ユウゼンギクはキク科シムフィヨトリクム属の栽培種。以前はシオン(アスター)属に分類されていたため、宿根アスターともいわれる。日本には明治時代に渡来し、シノノメギク東雲菊ともいわれる。園芸品種は多数ある。
　多年草、高さ17～100(～140)㎝、緩い群落をつくり、ときに叢生、長い根茎がある。茎は1～5+本、直立(真っすぐ、丈夫～細く、しばしば赤色を帯び)、無毛で、上部の線上に毛があり、ときに、全体に伏した剛毛状の長軟毛（strigoso-pilose）がある。葉は厚く、堅く、±肉質、縁はざらつき、先は微突形、面は無毛、下面の中脈はときに絨毛がある（var. villicaule)。根生葉は花時に枯れ、葉柄がある(葉柄は翼があり、基部は鞘状)。葉身は卵形～卵状披針形～披針形、長さ17～60+㎜×幅6～11+㎜、基部は漸尖形～楔形、先は鈍形。下部の茎葉は花時までに枯れ、無柄又は広い翼のある柄があり（葉柄が抱く）、葉身は槍状卵形～槍状倒卵形～楕円形～線状披針形、長さ40～200㎜×幅4～40㎜、基部は楔形又はときにわずかに漸尖形、ときに円形又はわずかに耳があり、わずかに抱き、先は円形～尖鋭形。上部の茎葉は無柄、葉身は槍状卵形～線状披針形、長さ13～62㎜×幅3～15㎜、上部で次第に小さく、基部は楔形又はほぼ円形、ときに、わずかに耳状になり、±抱き、縁はまばらに細鋸歯があるか又は全縁。頭花は開いた～密な円錐花序状につき、枝は±散開～斜上、葉があり、葉は離れ、小さく、枝葉は次第に小さくなる。花序柄は長さ4～41㎜、無毛又は中程度に軟毛がある。苞は1～3個、披針形～卵形～線状倒披針形、抱いて基部に着く苞はときに総苞を超え、ときに、総苞片に格付けされる。総苞は鐘形、長さ6～9㎜。総苞片は3～4列につき、長円状倒披針形又は長円状へら形（外総苞片）又は長円状披針形～線状披針形～線形(内総苞片)、不等長～類等長、基部は1/5～1/3硬化し、縁は透明、薄膜質、微細不整歯で、上部にまばらに縁毛があり、緑部分は披針形、ときに葉状、先は広がる～±ささくれ状になり、普通、鋭形～鈍形、または±長い尖鋭形、微倒頭、面は無毛。周辺小花は15～35個、花冠は青紫色又は紫色、まれに、ピンク色又は白色、舌部は長さ(6～)10～19㎜×幅0.9～2.1㎜。中心小花は28～68個、花冠は黄色、赤褐色～紫色になり、長さ4～7.5㎜、筒部は漏斗形～鐘形ののど部より短い。裂片は披針形、長さ1～1.5㎜。痩果はタン色～褐色、倒卵形、扁平、長さ2～4㎜、4～6脈があり、面にはまばらに剛毛がある～ほぼ無毛。冠毛は汚白色～黄色、長さ4～6㎜。花期は8～10月。4変種と多数の品種がある。
品種)　'A.M. Carr' , 'Ada Ballard' , 'Albanian' , 'Aldenham Pink' , 'Alderman Vokes' , 'Alex Norman' , 'Algar's Pride' , 'Alice Haslam' , 'Alpenglow' , 'Amethyst' , 'Angela' , 'Angela Peel' , 'Anita Ballard' , 'Anita Webb' , 'Anneke' , 'Antwerp' , 'Antwerpse Parel' , 'Apollo' , 'Apple Blossom' , 'Aramis Rose' , 'Arctic' , 'Asflo Blue' , 'Audrey' , 'Autumn Beauty' , 'Autumn Days' , 'Autumn Glory' , 'Autumn Princess' , 'Autumn Rose' , 'Baby Climax' , Bahamas = 'Dasone' (Island Series) , Barbados = 'Dastwo' (Island Series) , 'Barker's Double' (d) , 'Beauty of Colwall' , 'Beechwood Beacon' , 'Beechwood Challenger' , 'Beechwood Charm' , 'Beechwood Lady' , 'Beechwood Pink' , 'Beechwood Rival' , 'Beechwood Supreme' , 'Belmont Blue' , 'Benary's Composition' , 'Benedikte Viking' , 'Bente Pink' , 'Beth' , 'Bewunderung' , 'Blandie' , 'Blauglut' , 'Blaukuppel' , 'Blue Baby' , 'Blue Bouquet' , 'Blue Boy' , 'Blue Danube' , 'Blue Eyes' , 'Blue Gem' , 'Blue Gown' , 'Blue Jacket' , 'Blue Lagoon' , 'Blue Lapis' , 'Blue Moon' , 'Blue Orb' , 'Blue Patrol' , 'Blue Plume' , 'Blue Radiance' , 'Blue Spire' , 'Blue Whirl' , 'Bluetenwolke' , 'Blutenmeer' , 'Bonanza' , 'Boningale Blue' , 'Boningale White' , 'Bonnie' , 'Bonningdale White' , 'Borealis' , 'Bridesmaid' , 'Bridgette' , 'Brightest and Best' , 'Brigitte' , 'Caborn Pink' , 'Cairo' , 'Calgary' , 'Cameo' , 'Camerton' , 'Candelabra' , 'Cantab' , 'Cantonese Queen' (v) , 'Carlingcott' , 'Carnival' , 'Catherine Chiswell' , 'Cecily' , 'Charles Wilson' , 'Charlotte zur Linden' , 'Charnwood' , 'Chatterbox' , 'Chelwood' , 'Chequers' , 'Chicago' , 'Chilcompton' , 