Ecological Flora of the Central Chilterns

Transcription

1 Ecological Flora of the Central Chilterns Section 45: Poaceae: Pooideae, tribes Aveneae & Meliceae Yorkshire fog Tony F Marshall, M.A. (Cantab.) October 2018

2 Tribe Aveneae Yorkshire fog Holcus lanatus This is one of our most abundant and conspicuous grasses, a native perennial of rough grassland, hay meadows and most other places; in rich meadows it is often the dominant grass. En masse in flower it gives the appearance of a purple haze over a whole field - cue for a song? Identification It produces large tufts, difficult to remove, of greyish softly-hairy leaves and panicles of flowers which may be pale green but are often tinged pink-purple. The downiness of the whole plant gives it its fuzzy softfocus appearance. The ligule is of moderate length and blunt. Notable sites It occurs everywhere, even in open woodlands and bare wasteland, but is at its best in low-diversity meadows that are not cut before mid-summer, such as those behind Idaho Cottage and Michaelmas Farm, Prestwood, or across the road from the C of E primary school in Great Missenden. Ecological associates Same as for grasses generally (see Section 44); also three galls more specific to Holcus, but none recorded locally. The Small Skipper butterfly is particularly fond of laying its eggs on this grass. Human associations Generally a "weed" species, as it is too coarse for amenity grassland and spreads remorselessly, while being resistant to mowing or grazing. It is of low value for grazing stock. Derivation The appearance in flower across whole meadows makes the second half of the name very suitable, but that is not the origin. There are instances in the C14th of the word fog being used for aftermath, the grass that grows after mowing, of which Yorkshire fog is a prominent component. The word was probably Norse originally, and may be connected with the ancient Greek physaein "to blow or puff up". Our modern word "fog" meaning "mist" is no older than the C19th and probably derives from the Danish word meaning "spray, or rain drift". And why Yorkshire? It is no more and no less common in that county than elsewhere. Given the Norse, rather than Anglo-Saxon, origin of "fog", the designation "Yorkshire" was probably added to "fog" when the word spread to southern England, and so means no more than that it (the name, not the grass) was an import from "up north" Meadow dominated by Yorkshire fog, Idaho Farm, in June

3 45.2 Ligule of Yorkshire fog Panicles and upper leaves Yorkshire fog Mines of Liriomyza flaveola

4 45.3 Creeping soft-grass Holcus mollis Native perennial frequent only on light acid soils, quite widespread but much less abundant than Yorkshire fog, especially in meadows. Identification Different from Yorkshire fog in having at the least the upper sheaths on the stem hairless, except for a conspicuous tuft of white hairs at each node ("hairy knees"); much longer bent awns; and pointed jagged ligules. It is also much less densely tufted. Notable sites Typical locations are Widmere Field, Sandwich and Lodge Woods, and by Greenlands Lane allotments. It occurred in Haypole field before it was "improved" for horses. Ecological associates As for Yorkshire fog, but not so likely to attract small skipper. However, the moth Elachista canapennella tends to be particularly associated with Holcus mollis. Human associations None; much less weedy species than H. lanatus. Derivation "Soft-grass" would actually be a better name for H. lanatus, although non-flowering stems of mollis may be very downy. It is mat-forming rather than tufted, hence "creeping". The "hairy knees" are just visible in this photograph as white blobs.

