Nodding Greenhoods at GWR

The Nodding Greenhood, Pterostylis nutans, is one of Victoria’s most common terrestrial orchids. (Pteron = winged, stylos = pillar or column, nutans = nodding or drooping). The Nodding Greenhood is an abundant and widely distributed species. It usually flowers from mid-winter to late spring, depending on local and seasonal conditions.

Typical Nodding Greenhood colony

Nodding Greenhoods are often found in a variety of habitats; sandy-rocky, moist-dry, etc., but nearly always shady. Sometimes they may only be a few centimetres tall, or you might come across some as tall as 10-20cms or more.

All native terrestrial orchids are a highly evolved plant species that have a symbiotic relationship with other plants, fungi and insects. Consequently, terrestrial orchids play a significant role in determining the ecological importance of a particular habitat and their presence - or not - can be an important indicator of the health of an ecosystem.

Ground-hugging leaf rosette

Nodding Greenhoods die down through summer and their ground-hugging leaves, stems and flowers completely disappear. Their energy though is stored within underground tubers, and come next winter, they begin to appear above ground again, ready for the next stage of their evolvement.

Showing the labellum with hairs

Most pterostylis species depend on a fungus gnat for their pollination and fertilization. The insect is lured to the orchid flower by a pheromone where it is momentarily trapped within the hood by the labellum ‘snapping’ upwards. Pollen is transferred to the insect as it struggles to escape. Upon release, the gnat flies to the next flower, so transferring the packets of pollen it has inadvertently collected, ensuring healthy cross fertilization of the plants.

Unusual double-headed flower

While checking the nest boxes (5x Ringtails, 1x Kreft’s Glider and 1x Antechinus - we think) at the Golden Whistler Reserve in Drouin recently, the ‘bird nerd’ team ticked about a dozen colonies of Nodding Greenhoods with probably a total of several hundred plants in flower – including a rare ‘double-header’.

Trees and lightning

Lightning is created by the buildup of electrical charge within a cloud. The static electricity is created by the particles of ice and water droplets rubbing against each other. Positive charge is created at the top of the clouds and negative charge at the bottom.

Credit: Bureau of Meteorology

A large voltage difference is created as the charges build within or between clouds, or between the clouds and the ground. Eventually, a rapid discharge occurs – a massive electrical spark. The lightning bolt heats the air around it – to something hotter than the surface of the sun – which causes it to expand rapidly creating a shock wave which we hear as thunder.

When the discharge occurs to the earth, it usually seeks a tall structure such as a building or tall tree for conduction to the ground. Some trees, especially those of high moisture content, are ideal electrical conductors. As the current passes down the tree, enormous temperatures cause any moisture, sap, etc., to vapourize and expand rapidly – the tree can ‘explode’. When the charge reaches the ground, the surrounding root systems may be compromised and the tree may take several months to eventually die.

Depending on the species, moisture content, location, etc., the effect on the tree can vary considerably. The tree may be destroyed, ultimately die over time or the strike may have no effect at all. Most eucalypts seem to survive lightning strikes rather well, even multiple strikes.

Climate scientists tell us we can expect more thunderstorms as the climate heats up. Around the world, there is an estimated 8 million lightning strikes each day. Lake Maracaibo in Venezuela is the most thunderstorm-prone place in the world with about 300 storms a year. Darwin has about 80 thunderstorms each year.

 

Where will all the houses go?

Last year, 177,000 houses were built in Australia – the target set by the National Housing Accord was 240,000. To achieve the target, the NHA estimates an extra 34 km² of land will be needed – each year for the next 5 years.

Drouin Fields, Gardner & Holman Rd 670+? lots

Under the NHA, each state has a set of commitments and implementation schedules they have agreed to achieve. The Victorian Government has committed to:

            “introduce planning controls around select activity centres to deliver addition homes”

            “clearing planning backlogs at councils”

            “streamlining the planning approvals assessment process for housing development”

“reduce the need for planning permits for housing developments including permit exemptions for secondary dwellings”.

“continued work on Precinct Structure Plans by the Victorian Planning Authority.”

 

Hamilton Heights, McGlone Rd, 900+? lots

Drouin has an area of just over 50 km². The current ‘built up’ area of Drouin is less than 20 km². The current Precinct Structure Plan for Drouin covers an area of about 8 km² and is designed to accommodate 7,400 new dwellings.

Highfields Estate, Buln Buln Rd, 470+? lots

Perhaps we should be concerned for our town being impinged by developmental sprawl even further than it currently is. And, dare one hope that future development will be a little more sympathetic to our natural environment than current practices?