'Christine Soanes' , 'Cliff Lewis' , 'Climax Albus' , 'Cloudy Blue' , 'Colin Bailey' , 'Colonel F.R. Durham' , 'Coombe Delight' , 'Coombe Gladys' , 'Coombe Joy' , 'Coombe Margaret' , 'Coombe Pink' , 'Coombe Queen' , 'Coombe Radiance' , 'Coombe Ronald' , 'Coombe Ronald' , 'Coombe Rosemary' , 'Coombe Velvet' , 'Coombe Violet' , 'Countess of Dudley' , 'Court Herald' , 'Crimson Brocade' , 'Crimson Velvet' , 'Dandy' , 'Daniela' , 'Daphne Anne' , 'Dasandre' (PBR) , 'Dasash' (PBR) , 'Dasbri' (PBR) , 'Dascar' (PBR) , 'Dascel' (PBR) , 'Dasdebi' (PBR) , 'Dasdem' (PBR) , 'Dasfour' , 'Dasgra , 'Dasjes' (PBR) , 'Dasjul' (PBR) , 'Daskat' (PBR) , 'Dasmar' (PBR) , 'Dasone' , 'Dasthree' , 'Dastwo' , 'Dauerblau' , 'Davey's True Blue' , 'David Murray' , 'Dazzler' , Debbie = 'Dasdebi' (PBR) (Mystery Lady Series) (d) , Demi = 'Dasdem' (PBR) (Mystery Lady Series) (d) , 'Desert Song' , 'Destiny' , 'Diana' , 'Diana Watts' , 'Dietgard' , 'Dolly' , 'Dora Chiswell' , 'Dorothy Bailey' , 'Dunkerton' , 'Dusky Maid' , 'Dusky Maid' , 'Dwarf Ibiza' , 'Dymbro' , 'Eclipse' , 'Elizabeth' , 'Elizabeth Bright' , 'Elizabeth Hutton' , 'Elsie Dale' , 'Elta' , Emily = 'Mycut007' (PBR) (Mystery Lady Series) , 'Emma' , 'Empress of Colwall' , 'Erica' , 'Ernest Ballard' , 'Ernie Moss' , 'Ethel Ballard' , 'Eva' , 'Eventide' , 'F.M. Simpson' , 'Fair Lady' , 'Fair Trial , 'Faith' , 'Farmington' , 'Farncombe Lilac' , 'Farncombe Wine Red' , 'Farrington' , 'Feckenham Rival' , 'Felicity' , 'Fellowship' , 'Festival' , 'Flair' , 'Flamingo' , 'Fontaine' , 'Fran' , 'Freda Ballard' , 'Freya' , 'Fuldatal' , 'Gayborder Beauty' , 'Gayborder Blue , 'Gayborder Rapture' , 'Gayborder Rose' , 'Gayborder Spire' , 'Gayborder Splendour' , 'Gayborder Splendour' , 'Gayborder Supreme' , 'Gewittersturm' , 'Glorious' , 'Glory of Colwall' , 'Goblin Coombe' , 'Goliath' , 'Grey Lady' , 'Gulliver' , 'Gurney Slade' , 'Guy Ballard' , 'Happiness' , 'Harrison's Blue' , 'Heather' , 'Heinz Richard' , 'Helen' , 'Helene' , 'Henry I Blue' , 'Herbstgruss vom Bresserhof' , 'Herbstmorgen' , 'Herbstpurzel' , 'Herbstwunder' , 'Hey Day' , 'Hilda Ballard' , 'Ibiza' , 'Ilse Brensell' , Ingrid = 'Dasing' (PBR) (Mystery Lady Series) (d) , 'Irene' , 'Isabel Allen' , 'Janet McMullen' , 'Janet Watts' , 'Janice Stephenson' , 'Jean' , 'Jean Gyte' , 'Jeanette' , 'Jenny' , Jessica = 'Dasjes' (PBR) (Mystery Lady Series) (d) , 'Jezebel' , 'Jollity' , 'Judith' , 'Jugendstil' , 'Julia' , 'Juliet' , 'Kamma Viking' , 'Karen' , 'Karminkuppel' , 'Kassel' , Kate = 'Mycut005' (PBR) (Mystery Lady Series) , Katharine = 'Daskat' (PBR) (Mystery Lady Series) ( , 'Katja' , 'Kilmersdon' , 'King of the Belgians' , 'King's College' , 'Kristina' , 'Lady Evelyn Drummond' , 'Lady Frances' , 'Lady in Blue , 'Lady