Perennial, with downy, grey-green stems and leaves. It is a pest in the lawn as the paler colour and coarse leaves stand out from the finer grasses, especially at dusk.
Flowers July to September, with pink and white flowerheads which, viewed en-mass are said to resemble fog.
Grows to between 20 and 60 cm
Difficult to eradicate from the lawn. Patches can be slashed with a knife to damage the creeping stems, but for complete removal it may have to be dug out or killed off and the patch re-seeded or re-turfed.
Weedkillers to use:-
Glyphosate, systemic action, taken down into underground parts, which can be used on patches, but it will kill any surrounding grass hit during application. There is a new agent which contains pinoxaden, a highly selective herbicide which kills Yorkshire Fog and other weed grasses without affecting the finer species. It is used by cereal growers to kill weed grasses in crops but is not available to the domestic market so is mentioned here as an interesting footnote.

Creeping Soft Grass (Holcus mollis) is similar looking, but is hairy only at the nodes where the leaves attach to the stems.

Follow these links for further details on Weeds, Weed Removal and Weed Prevention.