Phalaris (Phalaris aquatica)
Status: pasture grass
A tall robust tussock grass, with an erect habit. Leaves are blue-green, flat and 1-2cm wide when mature. Tall erect stems carry dense cylindrical seed heads, consisting of numerous crowded overlapping flowers. Seeds have no awn, and are smooth and shiny.
Preferred habitat and impacts:
Valuable fodder in dry regions, but it needs to be heavily grazed as it quickly becomes rank and overgrown. Very invasive in remnant grassy native vegetation in farming areas.
Phalaris produces a lot of rank growth if not grazed and as this usually browns off in summer it can create a fire hazard.
Seed is spread by animals, in soil, on machinery and vehicles, and in water. The basal parts of the tussock may be broken up and spread in earth-moving or cultivation.
There are several species of phalaris, all similar in appearance. Another exotic grass found on the coast with a similar dense cylindrical seed head is pigeon grass (Setaria species), but it differs in having numerous short bristles protruding from the base of each flower, making the whole seed-head look like a miniature bottlebrush.
Heavy grazing early in the season can reduce seed set, but putting stock in after the plants have begun seeding will only spread the seed. Regular slashing can reduce seed set, and if cut frequently and hard enough, may kill plants. This can reduce the density of stands, making it easier to mop up the survivors with herbicides.
Dig or spot spray isolated plants, and remove the seed heads for safe disposal.