in Blue' , 'Lassie' , 'Lavanda' , 'Lavender Dream' , 'Lawrence Chiswell' , 'Lederstrumpf' , 'Leona' , 'Leuchfeuer' , 'Lilac Time' , 'Lilakonigin' , 'Lisa Dawn' , 'Lisette' , 'Little Blue Baby' , 'Little Boy Blue' , 'Little Man in Blue' , 'Little Ness' , 'Little Pink Beauty' , 'Little Pink Lady' , 'Little Pink Pyramid' , 'Little Red Boy' , 'Little Treasure' , 'Lucille' , 'Lucy' , 'Mabel Reeves' , 'Madge Cato' , 'Magic White' , 'Maid of Athens' , 'Maid of Colwall' , 'Malvern Castle' , 'Malvern Queen' , 'Mammoth' , 'Margaret Murray' , 'Margaret Rose' , 'Margery Bennett' , 'Margrethe Viking' , 'Marie Ann Neil' , 'Marie Ballard' , 'Marie's Pretty Please' , 'Marjorie' , 'Marjorie Tilbury' , 'Marjory Ballard' , 'Mars' , 'Martonie' , 'Mary' , 'Mary Deane' , 'Mauve Magic' , 'May Louise' , 'Melbourne' , 'Melbourne Belle' , 'Melbourne Lad' , 'Melbourne Lad' , 'Melbourne Magnet' , 'Melbourne Mauve' , 'Melbourne Sparkler' , 'Mepri08466' (PBR) , 'Mepri08470' (PBR) , 'Michael Watts' , 'Michelle' , 'Midget' , 'Milka' , 'Minster' , 'Miranda' , 'Miss Muffet' , 'Mistress Ford' , 'Mistress Quickly' , 'Mittelmeer' , 'Moderato' , 'Monkton Coombe' , 'Mons' , 'Mount Everest' , 'Mrs George Monro' , 'Mrs J. Sangster' , 'Mrs Leo Hunter' , 'My Smokey' , 'Mycut001' (PBR) , 'Mycut002' (PBR) , 'Mycut003' (PBR) , 'Mycut004' (PBR) , 'Mycut005' (PBR) , 'Mycut007' (PBR) , 'Mypot0001' (PBR) , 'Mypot0002' (PBR) , 'Mypot0003' (PBR) , Mystery Lady Series (d) , 'Nachthimmel' , 'Nachtlicht' , 'Nachtvlinder Apolo' (PBR) , 'Nachtvlinder Bell' (PBR) , 'Nachtvlinder Caro' (PBR) , 'Nachtvlinder Dans' (PBR) , 'Nancy' , 'Neron' , 'Nesthakchen' , 'Newton's Pink' , 'Nightfall' , 'Niobe' , 'Nobilis' , 'Norma Chiswell' , 'Norman Thornely' , 'Norman's Jubilee' , 'Norton Fayre' , 'Nursteed Charm' , 'October Dawn' , 'Oktoberschneekuppel' , 'Orchid Pink' , 'Orlando' , 'Owen Tudor' , 'Owen Wells' , 'Pacific Amarant' , 'Pamela' , 'Patricia Ballard' (d) , 'Peace' , 'Peerless' , 'Penelope' , 'Pensford' , 'Percy Thrower' , 'Perry's White' , 'Peter Harrison' , 'Peter Pan' , 'Petunia' , 'Picture' , 'Picture' , 'Pink Bonnet' , 'Pink Buttons' , 'Pink Cascade' , 'Pink Gown' , 'Pink Lace' , 'Pink Perfection' , 'Pink Profusion' , 'Pink Pyramid' , 'Pink Topas' , 'Pitcote' , 'Plenty' , 'Porzellan' , 'Powder Puff' , 'Pride of Colwall' , 'Princess Marie Louise' , 'Priory Blush' , 'Priory Maid' , 'Professor Anton Kippenberg' , 'Prosperity' , 'Prunella' , 'Purple Dome' , 'Purple Dream' , 'Purple Emperor' , 'Queen Mary' , 'Queen of Colwall' , 'Queen of Sheba' , 'Rachel Ballard' , 'Ralph Picton' , 'Raspberries and Cream' , 'Raspberry Ripple' , 'Real Pleasure' , 'Rebecca' , 'Red Greetings' , 'Red King' , 'Red Robin' , 'Red Rover' , 'Red Star' , 'Red Sunset' , 'Reitlinstal' , 