Skaneateles Conservation Area/Invasive species/Phragmites australis

Phragmites australis (common reed)

Non-native common reed (Phragmites australis ssp. australis), is very highly invasive in wetland areas such as the marshes and margins of the beaver ponds along Gully Road. It can rapidly form dense stands of stems which crowd out or shade native vegetation. It’s a perennial grass that can reach up to 20 feet high, with extensive underground rhizomes that extend even longer distances.^[2]^[3]

↑ Phragmites australis ssp. australis iNaturalist observations at the Skaneateles Conservation Area.
↑ Common Reed, Phragmites australis, New York Invasive Species Information 2021.
↑ Brittany L. Legaly (2019). Strategies for Controlling Invasive Plants in the Finger Lakes - A Project Guide for Problematic Plants of the Region - Terrestrial Edition. Finger Lakes PRISM.

Invasiveness ranking for Phragmites australis (common reed)

Phragmites australis ssp. australis is ranked as very highly invasive with a relative maximum score of 92%^[1] and is prohibited by New York State law.^[2]

1. Ecological impact (37/40)

1.1. Significant alteration of natural ecosystem processes (7/10)

Phragmites stands increase the fire frequency in marshes due to the dry material that persists above ground.^[3]

The extensive biomass produced by large stands increases the accretion of sediment and can lead to drying out of wetlands.^[4]

Dense stands also limit light availability. Uncertain whether changes are reversible.

1.2. Major alteration of natural community structure (10/10)

Stands can be incredibly dense eliminating all layers below.

1.3. Causes major alteration in natural community composition (10/10)

Stands can be so dense that they eradicate most or all native plant species formerly occurring in the area.

1.4. Severe impact on other species or species groups (10/10)

Can breed with the native Phragmites australis ssp. americanus, which is rare in much of its range, including New York. More data are needed on degree of breeding between the native and non-native subspecies. Phragmites in general is viewed as providing less valuable wildlife habitat than the native plant species it displaces. It provided low quality habitats for larval and juvenile fish.

2. Biological characteristics and dispersal ability (22/25)

2.1. Abundant reproduction (4/4)

Both abundant seed production (100s of seeds per plant) and extensive vegetative spread.

2.2. Numerous opportunities for long-distance dispersal (4/4)

Species readily dispersed long distances along water corridors.
Transport of seeds on animals is also possible.
Seeds are eaten by some birds.
Rhizome pieces can be dispersed.

2.3. High potential to be spread by human activities (3/3)

Small seeds can readily be transported by boats, railroads and other forms of travel through stands.

2.4. Two or more characteristics that increase competitive advantage (6/6)

Perennial
Can grow in poor soils
Fast growing
Secretes gallic acid, a potent phytotoxin, which may not support success.^[5]

2.5. Smothering growth habit, forms dense thickets (2/2)

Forms dense thickets.

2.6. Can germinate/regenerate in existing vegetation in a wide range of conditions (3/3)

Plant will germinate in a wide range of conditions of existing conditions.
Regeneration occurs in a wide range of conditions.
Can persist as small inconspicuous seedlings for 1-2 years until conditions become favorable.

Ecological amplitude and distribution

Forms large stands in marshes with few or no other invasives.

Wetland: Occurs in salt/brackish marshes, freshwater marshes, shrub swamps, ditches, beaches, and coastal dunes. Upland: Occurs in cultivated land and roadsides.

Can establish in freshwater marshes that lack any appreciable disturbance. Readily establishes in disturbed marshes.

Native range in temperate Asia is similar to that of New York State.

Present in all states and provinces in the Northeast and in all PRISMs in New York State.

Difficulty of control

Non-native Phragmites is a serious threat to rare and endangered species throughout North America (including the rare native subspecies P. australis ssp. americanus), and treatments using herbicides and mechanical means have been unsuccessful and often threaten the same species that they are trying to protect.

A few partially-successful attempts were made to control phragmites at the conservation area in past years. In the summer of 2016 when the beaver pond had mostly dried up, two 20x30-ft. tarps were laid over mowed Phragmites to attempt to kill it. The following year, when the beaver dam had been rebuilt and the tarps began to float and were removed, it was clear that that although no stems were growing initially where the tarps had been, large rhizomes, essentially 2-3-inch pipes were growing across them under the soil. Soon after that stems resprouted from these area.

A biological control program for Phragmites australis has been developed by Bernd Blossey’s team at Cornell University and their proposal to release two host specific stem miners was approved by The Technical Advisory Group for the Release of Biological Control Agents.^[6]^[7]

References for invasiveness ranking

Observations of Phragmites australis at the SCA

The following photographs and corresponding iNaturalist observations of Phragmites australis were made at or very near the Skaneateles Conservation Area. Click on images to enlarge and read details on Wikimedia Commons or on the "iNat obs" links to view the corresponding observations at iNaturalist.