

Survival strategies of the greenhood

This group includes some of the most drought tolerant orchids in Australia. Survival strategies include the large tuberoids which store moisture; the overlapping rosette of leaves which trap moisture and direct it to the root zone; and the tendency to grow in sites of plant litter accumulation and near rocks where run-off is concentrated.

A rosette of leaves of the Nodding Greenhood

I understand that the fleshy tubers are replaced annually. Dense colonies can also be formed by asexual (vegetative) reproduction, therefore allowing plants to produce offspring without sex.

Asexual reproduction can be made at any time, even before the plant is mature enough to produce seed via sexual reproduction in which insects or other external agents play a part. Vegetative offspring are 'clones' or carbon copies of the parent. The advantage with asexual reproduction is not having to rely on chance, however, the resulting limited genetic variation could be a disadvantage in a longterm evolutionary sense.

Some greenhood species flower more profusely after fire, but if fire destroys plants before seed is set, some species will be disadvantaged.

A colony of Pterostylis nutans, Nodding Greenhoods, amongst leaf litter in open forest in the Watagans National Park.

A taxonomic review of the greenhoods has split Pterostylis into several new genera, but the Nodding Greenhood has a distinctive appearance that is easily recognised. When next you see these charming hooded ground orchids or their many cousins, perhaps you will recall their kinky sex lives or their specialised survival characteristics. They might be small, but there is nothing 'ordinary' about greenhoods.

Greenhood Links

Michorrizal fungal association of greenhoods

Denis Wilson's greenhood observations

Greenhood key - PlantNET

Greenhood biology