'Rembrandt' , 'Remembrance' , 'Reverend Vincent Dale' , 'Richness' , 'Robert' , 'Robin Adair' , 'Roland Smith' , 'Rosa Perle' , 'Rose Bonnet' , 'Rose Bouquet' , 'Roseanne' , 'Rosebud' , 'Rosebud' , 'Rosebud' , 'Rosemarie Sallmann' , 'Rosenpompom' , 'Rosenquartz' , 'Rosenschein' , 'Rosenwichtel' , 'Rosie Nutt , 'Rosy Dreams' , 'Royal Blue' , 'Royal Ruby' , 'Royal Velvet' , 'Royal Violet' , 'Royalty' , 'Rozika' , 'Ruby Glow' , 'Ruby Tips' , 'Sailing Light' , 'Sailor Boy' , 'Saint Egwyn' , 'Sam Banham' , Samoa = 'Dasthree' (Island Series) , 'Sandford White Swan' , 'Sandford's Purple' , Sandra = 'Mycut004' (PBR) (Mystery Lady Series) , 'Sarah Ballard' , 'Saturn' , 'Schneeberg' , 'Schneekissen' , 'Schneezicklein' , 'Schone von Dietlikon' , 'Schoolgirl' , 'Sheena' , Showmakers Blue Bayou = 'Zanasbluba' (PBR) , Showmakers Pretty Pink = 'Zanasprepi' (PBR) , Showmakers Snow White = 'Zanasnowhi' (PBR) , 'Sif Viking' , 'Silberblaukissen' , 'Silberteppich' , 'Silver Mist' , 'Sir Edward Elgar' , Snow Cushion , 'Snowdrift' , 'Snowsprite' , 'Sonata' , 'Sophia' , 'Sputnik' , Starletta Blue = 'Asflo Blue' , 'Starlight' , 'Steinebruck' , 'Stella Lewis' , 'Stella Lewis' , 'Sterling Silver' , 'Strahlenmeer' , 'Strawberries and Cream' , 'Sun Queen' , 'Sunset' , 'Susan' , 'Sussex Violet' , 'Sweet Briar' , 'Symbol' , 'Tapestry' , 'Taplow Spire' , 'Terry's Pride' , 'The Archbishop' , 'The Bishop' , 'The Cardinal' , 'The Choristers' , 'The Dean' , 'The Rector' , 'The Sexton' , 'The Urchin' , 'Thora Perry' , 'Thundercloud' , 'Timsbury' , Tonga = 'Dasfour' (Island Series) , 'Tony' , 'Tosca' , 'Tovarich' , 'Triumph' , 'Trudi Ann' , 'True Blue' , 'Twinkle' , 'Vice Regal' , 'Victor' , 'Victoria Alma' (PBR) , 'Victoria Betty' (PBR) , 'Victoria Celeste' (PBR) , 'Victoria Diana' (PBR) , 'Victoria Elisabeth' , 'Victoria Emma' (PBR) , 'Victoria Fanny' (PBR) , 'Victoria Gaby' (PBR) , 'Victoria Hillary' (PBR) , 'Victoria Ilona' (PBR) , 'Victoria Ilona Bicolor' , 'Victoria Jane' (PBR) , 'Victoria Kate' (PBR) , 'Victoria Laura' (PBR) , 'Victoria Mathilde' (PBR) , 'Victoria Nathalia' , 'Victoria Ofelia' (PBR) , 'Victoria Paula' (PBR) , 'Victoria Pink Fanny' (PBR) , 'Victoria Purple Fanny' (PBR) , 'Victoria Queen' (PBR) , 'Victoria Red Gaby' , 'Victoria Rita' (PBR) , 'Victoria Sara' (PBR) , 'Victoria Ulla' (PBR) , 'Victoria Vera' , 'Victoria Wilma' (PBR) , 'Vignem' , 'Violet Lady' , 'Violetta' , 'Walkden's Pink' , 'Waterperry' , 'Weisses Wunder' , 'Wells' White' , 'White Gypsy' (PBR) , 'White Ladies' , 'White Swan' , 'White Wings' , 'Wickwar Crimson' , 'Winford' , 'Winsome Winnie' , 'Winston S. Churchill' , 'Zanasbluba' (PBR) , 'Zanashopi' (PBR) , 'Zanasnowhi' (PBR) , 'Zanasparro' (PBR) , 'Zanasprepi' (PBR) , 'Zwergenhimmel'

