American rat's tail grass

Identification
Upright grass 0.6-1.7m tall.
Long, narrow leaf blades 20-50cm long, 2-4mm wide.
Seed head is up to 45cm long, 3cm wide.
Seed heads change shape from 'rat's tail' when young to elongated pyramid shape when mature.
Difficult to distinguish from other pasture grasses and native Sporobolus grasses before maturity.
Unlike giant Parramatta grass, giant rat's tail grass does not develop sooty spike on its seed heads.
Can produce up to 85,000 seeds per square metre in a year, with initial seed viability of about 90%.
Significant portion of seed can remain viable for up to 10 years