Finger-grasses
What are they?
This page covers a group of grasses that can look rather similar due to their flowerheads, which typically consist of a series of long, finger-like branches with the florets arranged along the branches. The individual branches may all stay more or less parallel to each other, or may diverge greatly, like the spokes of a wheel or an inside-out umbrella.
Where are they found?
Grasses with finger-like flowerheads are common in warmer climes, particularly in tropical Africa and into the Mediterranean region, but tend not to occur in northern Europe, so these are all introduced species. Thus, they typically turn up on disturbed ground or in urban environments.
Identification
Click here for help with some of the terminology used on the grass pages. Identification of this group to genus is mostly straightforward based on the overall size and appearance of the species, but the true finger-grasses in the genus Digitaria are all rather similar and identification requires close attention to the flower parts, including measurements.
Smooth Finger-grass Digitaria ischaemum
Introduced annual from southern Europe, probably most often as a seed contaminant. Less than 10 scattered records from across our region. Flowers August to September. Plants 10-35cm in height and typically forming tufts. Leaf blades 2-7mm wide, flat, hairless, or with a few isolated hairs at the base. Leaf sheaths smooth, sometimes with a few isolated hairs at the top. Ligules membranous, 1-2mm long. Flower spike with 2-8 branches, emerging close together but eventually spreading out broadly. Spikelets 2-2.5mm, each with two florets, arranged in pairs or threes, on one side of the main stem. Upper glume (nearest the main stem) and lower lemma more or less the same length; lemmas minutely pubescent. Florets typically broader and less pointed than those of Hairy Finger-grass.
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Hairy Finger-grass Digitaria sanguinalis
Introduced annual from southern Europe, probably most often as a seed contaminant. Scattered records from across our region, especially around Norwich and Cambridge. Flowers August to October. Plants 10-60cm in height and typically forming sprawling tufts. Leaf blades 3-10mm wide, flat, hairless or hairy. Leaf sheaths typically downy to hairy but sometimes smooth. Ligules membranous, 1-2mm long. Flower spike with 4-10 branches, emerging close together but eventually spreading out broadly. Spikelets 2.5-3.3mm, each with two florets, arranged in pairs, on one side of the main stem. Upper glume (nearest the main stem) usually less than a half the length of the lower lemma; lemmas with flattened hairs. Florets typically narrower and more pointed than those of Smooth Finger-grass.
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Tropical Finger-grass Digitaria ciliaris
Introduced annual, probably as a seed contaminant. A single record from Norwich in 1971. Flowers August to September. Plants to 90cm in height, though often much less. Leaf blades 4-8mm wide, flat, hairless or with a few hairs near the base. Leaf sheaths with scattered hairs, or sometimes smooth. Ligules membranous, 1-2mm long. Flower spike with 2-9 branches, emerging close together but eventually spreading out broadly. Spikelets 2.6-3.6mm, each with two florets, arranged in pairs, on one side of the main stem. Upper glume (nearest the main stem) more than half the length of the lower lemma; lemmas with silky hairs along the margins.
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Bermuda-grass Cynodon dactylon
Introduced perennial, probably from southern Europe, despite the English name. Less than 10 scattered records from across our region and not persisting, though long-established not far away on the coast at Shoeburyness, Essex. Flowers August to September. Plants 8-30cm in height and forming patches by means of both creeping stolons (rooting at the nodes) and rhizomes. Leaf blades 2-4mm wide, flat, hairless or lightly hairy. Leaf sheaths short and rounded. Ligules a dense row of short hairs, 0.5mm long, surrounded by longer hairs on the leaf base. Flower spike with 3-6 branches, emerging close together but eventually spreading out broadly. Spikelets 2-2.8mm, each with a single floret, in two rows on one side of the main stem. Differs from the finger-grasses in being much smaller, perennial and forming creeping patches that can become extensive.
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Indian Wire-grass Eleusine indica
(Yard-grass) Introduced annual from the Old World tropics. Less than 10 records from Norwich, Cambridge and Colchester. Flowers August to September. Plants 30-90cm in height but often much less if growing on well trodden ground. Leaf blades 3-8mm wide, flat, hairless or slightly rough on the margins. Leaf sheaths keeled. Ligules membranous, 0.5-1mm long. Flower spike with 2-15 branches, emerging close together but eventually spreading out broadly. Spikelets 3.5-7.8mm, each with 3-9 florets, in two rows on one side of the main stem.
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Chinese Silver-grass Miscanthus sinensis
Introduced as a garden ornamental in a variety of forms and occasionally planted in the wider countryside as pheasant cover. Flowers August to September. Plants 60-300cm in height and typically forming dense, compact clumps with stems less than 10mm thick. Leaf blades up to 1m in length and 6-20mm wide, green with a pale midrib, or may be purple or banded with cream in ornamental varieties. Flower spike consisting of a series of long, finger-like spikes. Spikelets 3.5-7mm, each with two florets, the lower sterile, the upper fertile. Lemmas with long, bent awn.
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Giant Silver-grass Miscanthus x giganteus
An artifically created hybrid that is being increasingly planted as a crop to be converted to bifuel. Occasional plants are found on roadsides and rough ground. Flowers August to September. Plants 200-400cm in height, the stems at least 10mm thick. Leaf blades up to 1m in length and 6-20mm wide, green with a pale midrib, or may be purple or banded with cream in ornamental varieties. Flower spike consisting of a series of long, finger-like spikes. Spikelets 3.5-7mm, each with two florets, the lower sterile, the upper fertile. Lemmas without awns.
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