5 45.4 False oat-grass Arrhenatherum elatius Abundant native perennial found in all kinds of grassy or waste spots. Identification Tall branched spikes have purple-and-silver tinged florets with two awns, one short, the other long and straight. It forms strongly-rooted tufts similar to Yorkshire fog. The ligule is short and blunt. Notable sites The grassy verges of allotments, fields and roads (eg Hampden Road), unkempt meadows (eg Boug's Meadow, although frequent cutting is reducing its prevalence there) and wasteland (eg Lovell Estate). Ecological associates The florets often feature small but conspicuous black lumps that are produced by the smut fungus Ustilago avenae, which can infect all our oat-grasses. The smut replaces the seed-grains. The flowerspikes may also be distorted by the smut Urocystis agropyri and the leaves dark-streaked by Ustilago striiformis. The seeds are said to be dispersed by ants. Derivation It is related to cultivated oat (see below) and shares the prominent awns that characterise all our "oats", but the awns are not as conspicuously bent as in other oats. Variation There is a variety bulbosum that grows in cultivated ground and has bulb-like swellings at the base of the stem, which help it to spread vegetatively when ground is ploughed. This variety (known as "onion couch") has not been noted locally, but it may well exist and needs seeking. Ligule The lower florets are showing signs of infection by Ustilago avenae

6 Yellow oat-grass Trisetum flavescens Common native perennial of grasslands, especially on chalk, but also frequent on neutral soils. Identification Rather like false oat-grass, but the florets are shiny yellow or golden-brown and the awns are clearly bent, giving the spike an untidy appearance as they protrude at all angles. Notable sites It occurs on most of our chalk sites - e.g. Prestwood Picnic Site, field-margins of Hampden Bottom Farm, Coombe's Orchards, Speen Access Land, Little Stocking Meadow. Ecological associates See false oat-grass for fungi that may affect it. I also often see ergot Claviceps purpurea on the spikes. Human associations It is used in seed-mixtures for meadows. Variation A larger foreign form ssp. purpurascens is sometimes introduced in seedmixtures and may be found in artificial grasslands, although not recorded locally. It has purple-tinged florets as well as being more robust with wider leaves (5mm or more) Yellow oat affected by Ustilago avenae

7 45.6 Wild oat Avena fatua This annual is essentially a weed of crops, probably brought in by early agriculturalists, and it can be found fairly regularly among crops or at the edge of cultivated land, helped by a degree of resistance to herbicides. Identification The spikes are long-stalked and drooping, each cluster with two or three florets, each which has a long bent awn. At the base of the cluster is a tuft of brown hair. Notable sites Most likely to be encountered with crops especially around Dirtywood Farm and at Collings Hanger Farm, but it also occurs occasionally in built-up areas like Prestwood. Ecological associates As for false oat-grass. Human associations On ripening the florets split up (disarticulate) into separate seeds, which enables effective seed dispersal. It is also quick-growing and seeds abundantly. These characters make it an effective weed, and also account for the phrase "sowing one's wild oats". Although cultivated oat was probably derived from it, the grains of wild oat are not suitable for human or animal fodder. Showning tawny tufts at base of florets Wild oats growing in wheat crop

8 Oat Avena sativa This European cultivar of wild oat was introduced as a basic crop many centuries ago. It sometimes occur as a relic of cultivation. Identification The flower clusters have only one or two florets, of which each may have no, one or two awns. There are no brown hair tufts at their base. The florets do not disarticulate like wild oat but fall as a cluster, and the whole plant is somewhat shorter. Notable sites It has been recorded widely but very infrequently - only 8 times in 20 years, most recently in 2018 in a wheat field on Collings Hanger Farm, where a few plants grew with abundant wild oat. Ecological associates As for other oats, but particular crop pests are the cereal leaf beetles Oulema melanopus and rufocyanea, blue-black with a red thorax, and it may be galled by several species not so far recorded locally. Human associations Major crop for both animal fodder (particularly horses) and man (porridge, oat-cakes etc). Derivation From the Anglos-Saxon āte "oats". This may have been a peculiarly British coinage, as the words for oats are quite different in other parts of Europe Downy oat-grass Avenula pubescens Native perennial of chalk grasslands, with only scattered records in our area due to agricultural improvement. Identification Lower and with a simpler erect spike than our other oats, Avenula still has the characteristic long bent awn to each floret. The ligule is long and pointed, and the leaf-sheaths hairy. Notable sites Little Stocking Meadow and Coombe's Orchards; perhaps still at Prestwood Picnic Site. Meadow oat-grass Avenula pratensis Native perennial of short chalk turf, with many fewer records than downy oat-grass, from which it differs principally by the lack of hairs on the sheaths. It has probably declined in frequency more than its congener because of the lack of grazing and hence lower frequency of short grassland. There have been no local records in this century, before which it had occurred at Acrehill Field, Little Stocking Meadow and a scrubby area south of Gomms Wood at Cryers Hill. It has probably disappeared from all of these because of lack of management and domination by coarser grasses.

