Velvet grass

style="background:#Template:Taxobox colour;"|Holcus lanatus
File:Holcus lanatus Gestreepte witbol (2).jpg
style="background:#Template:Taxobox colour;" | Scientific classification
Kingdom: Plantae (unranked) Monocots (unranked) Commelinids Order: Poales Family: Poaceae Genus: Holcus Species: H. lanatus
Binomial name
Holcus lanatus L.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Holcus lanatus, known as Yorkshire Fog or velvet grass, is a perennial grass. The specific epithet lanatus is Latin for 'woolly' which describes the plant's hairy texture.

In parts of northern Europe the grass is a common native grass species and a hardy pasture grass. Yorkshire Fog, tufted grass and meadow soft grass are the common names used. In North America, where it is an invasive species, the names are velvet grass or common velvet grass.

Characteristics and hybrids

File:Holcus.lanatus.3.jpg

Flower showing anthers

Holcus lanatus has velvety grey-green leaves. The shoots are round. The base of the shoots are white with pink stripes or veins - these are used in identification and are known by certain ecologists as 'stripey pyjamas'. The inflorescence is robust and often tinged purple. It produces a large amount of seed and is a rapid coloniser of disturbed ground. It prefers wetter ground, often seen around drainage ditches. The ligule is 1-4mm long, blunt and hairy.

Holcus lanatus can also be told apart from H. mollis by its beardless nodes on the culm; the absence of rhizomes; the awn of the upper lemma becoming hooked when dry and not projecting beyond the tips of the glumes.

It spreads vegetatively by developing new shoots and roots at its nodes. Plants form a blanket of runners on the soil surface. Semi-prostrate rosettes of shoots called 'mops' may form at the end of the runners. These mops root readily in contact with moist soil.

A male sterile hybrid with Holcus mollis exists with 2n = 21 chromosomes. Hybrids tend to resemble H. lanatus in their morphology.

Invasive species and habitat preferences

File:Gestreepte witbol bloei Holcus lanatus.jpg

Mature flowers

In a European survey of weed seed contamination in cereal seed in 1970, Holcus lanatus was found in 1% of samples. All of this was home saved seed. H. lanatus is an indicator of poor soil, too low stocking or poor drainage. It is tolerant of ranges of soil pH, but grows best between pH 5.0 and 7.5; exhibits climatic tolerance over a wide altitude range; severe frosts kill H. lanatus under certain conditions; and it does not survive trampling and puddling. It can be controlled in some European locations by increasing available potassium and phosphorus, increasing stocking rate and improved drainage. This is not effective in North America.

Noxious weed

Holcus lanatus is a significant pest weed in Australia, as it is a winter growing C₃ grass and survives droughts and hot summers as seed. It is distasteful to stock unless young and not much else is available. The flowers are wind pollinated and out-crossing predominates. The seeds start to become viable 5 to 9 days after flowering and are completely viable after 20 days. Seeds are shed from June to early autumn. Seed numbers per panicle range from 100 to 380. The average seed number per plant ranges from 177,000 to 240,000 depending on time of emergence.

Invasive species

In North America, Holcus lanatus is an invasive species in native grasslands and disrupts other ecosystem also. In Yosemite National Park it is one of nine priority noxious weeds to control for habitat restoration and regenerating native plant balances. H. lanatus forms a dense stand that can exclude other plants and may reduce or eliminate native Poacea species and other Genrera diversity.

Insect foodplant status

Holcus lanatus in its natural habitat is a food source for the Speckled Wood, Wall and especially Small Skipper butterflies. It is rarely utilized by the Essex Skipper. In its native range it may occur in plant associations such as the Juncus subnodulosus–Cirsium palustre fen-meadow habitat.

See also

• Invasive grasses of North America

References

Bibliography

• C. E. Hubbard (1976). Grasses. Harmondsworth: Penguin Books. ISBN 978-0-14-013227-4.

External links

• http://www.hdra.org.uk/organicweeds/weed_information/weed.php?id=81
• Grasses of temperate Australia, Lamp, Forbes and Cade. First published 1990, Bloomings Books. ISBN 0-646-41189-6
• California Invasive Plant Council (CAL-IPC): "Invasive Plant Database"