Urban Alien Grasses
What are they?
This page covers a loose cluster of grass species that are not necessarily closely related but which are non-natives that all generally tend to be found growing as urban 'weeds'.
Where are they found?
The two typical origins of these plants are as seed contaminants of birdfood or self-seeding from plants grown as garden or amenity plants. Such plants may turn up in a wide variety of locations in urban environments, but in particular they are often found growing from cracks in pavements, walls, gravel areas or along the edges of cultivated borders.
Identification
Click here for help with some of the terminology used on the grass pages. These plants are brought together through their preference for similar habitats, so at least some of the species are relatively easy to identify due to the great variation in appearance of these plants. As with most grasses, details of the leaves (especially their ligules) and stems are important but close attention to the structure of the flower spike and details of the flower parts are important.
Rough Dog's-tail Cynosurus echinatus
Introduced from the Mediterranean region, with early records coming from coastal areas around docks. More recently as an urban alien and probably slowly increasing. Quite well established on coastal sands and gravels in the Felixstowe region. Flowers June to July. Annual plants, 10-100cm in height, typically solitary or in small tufts. Leaf blades 3-10mm wide, hairless but rough above, flat and long-pointed at the tip, wrapping closely around the stem at the base. Ligule membranous, up to 10mm long. Flower spike rounded, with the long-awned spikelets very tightly packed; one-sided with an obvious 'back' and 'front'. Spikelets 8-14mm, densely packed with sterile spikelets more or less concealing the fertile ones, the latter with 1-5 florets. Glumes 7-12mm long, very thin, keeled, one-veined. Lemmas 5-7mm long, awned from near the tip, the awns rough and 6-16mm long.
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Argentine Needle-grass Nassella tenuissima
Introduced from Southern South America as a garden and amenity ornamental. Increasingly spreading by wind-blown seed into public spaces in urban areas and now quite frequent in our region. Flowers June to July. Perennial plants, to 70cm in height, forming dense tussocks of very fine leaves. Ligule membranous, up to 2.5mm long. Flower spike multi-branched, narrow at first, spreading at anthesis, then narrow again when in seed. Spikelets greatly superceded in length by their awns. Glumes 5-8mm with long, fine-pointed apex. Lemmas 2-3mm long, with awns 50-90mm long. Forms dense tussocks of very fine, thread-like foliage that turns straw-coloured in autumn and persists - along with the old flower spikes - through the winter.
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New Zealand Wind-grass Anemanthele lessoniana
(Pheasant's-tail) Introduced from New Zealand as a garden and amenity ornamental. Increasingly spreading by wind-blown seed into public spaces in urban areas and now quite frequent in our region. Flowers July to August. Perennial plants, to 75cm in height, forming dense tussocks of long, arching leaves and arching flower spikes. Leaves rough on both surfaces, slightly blue-green above, flat, becoming strongly yellow-green to yellow-orange with age and eventually reddish-brown. Ligule mebranous. Flower spike multi-branched, narrow at first, spreading at anthesis, then narrow again when in seed; very long and with multiple branchlets at each node. Spikelets small and very well-spaced. Glumes 2-3.5mm. Lemmas 2mm long, with awns 6-8mm long. The autumn and winter tints to the vegetative parts are a distinctive feature of this species.
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Smilo-grass Oloptum miliaceum
Introduced to the UK from the Mediterranean region, variously as an accidental grain import, a wool-alien or as an escape from cultivation. Very rare in our area as yet, but may become more frequent with climate change as it is an abundant plant throughout much of southern Europe. Flowers July to August. A perennial to 150cm in height, forming large tufts or spreading colonies of stems. Leaf blades 2-5mm wide, lightly hairy and rough above. Ligule membranous, 1-1.5mm long. Flower spike very long, many-branched, with the branches becoming hardened and persistent into the winter. Spikelets 2-4mm, narrowly elliptical. Glumes 3-4mm long, more or less equal, membranous. Lemmas 2.5mm long, smooth and shiny, with an (often curved) awn 3-5mm long.
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Early Sand-grass Mibora minima
Native in westernmost parts of the British Isles but a rare introduction in our region, probably from mainland Europe. Persisted for some 50 years at a site in Suffolk but now gone from there. Recently discovered in Thetford, Norfolk as an urban weed. Flowers April to May. Annual plants, 2-15cm in height, typically forming small tufts. Leaf blades 0.5mm wide, smooth, narrow with an obtuse tip. Ligule membranous, up to 1mm long, blunt. Flower spike narrow and upright, 5-20mm long, one sided with the small spikelets arranged alternately along a central stem. Spikelets 1.8-3mm long, each with one floret. Glumes persistent, remaining after the seeds have dropped. Unawned, about two-thirds the length of the glumes.
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Strong-scented Love-grass Eragrostis cilianensis
(Stink-grass) Introduced from the Mediterranean region with wool waste and grain, but not established and only noted a handful of times. Flowers June to August. Annual plants, up to 75cm in height, typically solitary or in small tufts, the stems often with sunken glands at the nodes. Leaf blades 5-8mm wide, hairless but rough on both surfaces and with raised glands along the margins. Ligule membranous, 1-2mm long and with a fringe of hairs at the margin. Flower spike up to 20cm long, well-branched and rather open. Spikelets 2-4mm wide with 6-40 florets. Glumes 1.5-2mm long, keeled, with glands on the keels. Lemmas 2-2.8mm long, keeled, unawned. The glands on the plant produce a distinctive, rather pungent smell, which give the plant its English name(s).
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Small Love-grass Eragrostis minor
Introduced from the Old World tropics, probably with wool waste and grain, but not established and in our region only recorded once, from Cambridge (but recently). Flowers July to September. Annual plants, up to 60cm in height, but typically much shorter and forming loose tufts. Leaf blades 2-5mm wide, smooth or with a few hairs and with raised glands along the margins. Leaf sheaths variable but often with a good scattering of hairs. Ligule minute, reduced to a slightly raised rim. Flower spike 4-20cm long, well-branched and open. Spikelets 3-9mm wide with 6-10 (or more) florets. Glumes 1-1.7mm long, keeled, with glands on the keels. Lemmas 1.2-2mm long, keeled, unawned.
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Indian Love-grass Eragrostis pilosa
Introduced from the Old World tropics through a variety of means, but never becoming established and not recorded recently. Flowers August to September. Annual plants, up to 70cm in height but often much less, typically solitary or in small tufts; stems smooth and hairless. Leaf blades 1-3.5mm wide, hairless but rough on the upperside and along the margins. Ligule reduced to a minuscule rim. Flower spike up to 25cm long, but typically much shorter, well-branched and rather open. Spikelets 3-7mm wide with 4-14 florets. Glumes 0.5-1.5mm long, keeled. Lemmas 1.2-1.5mm long, keeled, unawned.
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Panic Veldt-grass Ehrharta erecta
Introduced from South Africa, though of uncertain origin. Twice recorded from the Ipswich-Felixstowe region. Flowers June to July. Annual plants, 50-100cm in height, typically in loose tufts. Leaf blades 3-10mm wide. Ligule membranous. Flower spike long, with long side branches that tend to droop downwards. Spikelets numerous with distinctly rippled lemmas.
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