9 Creeping bent Agrostis stolonifera Ubiquitous native perennial that spreads by above-ground stolons. Identification Like all the bents it has small one-flowered spikelets, which occur in panicles that spread open in flower but close up again afterwards. It is usually short. It has a long pointed ligule. Notable sites It would be difficult to specify where this plant does not occur, from natural grasslands to woodlands to built-up areas. Galls Four galls specific to bentgrasses are known, of which that of the mite Aceria tenuis is recorded locally. Other ecological associates The crown rust Puccinia coronata and the bent smut Urocystis agrostidis are recorded on creeping bent in our area. Human associations None. Creeping bent in flower Derivation Old English benne was a "reed-grass", from a stem common to many Germanic languages. It was applied to any coarse meadow grass. Variation Creeping bent is a very variable grass with a number of subspecies difficult to separate. No-one appears to have examined these locally; although most specimens are likely to be ssp. stolonifera, there are several others that might be present. Common bent Agrostis capillaris Native perennial preferring acid soils, on which it is quite widespread. Identification This is another creeping grass, but by means of underground rhizomes, not the overground stolons of Agrostis stolonifera. The panicles remain open after flowering, which can make it highly visible where it is the dominant grass, and the ligule is very short and rounded. Notable sites This is often the commonest bent in old acid grassland like Widmere Field, the parish churchyards at Prestwood and Great Hampden, Collings Hanger orchard, Sandwich and Peterley Woods. Ecological associates See creeping bent. Human associations It is often included in seedmixes for amenity grassland because of its capacity to create a dense sward. Ligule of creeping bent Creeping bent after flowering Common bent 45.8

10 Black bent Agrostis gigantea This perennial was an early introduction to this country as a weed of cultivation. It is fairly frequent in disturbed ground. Identification Taller than common bent (to 1.5m), with wider leaves (over 6mm) and longer rounded ligules (at least as long as wide). Notable sites It has been seen recently at Collings Hanger Farm, Great Kingshill allotments, Cobblershill, Little Kingshill and Hughenden. Derivation It is not apparent why this species should be termed "black", except that the flowers may turn dark purple, but then it has also been known as "white bent" and "redtop", so it all depends on which specimen you are examining. Perhaps the name comes from the farmer's perspective, with black equivalent to "bad", as it is a pertinacious weed and partially resistant to most herbicides Black bent Velvet bent Velvet bent Agrostis canina Native perennial of grassy places on wet acid soils. Given the infrequency of suitable habitat locally, it is quite uncommon. Identification It has stolons like creeping bent and similar long pointed ligules, but the panicle usually remains open in fruit. The florets often have short awns, which distinguishes it from the other bents above. Notable sites There are no local records for this century. In the 1980s and 1990s it was recorded in Rook Wood, Coach Hedgerow, fields at Great and Little Kingshill, and Prestwood Park. Druce (1926) only had it for Naphill Common. Derivation "Velvet" from the soft feel of the leaves. Variation Older records may include the very similar Brown bent Agrostis vinealis, which was previously classified as a subspecies of A. canina. It is very similar but has rhizomes instead of stolons and prefers dry to wet habitats. Both tend to have brown panicles that are conspicuous en masse.

