Family: Poaceae

Status:

Description:
A velvety greyish perennial mat forming grass, usually under 50cm high, which grows best in wet soils. Leaves blades are flat, to 10mm wide and softly and densely hairy. Flowering stems are erect with a seed head to 5-17cm long. The seed heads are highly variable in appearance, depending on their state of maturity. Initially they are spike-like, with the branches folded flat against the main stem, and purple in colour. During flowering the branches spread , making the whole head quite open in structure. As seeds mature the purple turns to straw colour, and eventually the branches contract against the main stem again. Despite all this variation in seed head appearance, the plant is easily recognisable by the velvety textured leaves.

Preferred habitat and impacts:
Yorkshire fog tolerates a wide range of conditions but is most invasive in wet soils in sunny or semi-shaded sites. It is not much grazed by stock and can become dominant in wet pasture. It may disappear in dry years, and become abundant in wet years.
It can be a serious weed of freshwater wetland margins.

Dispersal:
The seed is spread in mud on machinery and vehicles, and can adhere to animals and clothing. Viable seed can be spread in animal manure.

Look-alikes:
In their mature contracted straw-coloured form the seed heads are similar to those of another weed, sweet vernal grass (Anthoxanthum odoratum). This grass also has similar soft textured broad flat leaves, but they are bright green rather than greyish, and not velvety hairy. The photo shows the seed heads of both species, with those of sweet vernal grass being greener and narrower. A mature fog grass head is shown in the lower right corner of this photo.

Control:
Isolated plants should be removed before they seed. Control of well established infestations would be difficult, as the soil seed bank is large. Regular slashing may reduce its vigour, but this should not be done after seed production has begun, as it would only spread the weed further.