WHY ARE PHRAGMITES AUSTRALIS CANADA'S WORST NVASIVE SPECIES

WHY ARE PHRAGMITES AUSTRALIS  CANADA'S WORST NVASIVE SPECIES

Have you heard of Phragmites australis?

If you have never heard of them, you definitely have seen them invading countless places including roadsides, ditches, and wetlands.

At first glance, these towering perennial clonal grasses reaching up to 5 metres skyward look impressive and rather benign - don’t let their harmless appearance fool you!  

Here’s a little history-

v arrived in North America at turn of century

v in 1980’s began to spread aggressively

v  now has a range  as far west as Manitoba, north of Sudbury,  ON and throughout Great Lakes Basin

v Globally cells/patches are  found as far as 70 degrees north and as far south as New Zealand and at altitudes as high as 3, 000 metres

 They are an impenetrable monoculture that is beginning to dominate wetlands while wiping the great biodiversity of native plant species.

  

 We need to protects and preserve our wetlands for the following reasons-

v provide food, shelter, and protection for amphibians, reptiles, waterfowl, and invertebrates

v  a great variety of plants, including a large number of threatened and endangered species grow in wetlands

v  plants such as bulrushes and cattails help to purify water, by absorbing and filtering pollutants improving the quality of groundwater

v  as the great variety of plants normally thriving in wetlands decompose they build up and enrich the soil

v  a multitude of wetland plants help to control and reduce flooding by storing water and releasing it slowly

v   wetland plants help protect shorelines from erosion by binding stream banks and by absorbing energy from waves

v people enjoy the opportunities for outdoor activities provided by wetlands such as bird watching, hiking, photography, canoeing, studying, and drawing wildlife 

Unfortunately, when phragmites invade wetlands and force out and eliminate native beneficial flora, then the myriad of benefits of wetlands disappear.

Recognizing Invasive Phragmites australis

FEATURES	NATIVE	INVASIVE - Phragmites australis
STEM DENSITY	low	high
STEM COLOUR AT BASE  (SPRING/SUMMER)	red to chestnut	tan
FLOWERING TIME	July	August
STEM TEXTURE	smooth and shiny	rough and dull
LEAF COLOUR	yellow green	blue-green
LEAF SHEATHS	fall off in autumn easy to remove	remain attached, difficult to remove

Factors Contributing to Colonization and Dispersal

(from research by Lynn Short, Professor, Faculty of Applied Science and Technology, Humber Institute of Technology and Advanced Learning) 

v have broad range of tolerance for environmental conditions

v can tolerate lake and  stream margins, water meadows, flooded plains, freshwater, and  estuaries

v have strong affinity for urban storm water catchments and agricultural run-off and Irrigating ditches

v spread easily when rhizomes are disturbed by human activity such as road construction

v increased use of chemical fertilizers has increased nitrogen in soils allowing phragmites australis to photosynthesize twice as fast as native phragmites

v  too much road salt discourages native flora, but  is favourable to Phragmites australis

v climate change with increasing temperatures has contribute to the growth of Phragmites australis

v will tolerate periodically dry soils as well as standing water a metre deep

v  have been found to grow in Acid Mine Tailings with very acidic soil

v in cases of drought root systems can penetrate to a depth of 3

  metres

v when growing in waterlogged soil specialized “water roots” are  created  to prevent roots from suffocating

v shoots emerge in early spring and will grow until early November

v shoots may grow 4 cm per day

v early shoots emerge from buds at the tips of rhizomes

v flowering occurs late in summer,

v seed mature from early August to late fall

v luckily from the over 2, 000 seeds produced per plume less than 5% are capable of germinating, but still a large number considering how many plumes there are in a stand of Phragmites australis

v its growing season is two months longer than native Phragmites

v when invading an area it outcompetes and displaces  native Phragmites, as well as, native and naturalized flora

v  dead leaves and very tall stalks create a thick thatch that suppresses other plants trying to grow

v they appear to have some allelopathic  (production of biochemicals)   capacity, although the effectiveness is not fully understood (Uddin and Robinson, 2017)

 “This capacity to rapidly produce a tall, dense canopy and its robust expansion of underground tissues allow Phragmites australis to suppress the growth of other plants.” Lynn Short, 2017

Why Phragmites australis are so Damaging

In 2005, Agriculture and Agrifood Canada named Phragmites australis the country’s worst invasive plant!

 They have had the most catastrophic impacts on wetlands and are the most difficult to control.

•      they pose an alarming threat to biodiversity and Species at Risk.
•     can alter the water cycle in a watershed
•     can change the level of the water table
•     dense underwater growth causing the buildup of sediments can eventually fill up a wetland
•     blocking of channels, diverting storm water runoff, and filling up  draining ditches can cause increased risk of flooding in some areas such as farmers’ fields or roadways
•     they can affect how groundwater is recharged 
•     destroy wetlands eliminating nursery and spawning habitats for fish - cloudy  and low quality water  
•     they have produced a significant loss of food and nesting sites for native North American wildlife 
•     rob fish and wildlife of nutrients
•     have had widespread negative impacts on the web of life causing the collapse of populations of insects and vertebrates that rely on their survival on shallow water zones
•     become death traps for endangered turtles, ducks, geese, and even deer and they threaten species at risk, such as Ontario turtles
•     result in monoculture completely eliminating much-needed biodiversity of flora and fauna and culturally significant wetland plants considered medicines by Indigenous Peoples.
•     the displacement of some native plants may put them at risk of extinction 
•     block shoreline views
•     reduce access to swimming and fishing 
•     cause difficulty with boat launching
•     dry dead standing stalks increase risk of fire

  Email your local representatives and urge them to provide much-needed funds to be forwarded to Invasive Phragmites organizations that are trying many costly strategies in their attempts to eradicate these very destructive grasses.

 So far all that governments and their community partners have been able to do are to manage and control Phragmites australis.