11 Tufted hair-grass Deschampsia cespitosa Native perennial, mainly in our area in woodland, but also in rough damp meadows, a sign of infertile, frequently water-logged soils. Identification Huge tufts of rough leaves and tall stems to 1.5m or more, panicles widely branched with small 2-flowered spikelets, silvery where they catch shafts of sunlight. The ligule is very narrowly pointed. Notable sites Found typically in the higher parts of woods on clay where water is slow to drain and soil supports few other species of flower. Longfield. Monkton, Warren and Peterley Woods, Coach Hedgerow and Lawrence Grove, are good places to see it. It can also be abundant on the old wooded-over commons, like those at Great and Little Hampden. Galls One specific gall is known but not recorded locally. Other ecological associates Apart from the general grass-related species, the moths Small Dotted Buff and the grass-moth Agriphilla tristella are particularly associated with this species. Human associations None. Derivation The hair-grasses get their name from the fine branches in the panicle, although other grasses, like the bents, share this quality. Variation Our commonest subspecies is probably ssp. cespitosa, but ssp. parviflora also occurs, with narrower leaves and smaller spikelets (to 3mm), and hair-tufts at the base of each flower shorter, but ranges are overlapping and it cannot always be reliably separated. There is one record of ssp. parviflora from "Great Missenden" about 1996 (Jo Hall). Recorders have otherwise not recorded subspecies Wavy hair-grass Deschampsia flexuosa Native perennial of even more acid but much drier soils than cespitosa and therefore less widely distributed in our area. Identification Similarly tufted like cespitosa but not so tall (to 80cm), but leaves bristle-like, only about 0.5mm wide, and longer awns that more obviously protrude from the pinkish flowers. The ligule is short and rounded. "Wavy" refers to the fine branches often crinkled in appearance: although not a diagnostic feature it is a helpful indicator in picking it out. Notable sites With few recorded sites locally, the most likely places to see this grass are Lodge and Angling Spring Woods. It is abundant on heaths in the southern part of Bucks. Ecological associates No specific species are known, the narrow leaf-blades being less attractive to the moths using cespitosa.

12 45.11 Wavy hair-grass (Littleworth Common) Showing the crinkly branches (photo by Val Marshall) Sweet vernal grass Anthoxanthum odoratum Native perennial of all kinds of open grassland, widespread in our area and another of our commonest species. Identification Flowers in a simple, somewhat uneven, spike. Long white threads are prominent when in flower, these being the unusually long protruding stigmas. The ligules are rounded. Notable sites Hockey, Meadsgarden and Widmere Fields, Prestwood parish churchyard. Ecological associates I have seen it hosting the rust fungus Puccinia graminis ssp graminis. Human associations It is not nutritious enough to be sown for stock in improved pastures, but it is included in wildflower meadow mixtures. It smells like to new-mown hay when crushed. Derivation Flowers early, often in April.

