Lythrum hyssopifolia

A specialist plant of disturbed seasonal wet ground.


Grass-poly is a short, annual plant growing up to 20cm in height. The colour of the stems range from a light green to pinky-red, with many branches splitting off from the main stem. The leaves at the base of the plant are oval in shape and become more linear as they progress up the stem. The pink flowers grow individually or occasionally in pairs from the base of the upper leaves.


Grasspoly is a specialist of disturbed seasonally wet ground, areas which flood in the winter and dry out during the spring/summer. It is typically found in the hollows and ruts of arable land and damp pastures with winter disturbance by livestock or waterfowl.

Distribution and threats

Grass-poly faces a very high risk of extinction in Britain. It is currently only known from a handful of sites in the UK. It is protected under schedule 8 of the Wildlife and Countryside Act in 1981 and listed under Section 41/42 of the 2006 Natural Environment and Rural Communities (NERC) Act. This makes it an offence to pick, uproot or destroy any plant.

Its principle threats are field drainage, nutrient enrichment and the introduction of broad-spectrum herbicides.

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