(1) Symphyotrichum novi-belgii (Linnaeus) G. L. Nesom var. crenifolium (Fernald) Labrecque & Brouillet

　　synonym　Aster novibelgii Linnaeus var. crenifolius (Fernald) Labrecque & Brouillet

　　synonym　A. crenifolius (Fernald) Cronquist
　頑強で小型。茎は無毛(ときに上部の線に粗毛がある)。葉身は広い卵形～長円形、長さは幅の4～5倍、基部は強く抱く。2n = 48。花期は8～9月。

(2) Symphyotrichum novi-belgii (L.) G. L. Nesom var. elodes (Torr. & A. Gray) G. L. Nesom

　　synonym　Aster elodes Torr. & A. Gray
　植物は比較的に細く、頑強、小型ではない。茎は普通、無毛、上部は線上にわずかに粗毛がある。葉身は線状披針形、長さは幅の10+倍、基部は類抱茎。2n=48。花期は8～10月。

(3) Symphyotrichum novi-belgii (L.) G. L. Nesom var. novi-belgii

　　synonym　Aster novi-belgii L.
　植物は普通、細く、ときに頑強、しかし、極小型ではない。茎は無毛又は線上に粗毛がある。葉身は卵状披針形又は披針形～倒披針形、長さは幅の7～9倍、基部は±抱茎。2n=48。花期は8～9月。

(4) Symphyotrichum novi-belgii (L.) G. L. Nesom var. villicaule (A. Gray) Labrecque & Brouillet

　　synonym　Aster johannensis Fernald
　　synonym　Aster longifolius var. villicaulis A. Gray

　　synonym　Aster novi-belgii var. villicaulis (A. Gray) B. Boivin

　植物は比較的、細く。茎は均等に、密に粗毛がある(少なくとも、下部に)。葉身は披針形～線状披針形、長さは幅の7～9倍、基部は抱茎。2n = 48。花期は8～9月。

参考

1) Flora of China
　Symphyotrichum( S. retroflexum , S. ciliatum , S. subulatum) 2）GRIN
　Symphyotrichum 3) Flora of North America
　Symphyotrichum 4)Jepson eFlora: Taxon page
　Symphyotrichum chilense 5）Asteraceae
　Asteraceae Bercht. et J.Presl (キク科), aster family