13 Timothy Phleum pratense Common native perennial of meadows and sometimes wasteland. Identification Dense cylindrical spikes of flowers distinguish this grass and other species below, including the foxtails, and this is the largest with spikes up to 14cm long and 1 cm wide. The pair of glumes enclosing each floret are squared off at the top and each has a short but obvious awn at the tip, a good feature to recognise our Phleum species once known. Notable sites Long-grass meadows like Coombe's Orchards, Acrehill and Haypole Fields (although both of these have now been allowed to deteriorate), fields around Hampden Bottom Farm, and Bryants Bottom roadside. Galls There is one specific gall, but this is not recorded locally. Other ecological associates The larvae of the sawfly Cephus cultratus feed solely on timothy. Human associations Often included in hay meadow seed-mixes. Derivation It was originally referred to as "cat's-tail" from the appearance of the spike, but it was rechristened after it was promoted for cultivation by American farmer Timothy Hanson about 1720 in Britain Smaller cat's-tail Phleum bertolonii Native perennial of drier grasslands, more local in its distribution than timothy. Identification This species is basically smaller than pratense in most characters, but the ranges of each can overlap at the extremes, so that bertolonii may not always be recognised. Cope and Gray (2009) include the following measurements: usually under 70cm tall; leaf width less than 5mm; width of spike less than 7mm; length of spikelet less than 4mm; awn less than 1mm. If all these apply it can safely be termed bertolonii. Notable sites Often with timothy, as at Coombe's Orchards, Acrehill Field and Bryants Bottom roadside. Also recorded from 1988 to 2005 at Boug's Meadow. Meadow foxtail Alopecurus pratensis Native perennial quite common in meadows on rich soil. Identification Lacking the characteristic glumes of Phleum, the spikes of meadow foxtail have long awns, giving it its name after the longhaired tail of the fox. It flowers early, just after sweet vernal grass. Ligule short and blunt. Notable sites It is found quite widely, on Collings Hanger Farm (especially the orchard), throughout Hampden Bottom Farm, Boug's Meadow (1988 to 2012), Kiln Common Orchard, Haypole and elsewhere. Ecological associates None noted locally. Human associations Used in wildflower meadow mixes. Spike showing awns Spike in flower

14 Black grass Alopecurus myosuroides This annual was an early invader of this country as an agricultural weed. It is quite frequent and difficult to eliminate. Identification It has distinctly narrow pointed spikes that distinguish it from foxtails - its Latin specific name compares it to a mouse's tail. Notable sites Particularly prevalent among winter-sown crops on Hampden Bottom Farm and in fields neighbouring Lodge Wood. Ecological associates None have been noted locally. Human associations Crop pest. Derivation The spikes can become dark purple, which may explain the name, although the remarks under black bent above may also apply Marsh foxtail Alopecurus geniculatus Native perennial of wet places, not very common in our area. Identification Like meadow foxtail, but the stems start horizontally and then bend upwards at distinct knee-like joints (hence the Latin geniculatus). Notable sites It is still common at Doctor's Meadow by the River Misbourne and abundant in the (often dry) stream bed of the Misbourne through Abbey Park. It has been reported by several ponds, but may survive in few of them except perhaps the village pond at Speen. Marsh foxtail among water-cress,r.misbourne Marsh foxtail in flower Orange foxtail, Tring [Orange foxtail Alopecurus aequalis Never known in our area, this pond-side grass can be told from marsh foxtail by its orange pollen, less conspicuous awns, and much shorter anthers. It is now very rare but may still be found in the Chilterns. It grows by a pond on the Ashridge Estate, Hertfordshire.]

15 Reed canary-grass Phalaris arundinacea Native perennial of riversides and marshes, frequent where wet conditions continue to prevail. Identification Tall grass (it can reach 2 metres or so) in patches with large panicles of close-packed spikelets often tinged purple. The other frequent tall grass of similar habitats, other than reed, is Reed Sweet-grass (below), which has much more open panicles with narrow spikelets. Notable sites At various places all along the River Misbourne. Also planted at Sheepwash and Pickups Pond. It does not usually occur with reed, by which it is out-competed. Galls There are three galls specific to Phalaris, none recorded locally. Other ecological associates Apart from common grassassociates, this species may be affected by the rust fungus Puccinia sessilis, more often found on Arum. Human associations None. Derivation All tall riverine grasses tend to be called "reeds". "Canary-grass" is used of Phalaris species because the seeds of some (eg canariensis, below) are used for bird-seed. Variation The Mediterranean Bulbous Canary-grass P. aquatica, which can grow to 150cm but has a long dense spike, not a panicle (and is sometimes bulbous at the base) may be found as an introduction in cultivated ground and wasteland. It is sown as part of game-bird crops. It is also known as Harding Grass, probably from one of the farmers who brought it as a forage crop into America in the C19th (where it has become a pest species) Canary-grass Phalaris canariensis African annual occasionally found as a casual from spilled bird-seed. Identification Simple dense ovoid spike of whitish florets with green veins. Notable sites Recently seen along Lodge Lane, Cryers Hill Road and at Great Missenden station. The earliest record is Derivation As mentioned under the last entry the name probably derives from its use as bird-seed, although it could possibly be derived from the fact that it is native to the Canary Islands (as well as much of NW Africa). Variation The Mediterranean annual P. minor Lesser Canary-grass might be found, also from bird-seed. It has a narrower spike than canariensis and at least some of the glumes have toothed edges. Wood small-reed Calamagrostis epigejos Native perennial of the wetter parts of woodlands, locally uncommon. Identification Tall grass to 2m, growing in large patches, with bushy shortly-branched spikes, often purplish, and broad leaves (to 2cm). Each floret contains hairs as long as or longer than the lemmas. The ligule is long and attenuated. Notable sites Known from Lawrence Grove, Piggotts, Sandwich and Langleys Woods, and formerly along the ride in Angling Spring Wood before destroyed by forestry operations. Ecological associates Four galls are known to be specific to this grass, but there are no local records of any associated species. Human associations None. Derivation Superficially like a short reed. Also known as bush-grass, possibly from its habit of growing in dense colonies or from its bushy spikes in flower.

