Phalaris aquatica

It is an erect, waist-high, stout perennial bunch grass, with grayish to bluish green leaves. Flowering heads are dense, spike-like, and usually 2 to 5 inches (50 to 125 mm) long. It is slow to develop from seed, but can form large bunches after several years.[3]

Phalaris arundinacea (reed canary grass) differs from Harding grass in having more distinct rhizomes, and an inflorescence that is compact at first but becomes more open as the branches spread.

Hybrids of Harding grass and reed canary grass have been produced. Varieties include 'AQ1', 'Uneta', and 'Australis'.

P. aquatica is a quick-growing grass which incorporates and utilises soil nitrogen rapidly.[4]^{: 169–174}

Phalaris aquatica originated from Southern Europe and the Caucasus. It is naturalized in South Africa, Australia, New Zealand and the USA.[5] Although very recently introduced there, its pasture value was first recognised in Australia.[6] Domesticated cultivation then spread to the United States, Argentina and several other countries in South America, and New Zealand.[6]

Leaves and seedlings contain gramine.[7]

Phalaris aquatica is a pasture species grazed by ruminants. The grass can also be cut, providing good quality fodder for grazing livestock for 8 to 12 months a year.[5]

Some Phalaris species contain gramine, which can cause brain damage, other organ damage, central nervous system damage and death in sheep,[7] although Phalaris aquatica is said to be non-toxic to them.[8]

Seeds

In Victoria, Australia, it is reported that kangaroos grazing on Phalaris aquatica may develop a condition known familiarly as "Phalaris staggers", in which coordination and mobility are affected.[9]

Harding grass is an invasive species in grassland, oak woodland, chaparral, and riparian habitats. Native grasses and grassland habitat in California are affected.

• Jepson Manual Treatment