16 45.15 Wood small-reed: colony in Lawrence Grove, dead fronds in winter Wood small-reed panicles before flowering Water bent Polypogon viridis Mediterranean perennial long naturalised along canals in London, but now spreading more widely. First recorded in our area in 2008 and now quite widespread and. despite its common name, not restricted to obviously wet places. Identification Like creeping bent, but the panicle is more compact, neater-looking, with branches more regularly whorled. A small attractive grass, bright green early in the season, which embellishes the bare spots where it tends to grow. Notable sites I first saw it in our area at Hildreths Garden Centre, where it still grows abundantly beneath watered plant displays. Later in the same year I saw it in disturbed ground by Sheepwash Pond. Since then it has appeared in the stony ride through Monkton Wood and in pavement edges on Prestwood High Street. Although perennial, it tends to be short-lived and often acts like an annual. Ecological associates None known. Human associations None.

17 Annual beard-grass Polypogon monspeliensis Native annual of coastal saltmarshes in the south-east, occurring rarely as a casual in disturbed ground elsewhere, probably as a garden escape. Identification Like meadow foxtail (above), but broader spikes and longer awns, with long pointed ligules and glumes only minutely hairy (longhaired in Alopecurus pratensis). Notable sites Present in Naphill in 2007 and Monkton Wood in Ecological associates None known. Human associations Grown as an ornamental grass in gardens Early hair-grass Aira praecox Native annual of dry sandy heathland, generally common across Britain but rare in the Chilterns. It was said by Druce (1926) to be "locally common" in the Naphill area, but we have not seen it since and hardly have the right habitat for it. It is a small plant with narrow spikes of small awned florets, most noticeable in April or early May before flowering when the spikes are still enclosed in silvery bracts. It is dead and dried up by late July. Silver hair-grass Aira caryophyllea Another native annual like the last, from the same habitat, and not recorded since Druce (1926) documented it at Naphill, no doubt on the Common, which is now less suitable for it. It is also a low plant, although on average slightly taller than Early hairygrass, and the panicle branches are more open and not spike-like with silvery florets. Silvery panicles catching the sunlight

18 [Loose silky-bent Apera spica-venti First introduced long ago, this annual occurs as a casual among arable crops, probably as a result of grain contamination. It has not been recorded in our area, but does occur rarely from time to time in the Chilterns (I have seen it at West Wycombe). Large panicles, on tall stems, may be more or less open or crowded, with branches in whorls. The florets are shiny and have very long awns.] 45.17

19 Tribe Meliceae Wood melick Melica uniflora Common native perennial in ancient woods and hedgerows. Identification One of our prettiest grasses, especially curving out from a roadside bank with its sparse singleflowered purplish spikes nodding in the breeze on long delicate branches above bright green leaves. Notable sites Our chalk beech woods are the prime sites - Hampdenleaf, Longfield, Hatches, Acrehill, Nanfan, Stonygreen, Warren, Angling Spring, and Piggotts Woods - although it grows, less abundantly, in woods on clay as well. Ancient deeply sunken lanes are also good - Boss, Featherbed, Kingstreet, Whitefield, Greenlands and Hotley Bottom Lanes. Ecological associates We have no local records of associated species. Human associations None. Derivation "Melick" is from the late Latin melica used by Linnaeus for this grass, although it is unclear whether he invented this use, or where it came from. The Italian melica means "sorghum", a grass used for its grain, and may be related to Latin molare "to grind (like wheat)". Variation Another Melica species, altissima, Siberian melick, usually the dark purple cultivar 'atropurpurea', is grown in gardens and might occur as an escape. It has a very distinctive shaggy-looking narrow spike. Wood melick, Hotley Bottom Lane Siberian melick 'atropurpurea' Floating sweet-grass Glyceria fluitans This native perennial is our commonest pond grass by far. Identification The fronds usually sprawl untidily over the water surface, often in large patches, the flowers in long narrow spikelets on short stalks up the stem, which may lie on the water or bend upwards. Notable sites Sheepwash, Brickpits, Dennerhill, Peterley Manor Farm, Cherry Tree Farm, and Kiln Corner Ponds. Ecological associates The one specific gall is not recorded for our area, but typical associates are the leaf-miner Orthotelia sparganella, a moth, and the leaf-stripe smut Ustilago filiformis. Human associations The long yellow seeds were once used in soup or cooked as porridge. The leaves may accumulate "cyanogenic glycosides" which can be poisonous to stock, although only when they are in poor condition. Derivation The same glycosides give the grass a sweet taste, which attract cows to eat it, and it has been used as a fodder plant.

20 45.19 Floating sweet-grass Reed sweet-grass Glyceria maxima Frequent native perennial of riversides and large ponds. Identification This grass grows upright and tall and has longerbranched panicles of relatively shorter narrow spikelets. It can be confused with the equally tall Reed Canary-grass (see for differences). Notable sites Mostly along the River Misbourne - e.g. Deep Mill Pond. Ecological associates As for fluitans, but the mines of the moth Elachista poae also occur. Human associations Cows enjoy it and it has therefore been grown as a fodder plant. It is also used, like Reed (section 46), to prevent riverbank erosion. Variation A form variegata with decorative yellow-striped leaves is grown in gardens and is very invasive and difficult to eradicate if introduced to natural ponds (as at Wibner, Brickpits and Garden Centre ponds). Form variegata at Wibner Pond

21 Small sweet-grass Glyceria declinata Rare native perennial of ponds. There are two old records from the 1980s (unspecified site at Little Kingshill, and Brickpits Pond, Prestwood, where it no longer grows because of silting-up and competition from other plants), and one recent one from an unspecified site at Hughenden. I also recorded it nearby from Small Pond on Naphill Common in This is the smallest of our Glyceria species, usually only up to 70cm long, with spikelets up to 22mm and lemmas less than 6mm. It can be told from small specimens of the next species by the palea (innermost membrane of each floret) having two long narrow spines at the tip that protrude well beyond the sheathing lemma, which is also somewhat sharply toothed at the tip (only bluntly so in notata) Plicate sweet-grass Glyceria notata Rare native perennial of ponds etc. There is just one record from our area - Angling Spring Wood, where it has long grown in the vicinity of the spring. For differences from declinata see under that species. It is intermediate in overall size between fluitans and declinata and has lemmas similar in size to declinata. It is "plicate" (pleated) from the keeled sheaths (unlike fluitans but like declinata). Plicate sweet-grass by the spring in Angling Spring Wood